Free Project Circuit Diagram

Battery Powered Burglar Alarm Circuit

2011-10-08T17:58:00.000+07:00

Here’s a design circuit for single zone alarm - with independently adjustable Exit, Entry and Siren Cut-Off timers. It will accommodate the usual types of normally-closed input devices - such as magnetic-reed contacts, foil tape and PIRs. This is the figure of the circuit;

The alarm is easy to operate. Sw1 can be any type of two-way switch. If the Buzzer sounds when you switch the alarm on - the normally-closed loop is open. Switch off again - and check the building for open doors or windows. If the Buzzer does not sound - the loop is intact. Depending on the setting of R3 - you have up to about a minute to leave the building. As you do so - the Buzzer will sound. When you close the door behind you - it should stop sounding. This confirms that the loop has been restored within the time allowed. When you return and open the door - the Buzzer will sound. Depending on the setting of R4 - you have up to about a minute to switch the alarm off. If you fail to do so - the Siren will sound. Depending on the setting of R5 - the Siren will sound for up to about 20-minutes. Then it will switch off - and remain off. Of course - you can stop the noise at any time by moving Sw1 to the "off" position.

5VDC to 12VDC LT1070 Boost Converter Circuit

2011-09-27T11:23:00.000+07:00

Here’s a design circuit for 5VDC to 12VDC boost converter circuit built based LT1070. This is the figure of the circuit;

The LT®1070/LT1071 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, fly back, forward, inverting and “Cuk”. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry.

Wide Band High Frequency Amplifier Circuit

2011-08-27T11:49:00.000+07:00

Here’s a circuit for high-frequency amplifier circuit using wide frequency band between 75-150 MHz with transistors, a PNP amplifier. To enhance the signal strength. Before the receiver of the phone. Or FM radio or amateur radio. If high-frequency signals, in particular, its VHF. The booster circuit is one, serves to amplify the signal strength only. This is the figure of the circuit;

Operation of the circuit. High-frequency range VHF, inductive antenna, to the emitter pin of the transistor Q1. so circuit held, in conjunction with the bass, a nice low output impedance. You can use a special access code 50 ohms, the antenna on the circuit at all. Signal at the Q1 will be expanded to increase. And sent to a tuner or receiver to the receiver. The L1 coil wire enamel No. 24 SWG, thousands of rounds of 10, inside diameter 3 mm. And the coil L2 wire number. Thousands of 13 turns, diameter 5 mm. Stent both as a non-core, or an air core. The power supply is +5 V, this circuit while current is 2.5 mA. If the components to use. Should be based on the antenna. And design of high frequency printed circuit boards as well.

True Stereo Indicator Circuit for Detects L-R Signal Difference

2011-08-27T11:46:00.000+07:00

This circuit is true stereo indicator is different from what we usually find on FM radio receiver, which is usually a pilot tone detector. A stereo broadcast from FM radio station contain pilot tone, but a presence of pilot tone doesn’t necessarily a stereo broadcast signal since a mono FM transmitter ca broadcast pilot tone as well. This is the figure of the circuit;

Since this circuit to detect the difference between left and right channel, this circuit can detect a real stereophonic programs. When there is no difference between R and L input signals, the output A1 and output A2 is at the same potential. That will make a a virtual ground rail at half the supply voltage. The A1 will supply a negative or positive voltage when A1 detects a difference between R and L input signals with respect to the virtual ground rail. The C4 will be charged via D2 an C3 via D1. The LED is turned on by the comparator A3/A4 via OR circuit D3/D4. The input signal level should be greater than 100mV to compensate for the drop across D2 or D1. P1 is used to adjust the sensitivity of stereo indicator.

TDA1514 Audio Amplifier Circuit

2011-08-27T11:44:00.000+07:00

Here’s a circuit for TDA1514 audio amplifier circuit that is capable to provide a high audio power output using a specialized audio IC and other few common components. The TDA1514 audio IC is manufactured by Philips Semiconductor and is capable to provide an output audio power up to 50 W. TDA1514 50W audio amplifier supports 4 or 8 ohms loads and require few external components. This is the figure of the amplifier circuit diagram;

This 50W audio amplifier support a wide input voltage range from 10 volts up to 30 volts and it has many other build in features like: low harmonic distortion, low inter modulation distortion, low offset voltage, good ripple rejection, mute/stand-by facilities, thermal protection, protected against electrostatic discharge, very low thermal resistance, Safe Operating Area (SOAR) protection.

15 Channels Cascaded MAX455 Video Mux

2011-08-27T11:43:00.000+07:00

Here’s a circuit for showing two MAX455s IC chip are cascaded to build a 1 of 15 video Multiplexer. This is the figure of the circuit;

This cascading is done by connecting the output of one MAX455 MUX to one input of a second MAX455 MUX. The output of the first MUX should be terminated to ground using a 75R resistor, to preserve bandwidth although the two devices are usually close to one another.

Discrete Sliding Tone (Frequency Ramp) Doorbell Circuit

2011-08-20T10:47:00.000+07:00

Here’s a circuit for doorbell circuit produces a low tone that will slide up to higher frequency. The equivalent total resistance connected between the base of Q1 and ground (Rbg), and coupling capacitor C1 determines the AF oscillator’s frequency. The resistance (Rbg) is equal to (R2+R1)R3. This is the figure of the circuit;

The R2 is used to set the initial bias condition, adjusted to produce a pleasant low starting frequency doorbell tone. D1 will start to conduct when Capacitor C3 charge through R6 until it reaches D1 bias voltage level. Then the value of Rbg is paralleled by R4 and D1, and R5-D2-D3, and the values of diode’s equivalent resistance is gradually decreased as the C3 voltage ramp up. This decreasing resistance value make the output tone slides up in frequency. Two different diode path is provided to extend the linear area of diode conduction transition slope. With two path with different biases, after the single diode path has saturated, the second path provide further linear increase at higher voltage level.

PLL Oscillator for Medium Wave Application Circuit

2011-06-06T08:15:00.000+07:00

PLL oscillator is used to get very stable frequency woth very low distortion of sine wave output. The stability is equal to crystal-based oscillator, and the low distortion level of the sine wave output is equal to LC based oscillator. The method of PLL control in PLL oscillator is done by adjusting the frequency of sine wave VCO (voltage controlled oscillaltor). The VCO is an LC based oscillator, but the capacitor is not a fixed one, but it’s a varactor, a variable capacitor which its capacitance value is variable depends on the applied voltage.

The control of this voltage change the frequency of the VCO. This voltage control is coming from a phase difference detector that detect the phase difference between the crystal reference clock and the VCO output. If the frequency of the VCO output is different then the error signal from the phase difference detector will try to correct the VCO until the VCO has the same frequency and the phase difference is slipped at certain level to produce the voltage control that maintain the VCO frequency.

Multiplying PLL Oscillator’s Output Frequency

To get the frequency higher than the PLL oscillator’s internal reference clock, we just need to insert a frequency divider between the VCO and the phase difference detector. Using this method, now the PLL control system will maintain the divided VCO output frequency to be same with the reference, so the PLL Oscillator that come directly from the VCO has the frequency of the reference frequency multiplied by the division value of the programmed divider.

PLL Oscillator Circuit

This is the figure of the oscillator circuit;

Simple PLL oscillator circuit can be constructed using MC145106 IC, and it need only external VCO to produce a sine wave output. The crystal frequency is 4608 kHz for European medium wave frequency spacing standart, and 5120 for USA. The power supply must be regulated and well decoupled.

TDA7850 Car Power Amplifier Circuit

2011-05-23T04:52:00.000+07:00

Here’s a design circuit for very simple class AB power amplifier designed in MOSFET technology which use just few external components. Tda7850 power amplifier can be used in car radio audio systems. This is the figure of the circuit;

MOSFET output power stage, Hi-Fi class distortion, Low output noise, ST-BY function, Mute function, auto mute at minim supply voltage detection, Output short circuit to ground, to Vs protection, Overrating chip temperature with soft thermal limiter, Output DC offset detection. The TDA7850's inputs are ground-compatible and can stand very high input signals (±8Vpk) without any performance degradation. Standby and Muting facilities are both CMOS compatible. In true CMOS ports or microprocessors are absent the ST-BY pin can be connected direct to Vs but it’s necessary to connect a 470kΩ resistance between these two pins (Vs and ST-BY). The power supply for TDA7850 power amplifier must be 14.4 volts. The TDA7850 IC must be mounted on a corresponding heat sink for high temperature dissipation.

TDA2005 Audio Amplifier Circuit

2011-05-23T04:36:00.000+07:00

Here’s a circuit for car radio audio amplifier circuit is specially designed to work on devices like: car radios, cd-players and similar devices. The car radio audio amplifier circuit is based on the TDA2005 audio IC which can provide a maximum output power of 20 watts into a 4 ohms load, connected in bridge mode configuration. This is the figure of the circuit;

The TDA2005 audio amplifier IC can work in even in bridge mode or stereo mode configuration. The TDA2005 audio IC is a class B audio amplifier designed in a Multiwatt 11 package and can be ordered in two types TDA2005M used for bridge mode application or TDA2005S used in stereo applications. If the TDA2005 is used in stereo mode it can deliver a 10 + 10 watts output power in a 2 ohms load. The advantage of using the TDA2005 audio amplifier in bridge mode configuration is that the total harmonic distortion (THD) is 1% and the THD for the stereo configuration mode is 10 %. The Tda2005 audio amplifier IC supports a wide range of input voltage from 8 volts up to 18 volts. The TDA2005 main features are: short circuit protection, overrating chip temperature, low external components required , bridge or stereo booster amplifiers with or without boostrapand with programmable gain and bandwidth , no electrical isolation between the package and the heat sink .

Switchstart Ballast Circuit for Fluorescent Tube Lamp

2011-05-23T04:33:00.000+07:00

Simplicity, low cost and improved efficiency when compared with the alternative options are the reasons why the switch start circuit has been widely adopted. Moreover, the 230V mains voltage is sufficiently higher than tube running voltage to let the use of the simple series impedance ballast in almost every case. Where the mains voltage is not high enough, for example in most 120V supplied circuits, a quick start circuit incorporating voltage step-up is used to control the lamp. This is the figure of the circuit;

The lamp doesn’t light on first when the voltage is applied to the circuit, so the full mains voltage shows up across the starter via the choke and lamp cathodes. The starter is made of bi metallic contacts sealed within a small discharge bulb with an inert gas filling. The gas could be argon or neon. A glow discharge within the starter is caused by the mains voltage. This will heats up the bi metallic contacts, causing them to approach each other. When the bi metallic stay close, this will let preheat current to run through the choke and both cathodes.

The bi metallic contacts cool down and open since the glow discharge within the starter has now ceased. The voltage across the lamp increases rapidly and hit the lamp because the inductance of the choke tries to preserve current flow. The starter’s contacts close again and the cycle repeats if it doesn’t happen. Current and voltage are controlled by the choke to the correct levels since the lamp has started at the first time. The lamp running current is enough to maintain the cathodes (heaters) hot and sending out electrons without the need for separate heater supplies, which would otherwise be wasteful of energy. The circuit remains open because there is not enough voltage to cause a glow discharge in the starter since the lamp’s running voltage is much less than the mains voltage. Leading current from the mains is drawn by power factor correction (PFC) to counterbalance for the lagging current drawn by the lamp circuit. [Circuit diagram source: NXP Application Note]

Pink (Flicker) Noise Generator Circuit

2011-05-23T04:18:00.000+07:00

Here’s a design circuit for a flicker noise generator, an implementation of flicker noise analog modeling presented in NBS technical note #604, “Efficient Numerical and Analog Modeling of Flicker Noise Processes” by J.A. Barnes and Stephen Jarvis, Jr. With the component values shown the schematic diagram, the circuit will give a 1/f noise slope from below 1Hz to over 4KHz. A TLC2272 op-amp is used for this circuit, but any low noise op-amps will work. This is the figure of the circuit;

The op-amp must be a low noise type because the noise generation come from a high value resistor generating about 50nV noise. Use an op-amp with noise voltage less than 15 nV/root-Hz and noise current less than 0.1 pA/root-Hz, an easy-to-find feature in many low-noise modern op-amp devices. To simplify the construction, the capacitor values is slightly different from the calculated values described in the paper, and a bias circuit is provided to allow the use of polarized electrolytic capacitor. Because the electrolytic capacitor has poor tolerance, it should be chosen carefully for best performance. Compared to circuit utilizing deode zener, reverse-biased transistor, or other noisy devices, this circuit give more predictable and repeatable output level. If we tap the output of the first op-amp through a 100uF capacitor (like as seen in the second op-amp), a precise 5uV/root-Hz white noise will be there as an excellent signal source for audio noise measurement calibration. At the second op-amp, this white noise is filtered to give a flicker noise (pink noise) frequency spectrum, since the pink noise is a subset of white noise in the frequency domain. [Circuit diagram source: techlib.com]

Single Chip Theremin Circuit

2011-04-19T20:04:00.000+07:00

This is a design circuit for a single chip Theremin circuit. Theremin is an electronic music instrument which sense hand movement to control the tones/frequency. This Theremin circuit uses two separate Colpitts LC oscillators to produce a beat frequency. The frequencies of two Colpitts LC oscillators are mixed and then rectified. This rectification demodulate the mixed signal to get the beat frequency which is in audible range. This is the figure of the circuit;

This beat frequency or difference is the real Theremin’s output. The oscillator is operated at high frequency (inaudible) to get wide audible frequency range of beat frequency when two oscillator output is mixed. This circuit uses a 4011 quad gate to construct the high frequency oscillator operating at 250kHz. The metal probe that is used to sense your hand produces only small frequency shift in term of percentage of original frequency, that’s why we need to derive the beat frequency to get wide audible frequency range as the result of high frequency shifting. The IC2, an LM741 is used to amplify the mixed signal before rectification. The D1 will rectify the mixed signal to detect the audio (the beat frequency). This audio signal is then filtered by an adjustable band pass filter IC3. The further audio amplification before power amplifier IC5 is done by IC4. The metal toilet-tank float is used for the hand probe since is has better sensitivity than a simple wire antenna, but any conductive material will work. [Circuit diagram source: seekic.com]

Vehicle Interior Lighting With Switch-Off Delay

2011-02-21T10:55:00.000+07:00

This is a circuit for a switch-off delay for the vehicle interior lighting is a naturally a standard feature. However, with certain models having only spartan ﬁttings, or older-model vehicles, you’re left sitting in the dark as soon as you climb in and close the door. Here’s the figure of the circuit;

That calls for an aftermarket accessory! The author built this circuit using ‘normal’ components (with leads), but in the SMD manner, which means ﬁtting the components on the copper side. The only holes drilled in the circuit board were the four ﬁxing holes, and the entire assembly was ﬁrmly attached to the surface of the heat sink for power transistor T3 (the author used a finned heat sink rated at 7.2 °C/W). The heat sink is at ground potential. A value of 1 Ω was used for R3 with satisfactory operation of the darlington. The light goes on when the door is opened. After the door is closed, it continues to illuminate the interior of the car at full brightness for around 30 seconds, after which it slowly dims. Approximately 1 minute after the door is closed, the quiescent current drops to zero.

1100 Mhz Divider Circuit

2011-02-21T10:53:00.000+07:00

This is a design circuit for divider circuit that is used in many RF applications like as satellite receiver, digital tuners, frequency counters, PLL, etc. Here’s the figure of the circuit;

The heart of circuit is an IC named SAB6456, but you can use SDA2101 or other equivalent chips. Each output is NOT of the other.

Wide Band Two Pole High Pass Filter Circuit

2011-02-07T20:21:00.000+07:00

This is a circuit for high input impedance of the LH0033 and LH0063 are suitable for active filter applications. A basic two pole, high pass filter is diagrammed in circuit using the LH0033. Here’s the figure of the circuit;

This circuit provides a 10 MHz cutoff frequency. One consideration of the filter is its apparent gain change due to the finite output impedance of the amplifier, which affects the overall gain and the damping factor of the filter stage. Resistor R3 ensures that the input capacitance of the amplifier does not interact with the filter response at the frequency of interest. An equivalent low pass filter is similarly obtained by capacitance and resistance transformation. [Circuit diagram source: National Semiconductor Application]

Photodiode Amplifier Circuit

2011-02-07T20:12:00.000+07:00

All photo generators display some voltage dependence of both speed and linearity. It is obvious that the current through a photoconductive cell will not display strict proportionality to incident light if the cell terminal voltage is allowed to vary with cell conductance. Somewhat less obvious is the fact that photodiode leakage and photovoltaic cell internal losses are also functions of terminal voltage. This is a circuit that can be used for amplifier the photo diode;

The current to voltage transducer circuit neatly sidesteps gross linearity problems by fixing a constant terminal voltage, zero in the case of photovoltaic cells and a fixed bias voltage in the case of photoconductors or photodiodes. [Circuit diagram source: National Semiconductor Application]

Low Power Universal Demultiplexer/Decoder

2011-02-05T01:37:00.000+07:00

This is a circuit for universal decoder that has functions as either a dual 1-of-4 decoder or as a single 1-of-8 decoder, depending on the signal applied to the Mode Control (M) input. Here’s the figure of the test circuit;

In the dual mode, each half has a pair of active-LOW Enable (E) inputs. Pin assignments for the E inputs are such that in the 1-of-8 mode they can easily be tied together in pairs to provide two active-LOW enables (E1a to E1b, E2a to E2b). Signals applied to auxiliary inputs Ha, Hb and Hc determine whether the outputs are active HIGH or active LOW. In the dual 1-of-4 mode the Address inputs are A0a, A1a and A0b, A1b with A2a unused (i.e., left open, tied to VEE or with LOW signal applied). In the 1-of-8 mode, the Address inputs are A0a, A1a, A2a with A0b and A1b LOW or open. All inputs have 50 kX pull down resistors. [Circuit diagram source: National Semiconductor Application Notes]

Op Amp Digital to Analog Converter Circuit

2011-01-31T05:50:00.000+07:00

This is a design of the simple 4-bit digital-to-analog converter. It is actually just a variant of a simple op amp summer circuit, i.e., an operational amplifier configured to output a voltage that is proportional to the sum of the input voltages. Here’s the figure of the circuit;

In this circuit, the inputs are binary weighted with respect to each other, with the binary weighting of the inputs achieved by the R-2R ladder resistor network at the non-inverting input of the op-amp. As its name implies, the R-2R network consists of resistors with only two values, R and 2R (10K and 20K, respectively, in the circuit shown). The input SN to bit N is '1' if it is connected to a voltage VR and '0' if it is grounded. The number of bits of this DAC may be increased by connecting more switches with corresponding R/2R resistors.

LM134-LM10 Thermometer/Temperature Sensor Circuit

2011-01-31T05:49:00.000+07:00

This circuit is use to build a thermometer which has -55 to 150°C sensing range. The ideal meter for this circuit is a 0-200uA digital ampere meter, which can show both positive and negative polarity. This will make the circuit suitable for indicating temperatures below 0°C. Here’s the figure of the circuit;

This circuit is based on LM134 and LM10 that has basically a current source with very accurate and consistent temperature coefficient, so many temperature sensing application find it suitable for the sensor. [Circuit diagram source: National Semiconductor Notes]

LM10 Single Cell Microphone Amplifier Circuit

2011-01-31T05:48:00.000+07:00

This is a design circuit for a Single-cell microphone amplifier circuit. This circuit produces a voltage gain of 60 dB at 500Ω load with bandwidth 5 kHz. This circuit can provide a 60dB gain up to 10 kHz if it is unloaded. This circuit has a 10 kΩ input impedance. Here’s the figure of the circuit;

This circuit cannot neither produces an output swing closer than 800mV or below 150mV to the supply. However this circuit still has an input noise of 40 to 50 nV/√Hz. [Circuit diagram source: National Semiconductor Application Notes]

Subwoofer Filter Circuit

2011-01-30T07:19:00.000+07:00

This is a circuit of subwoofer active filter circuit is a 24 dB octave filter with a Bessel character and cutoff frequency of 200 Hz. So, if you are interested in experimenting with audio circuits in subwoofer range, this circuit is for you. This is the figure of the circuit;

In subwoofer range, all audio frequencies below 200 Hz can be fed to a single speaker box since the human directional perception of sound diminishes at this frequency range. The normal stereo signals above 200 Hz can be fed to two satellite speaker boxes. How does the subwoofer filter works: A1 and A2 buffer the signals coming from right and left channels. Op amp combinations A2/A4 and A9/A10 function as the high pass filters. The outputs are then connected to the final amplifiers of the battelite boxes. Signals from both channels are fed to A5. Op amps A6/A7 function as the low pass filter, A8 as the output amplifier for the subwoofer signal.

The signal level can be balanced between the subwoofer and the satellite lines. The power needed for this filter circuit must ne a symmetrical power supply. The op amps can have either JFET or bipolar inputs.

Smart Heater Controller Circuit

2011-01-30T07:14:00.000+07:00

This is a design circuit of the electronic heater controller presented here is built around the renowned 3-Pin Integrated Temperature Sensor LM35 (IC1) from NSC. Besides, a popular BiMos Op-amp CA3140 (IC2) is used to sense the status of the temperature sensor IC1, which also controls a solid-state switch formed by a high power Triac BT136(T1). This is the figure of the circuit;

Resistive type electric heater at the output of T1 turns to ON and to OFF states as instructed by the control circuit. This gadget can be used as an efficient and safe heater in living rooms, incubators, heavy electric/electronic instrument etc. Normally, when the temperature is below a set value (Decided by multi-turn preset pot P1), voltage at the inverting input (pin2) of IC1 is lower than the level at the non-inverting terminal (pin3). So, the comparator output (at pin 6) of IC1 goes high and T1 is triggered to supply mains power to the desired heater element.

When the temperature increases above the set value, say 50-60 degree centigrade, the inverting pin of IC1 also goes above the non-inverting pin and hence the comparator output falls. This stops triggering of T1 preventing the mains supply from reaching the heater element. Fortunately, the threshold value is user-controllable and can be set anywhere between 0 to 100 Degree centigrade.

High Impedance Voltmeter Circuit

2011-01-30T07:12:00.000+07:00

This is the design circuit off ideal voltmeter has infinite input impedance, meaning that it draws zero current from the circuit under test. This way, there will be no "impact" on the circuit as the voltage is being measured. The more current a voltmeter draws from the circuit under test, the more the measured voltage will "sag" under the loading effect of the meter, like a tire-pressure gauge releasing air out of the tire being measured: the more air released from the tire, the more the tire's pressure will be impacted in the act of measurement. This loading is more pronounced on circuits of high resistance, like the voltage divider made of 1 MΩ resistors. This is the figure of the circuit;

If you were to build a simple 0-15 volt range voltmeter by connecting the 1 mA meter movement in series with the 15 kΩ precision resistor, and try to use this voltmeter to measure the voltages at TP1, TP2, or TP3 (with respect to ground), you'd encounter severe measurement errors induced by meter "impact:" If we were to increase the meter's input impedance, we would diminish its current draw or "load" on the circuit under test and consequently improve its measurement accuracy. An op-amp with high-impedance inputs (using a JFET transistor input stage rather than a BJT input stage) works well for this application.

Note that the meter movement is part of the op-amp's feedback loop from output to inverting input. This circuit drives the meter movement with a current proportional to the voltage impressed at the non-inverting (+) input, the requisite current supplied directly from the batteries through the op-amp's power supply pins, not from the circuit under test through the test probe. The meter's range is set by the resistor connecting the inverting (-) input to ground.

Build the op-amp meter circuit as shown and re-take voltage measurements at TP1, TP2, and TP3. You should enjoy far better success this time, with the meter movement accurately measuring these voltages (approximately 3, 6, and 9 volts, respectively).

Audio Controlled Incandescent Lamp Light Controller

2011-01-30T07:09:00.000+07:00

This is a design circuit for an audio-controlled lamp circuit. This circuit requires low voltage input such as pre-amplifiers, tone control, or general audio line level output. It’s also possible to feed the input with signal from small power amplifier output, or high power amplifier witk low volume level. The characteristic of lamp dimming (incandescent lamp) will look like coming from proportional controller since the switching rate of the TRIAC would be much higher than the lamp dimming response. This is the figure of the circuit;

If the lamp won’t go off after the audio signal back down to zero, then try to adjust the potentiometer. You can use filament transformer (usually used for tube), or you can also use small tv-antenna-booster transformer (20v-220V), or other small transformer below 500mA. Don’t worry if you can’t fine transformer with exact primary-secondary ratio, since the potentiometer is there for fine adjustment, and you can always change the input voltage level of the audio input signal.

555 Timer Voltage Controlled Oscillator Circuit

2011-01-30T07:01:00.000+07:00

This is a circuit of a voltage-controlled oscillator (VCO) that uses the 555 timer IC as the main component. As expected, the 555 timer is configured as an astable multi vibrator to be able to serve as an oscillator. An astable multi vibrator is just a timing circuit whose output oscillates between 'low' and 'high' continuously, in effect generating a train of pulses. This is the figure of the circuit;

The difference of this circuit with the basic 555 astable circuit is that its 555's pin 5 is tied to an external voltage source. Pin 5 is the 555's control voltage pin, which allows the user to directly adjust the threshold voltages to which the pin 2/pin 6 input voltages are compared by the 555's internal comparators. Since the outputs of these comparators control the internal flip-flop that toggles the output of the 555, adjusting the pin 5 control voltage also adjusts the frequency at which the 555 toggles its output. Increasing the input voltage at pin 5 decreases the output oscillation frequency while decreasing the input voltage increases the output oscillation frequency.

Voltage Controlled Stereo Volume Control Using LM13600 OTA

2011-01-24T16:23:00.000+07:00

This is the design circuit for control our audio using a DAC which is controlled by a microcontroller, or we can use mono potentiometer with RC filter to minimize the scratched sound produced by a dirty potentiometer (I see this method in one of SONY audio products). Using a voltage-controlled volume control enables you to design your own tremolo effect, noise gate, dynamic compressor-expander effect and many more! This is the figure of the circuit;

This circuit uses excellent matching of the two LM13600 operational trans-conductance amplifier (OTA), providing 0.3dB channel-to-channel gain tracking (typical) volume control. Potentiometer RP is used to adjust the output offset voltage, and can be substituted by two 510R fixed resistors if you use the circuit in AC-coupled application. With the value shown in the diagram, the gain of the amplifier (Vo/Vin) = 940*IABC. [Circuit diagram source: National Semiconductor Application Notes]

Mic/Guitar Compressor Circuit Using Transistor Bias Control

2011-01-24T16:19:00.000+07:00

This is a design circuit for compressor circuit that can be used for dynamic mic, condenser mic, or electric guitar pickup. This circuit doesn’t produce very good sound output, but it has very stable amplitude/volume. This compressor circuit design is unique since it uses base current control for manipulating the gain. This is the figure of the circuit;

The first and second transistor is an ordinary pre-amplifier, but the first transistor’s bias is controlled by the output signal to get a negative feedback. The third transistor is employed to control the dc voltage level at the junction of 1M resistor and 10uF cap that provide the first transistor bias current. The control mechanism is also unique, where a full dc level at the capacitor is discharged at each half cycle of output when it exceed the base forward bias. The gain control method by decreasing the base bias current of first transistor near its cut-off point produce a distortion, which might be unacceptable by some people especially for music/singing, but can be acceptable for public address. For electric guitar application, this compressor can be a good option since the distortion characteristic gives a unique effect, and the overshoot and undershoot of the amplitude stabilization gives something similar to “wow” effect from old recording.

Ice Warning And Light Reminder Circuit

2011-01-24T16:13:00.000+07:00

This is a design circuit for very simple ice warning and lights reminder electronic. This device will tell a driver if his lights should be on and will warn him if the outside temperature is nearing zero by lighting a LED and sounding a buzzer. This is the figure of the circuit;

Using the VR1 you can adjusts sensitivity for temperature and using VR2 you can adjust sensitivity for the light. Both thermistor and LDR should be well protected. More high gain NPN transistors will work for this electronic project. For this electronic project you can use BC108 type transistor or some other NPN high gain transistor. This ice warning and lights reminder electronic project must be powered from a 12 volt DC power supply circuit.

Color Organ Electronic Circuit Using LM3909 IC

2011-01-24T16:09:00.000+07:00

Using LM 3909 LED flasher IC, can be designed various electronic projects. As you can see in this circuit diagram, using the LM3909 LED flasher IC can be designed a very simple color organ. But this circuit is not complicated, it use just some common active audio filters for filtering audio signals and a part formed by a LM3909 IC. This is the figure of the circuit;

All of three active filters drives the audio spectrum into three bands drive rectifiers and then drive IC2,3 and 4, flashing the LEDs at 6 Hz. D4,D5 and D6 should be three different colors for best effect. In the table bellow you can see all electronic parts required by this color organ project.

Two Stage Phono Pre-Amplifier Circuit with Very Accurate RIAA Response Curve

2011-01-20T19:33:00.000+07:00

This is a design circuit that can be used to produce a pre-amplifier with accurate RIAA response, this circuit use two stages of amplifier. This circuit is more complex than single op-amp RIAA pre-amp, but the performance is excellent in terms of accurate frequency response. This is the figure of the circuit;

The circuit uses LM833 high performance op-amp from National Semiconductor, giving the best performance of 0.1 dB response curve error, compared to the standard RIAA curve. [Circuit diagram source: National Semiconductor Application Notes]

Signal Conditioning Amplifier Circuit for Piezofilm Sensor

2011-01-20T19:29:00.000+07:00

This circuit is design for the signal can be converted by piezoelectric films in many ways such as thermal to electrical (temperature sensor), mechanical to electrical (microphone), and electrical to mechanical (a loudspeaker). The circuit is signal conditioning amplifier for piezofilm sensor which uses three op amps and has a high-input-impedance differential charge. This is the figure of the circuit;

This circuit uses a voltage source with a capacitor in series as the electrical analog of a piezofilm sensor. The differential charge amplifier is endowed by a dual op amp (IC1) with low supply current and single-supply operation. The input common-mode voltage is set by a small bypass capacitor (C3), R2, R1 at the mid-supply level. The C1 and C2 are used to set AC gain for the differential stage. A gain of C1/CEQ is 96.

The differential amplifier also is used to act as a first-order high-pass filter. The resistors R9, R8, R6, and R5 with IC2 perform differential-to-single-ended conversion. Using the values shown, the different gain is 20. [Circuit diagram source: maxim-ic.com]

One Second Steps 555 Timer Circuit (0 To 59 S)

2011-01-20T19:27:00.000+07:00

This is a design circuit for the linearity of 555 IC is sufficient to make 1 second precision, and this circuit employs the feature in this design. This timer step circuit can generate a timing steps from 0 to 59 s in 1-s intervals. This is the figure of the circuit;

Flame Detector Using Platinum-Rhodium Thermocouple

2011-01-20T19:26:00.000+07:00

In furnace operation, it is necessary to make sure that the fuel or gas is ignited properly by detecting the flame. If there’s no flame detected, the situation can be dangerous if the furnace is flooded with explosive gas, so the fuel/gas supply valve should be closed automatically to avoid catastrophic disaster. A thermocouple can be use to detect flame. This is the figure of the circuit;

A platinum-rhodium thermocouple produce 8mV output at 800 °C. You can see the thermocouple is connected directly to the positive and negative inputs, look like there’s no threshold, but wait, the balance input (pin 5) is connected to the reference output and this gives the threshold. [Circuit diagram source: National Semiconductor Application Note]

Fan Speed Control: Turn On Your Fan Only When Needed

2011-01-20T19:24:00.000+07:00

If you have to provide a fan to cool your audio power amplifier final transistor, it better to turn it off when it’s not needed. This solution is good since you don’t have to hear the fan noise when you play the music with low level volume at night, the power transistor won’t get hot. When you start turning your volume control toward maximum level, your power chip/transistor begin getting hotter and this circuit will turn on the fan to cool the heat sink. You won’t hear the fan noise because now your music is getting much louder. This is the figure of the circuit;

The temperature sensor (NTC, negative temperature coefficient thermistor) should be placed as close as possible to the power transistor or IC. Installing it on the heat sink is good idea, just make sure a tight thermal contact and locate it close to the power transistor/IC.

If you have a thermometer, you can set the VR1 at heat sink temperature about 70 Celsius degree. Lowering this setting it’s OK but you might hear the fan noise although you only use your amplifier to play music for mild volume level. What if you don’t have a thermometer but you want your power amplifier safe? The following technique can be use but use at your own risk: use your amp for loud volume and use your finger to regularly touch the heat sink and adjust VR1 to activate the fan at heat intensity where it’s the maximum you can stand to touch. The LED indicator will give you the information that the fan is active. Stay cool with your amplifier!

Anti-Log Converter Circuit

2011-01-20T19:22:00.000+07:00

Anti-log or exponential generation is simply a matter of rearranging the logarithmic circuitry. The circuitry of the log converted to generate an exponential output from a linear input. This is the figure of the circuit;

The emitter of Q2 in proportion to the input voltage is driven by amplifier A1 in conjunction with transistor Q1. The collector current of Q2 varies exponentially with the emitter-base voltage. [Circuit diagram source: National Semiconductor Application Note]

Radio Frequency (RF) Watt Meter Circuit

2011-01-06T19:26:00.000+07:00

This is a circuit for RF (radio frequency) transmitter experiment, watt meter is useful for optimizing the transmitter circuit. A simple RF watt meter circuit is shown in the schematic diagram below. Because circuit is not frequency sensitive, calibration is accurate on all HF bands. The sensitivity is affected by meter movement, number of turns in primary coil, and resistive voltage driver. This is the figure of the system;

Pots can be adjusted for full-scale values from 1-14 W with values shown on the diagram. C1 and C2 are 3-20 pF. Diodes are 1N34A, 1N60, or equivalent. L1 is 46 turns No. 28 on Amidon T-50-2 toroid, with 2 turns No. 22 between ends of L1 for L2. Connect resistive dummy load to one coax receptacle and RF power source to other to adjust, with R2 at maximum resistance. We can provide highest meter reading and make that the FWD position with place the switch on the upper position. Switch to other position, which becomes REF, and for null reading, adjust C1. Reverse RF source and load, leaving switch at FWD, and adjust C2 for null. Now, we can calibrated the Wattmeter.

Power Sequencer Circuit Using LM3880

2011-01-06T19:25:00.000+07:00

This is a design circuit for Power Sequencer offers the easiest method to control power up and power down of multiple power supplies (switchers or linear regulators). By staggering the startup sequence, it is possible to avoid latch conditions or large in-rush currents that can affect the reliability of the system. This is the figure of the circuit;

Available in a SOT23-6 package, the Power Sequencer contains a precision enable pin and three open drain output flags. Upon enabling the LM3880 the three output flags will sequentially release, after individual time delays, permitting the connected power supplies to startup. The output flags will follow a reverse sequence during power down to avoid latch conditions. EPROM capability allows every delay and sequence to be fully adjustable. Contact National Semiconductor if a non-standard configuration is required.

Linear Resistance Meter Circuit

2011-01-06T19:21:00.000+07:00

This is a one design circuit for analogue multi meters are capable of measuring resistance over quite a wide range of values, but are rather inconvenient in use due to the reverse reading scale which is also non-linear. This can also give poor accuracy due to cramping of the scale that occurs at the high value end of each range. This is the figure of the circuit;

This resistance meter has 5 ranges and it has a forward reading linear scale on each range. The full-scale values of the 5 ranges are 1K, 10K, 100K, 1M &10M respectively and the unit is therefore capable of reasonably accurate measurements from a few tens of ohms to ten Mega ohms. Most linear scale resistance meters including the present design, work on the principle that if a resistance is fed from a constant current source the voltage developed across that resistance is proportional to its value. For example, if a 1K resistor is fed from a 1 mA current source from Ohm’s Law it can be calculated that 1 volt will be developed across the resistor (1000 Ohms divided by 0.001 amps = 1 volt). Using the same current and resistance values of 100 ohms and 10K gives voltages of 0.1volts (100 ohms / 0.001amps = 0.1volts) and 10 volts (10000 ohms / 0.001amps = 10 volts). Thus the voltage developed across the resistor is indeed proportional to its value, and a voltmeter used to measure this voltage can in fact be calibrated in resistance, and will have the desired forward reading linear scale. One slight complication is that the voltmeter must not take a significant current or this will alter the current fed to the test resistor and impair linearity. It is therefore necessary to use a high impedance voltmeter circuit.

Electromagnetic Field Probe Circuit Using Meter Output

2011-01-06T19:19:00.000+07:00

This circuit is designed to locate stray electromagnetic (EM) fields. It will easily detect both audio and RF signals up to frequencies of around 100kHz. Note, however that this circuit is NOT a metal detector, but will detect metal wiring if it conducting ac current. This is the figure of the circuit;

Frequency response is from 50Hz to about 100kHz gain being rolled off by the 150p capacitor, the gain of the op-amp and input capacitance of the probe cable. Stereo headphones may be used to monitor audio frequencies at the socket, SK1. The output signal from the op-amp is an ac voltage at the frequency of the electro-magnetic field. This voltage is further amplified by the BC109C transistor, before being full wave rectified and fed to the meter circuit. The meter is a small dc panel meter with a FSD of 250uA. Rectification takes place via the diodes, meter and capacitor. Switch on, plug in headphones (optional) and move the probe around. Any electrical equipment should produce a hum and indicate on the meter. It remember once building a high gain preamp (for audio use). I made a power supply in the same enclosure. The preamp worked, but suffered from an awful mains hum. This was not directly from ripple on the power supply as it was regulated and well smoothed. What I had done was built the audio circuit on a small piece of veroboard, and placed it within a distance that was less than the diameter of the transformer.

3A Simple Switcher Power Module Using 20V Maximum Input Voltage

2011-01-06T19:16:00.000+07:00

This is a design circuit for power module that is an easy-to-use step-down DC-DC solution capable of driving up to 3A load with exceptional power conversion efficiency, line and load regulation, and output accuracy. The LMZ12003 is available in an innovative package that enhances thermal performance and allows for hand or machine soldering. This is the figure of the circuit;

The LMZ12003 can accept an input voltage rail between 4.5V and 20V and deliver an adjustable and highly accurate output voltage as low as 0.8V. The LMZ12003 only requires three external resistors and four external capacitors to complete the power solution. The LMZ12003 is a reliable and robust design with the following protection features: thermal shutdown, input under-voltage lockout, output over-voltage protection, short-circuit protection, output current limit, and allows startup into a pre-biased output. A single resistor adjusts the switching frequency up to 1 MHz.

YPBPR to RGB Video Converter Circuit Using LT6552

2010-12-21T12:49:00.000+07:00

This is a design circuit for LT6552 amplifiers connected to convert component video (YPBPR) to RGB. This is the figure of the circuit;

The LT6552 is a video difference amplifier optimized for low voltage single supply operation. The LT6552 features 75MHz – 3dB bandwidth, 600V/µs slew rate, and ±70mA output current making it ideal for driving cables directly. This circuit maps the sync on Y to all three outputs, so if a separate sync connection is needed by the destination device.

Magnetic Reed Switch Alarm Circuit

2010-12-21T12:45:00.000+07:00

This circuit is kind for made to be an alarm, both for home and handbags. If it is installed for home it will placed on door or windows, and if it is installed for bags or handbags it will placed in the bag. This circuit consists of a small magnet and a reed switch. If the magnet looses its contact with the reed switch, SW1 opens, the circuit starts oscillating and the loudspeaker emits a loud alarm sound. So this circuit suitable for use as an anti-theft alarm. This is the figure of the circuit;

This circuit uses A complementary transistor-pair which is wired as a high efficiency oscillator, directly driving a small loudspeaker. Low part-count and 3V battery supply enable a very compact construction. The loudspeaker’s dimensions are limited only by the box that contain it. If the circuit is used as anti-bag-snatching, SW1 can be replaced by a 3.5mm mono Jack socket and the magnet by a 3.5mm. Do not supply this circuit with voltages exceeding 4.5V: it will not work and Q2 could be damaged.

Low Distortion Crystal Oscillator Circuit

2010-12-21T12:41:00.000+07:00

This is a design circuit for Low Distortion Crystal Oscillator circuit. This circuit generate a sine wave that has low phase noise and distortion. This circuit can be used to perform a crystal with less than 1mV dissipated in crystal. The crystal is used to filter the signal current. This is the figure of the circuit;

If the impedance loads is low, the JFET will drive the impedance. When the loads is about 50ohm, it will better if an emitter follower combined with a voltage step-down transformer or matching network for further buffering. The value of C3 determined the output voltage, if the lower output voltage is required, the C3′s value should be increased and decrease the value of C3 when the larger output voltage is needed. If overtone crystal is used, a choke should replace the 1K emitter resistor. This choke must be resonates with C2 at a frequency slightly above the fundamental frequency for third overtone crystals. When uses the high-Q overtone crystal, the value of C3 should be lower because the High-Q overtone crystals should be driven at much lower levels than fundamental crystals. Besides that, the output level should be set as low as possible. If the crystal’s rated power or current is known, the drive level can be measured. To measure drive level temporarily connect a 100 ohm across C3 and measure the signal level on the source of the FET. The crystal current is determined by V/100.

LASER Door Alarm Circuit

2010-12-21T12:37:00.000+07:00

This is a circuit for laser door alarm is based on the interruption of Laser beam. A low cost Laser pointer is used as the source of light beam. When somebody breaks the laser path, the alarm will be generated for few seconds. This is the figure of the circuit;

The laser door alarm circuit has two sections. The laser transmitter is a laser pointer readily available. It should be powered with 3 volt DC supply and fixed on one side of the door frame. The receiver has a Phototransistor at the front end. L14F1 NPN Darlington phototransistor is used as the laser sensor. IC1 is used as a voltage comparator with its inverting input tied to a potential divider R2-R3. So that the inverting input is kept at half supply voltage. As a result, output of comparator remains low. LED and Buzzer remain off in this state. When a person crosses the door, laser beam breaks and T1 cease to conduct. Collector voltage of T1 rises and voltage at pin 3 of comparator increases and its output becomes high. This activates LED and buzzer. Capacitor C1 keeps the base of T2 high for few seconds even after the output of IC1 becomes low again. C2 gives current to the buzzer for few seconds even after T2 turns off.

Single Chip Stereo FM Transmitter Circuit

2010-11-20T11:30:00.000+07:00

ROHM (www.rohm.com) is originally a resistor producer company, but finally expand their business and produce monolithic IC, and this one used in our circuit is the example. The internal structure of this FM transmitter integrated circuit consist of stereo modulator that creates a stereo composite signal, an FM modulator that modulate a carrier frequency with the composite signal, and an RF amplifier that provide enough power to be transmitted through antenna. This is the figure of the FM transmitter circuit;

The core of this stereo FM transmitter is BA1404 integrated circuit chip. from ROHM. This FM transmitter is ideal for wireless microphone, or for audio interface and distribution for home or car appliance. For example, you can now play your portable mp3/mp4 player on your old car radio sound system that doesn’t have line-input plug. This stereo FM transmitter chip is designed for 75-108 FM band, and you can adjust the operation by trimming the LC network connected to pin 10 of this IC chip. To ease the adjustment, you can use a 22-33p variable capacitor for the 15p capacitor connected to pin 10. Finally, this stereo FM transmitter works with only 1.5-3V power supply, ideal for battery operation. More than 3.5V supply voltage could burn this FM transmitter circuit. [Circuit diagram source: ROHM Application Notes]

Buffering TMP01 Temperature Sensor Circuit

2010-11-20T11:26:00.000+07:00

This is a circuit for a buffer circuit for TMP01 Temperature Sensor. The output of this sensor is a low impedance dc output voltage with a 5 mV/K temperature coefficient. This sensor can be used in multiple control and measurement applications. The buffered VPTAT voltage output can drive 500 µA into 50 pF (maximum). This is the figure of the circuit;

To minimize loading that could create dissipation-induced temperature sensing errors and to ensure accuracy, an external amplifier is used in this circuit. The circuit can drive over 10 mA. It still stable under capacitive loads of up to 0.1 µF. [Circuit diagram source: analog.com]

Analog PID Controller

2010-11-20T11:20:00.000+07:00

This circuit is shows us about a form of PID controller. The input signal is buffered and amplified by a non-inverting amplifier and the gain of this stage defines the proportional gain P of the controller. The amplified error signal passes in parallel through an integrator (top) a unity-gain amplifier (middle) and a differentiator (bottom) all of which have inverting behaviour. The final op-amp sum and invert the outputs and passed to the output. The potentiometers labeled D and I control the proportions in which derivative and integral fractions contribute to the output signal which is proportional to the power W to be supplied to the heater. This is the figure of the circuit;

It is most likely to be troublesome by causing an offset between the set-point and oven temperatures. Under some circumstances the integrator may drift and eventually saturate which would prevent it from working properly. To reduce the impact of op-amp offset and bias, the first thing to try would be a resistor, equal in value to R2, between the positive input of the integrating op-amp and ground to eliminate the common-mode bias current. Selecting an op-amp with a good input-offset performance would be the next step.

TL084 Audio Compressor (AGC) Circuit

2010-11-01T09:48:00.000+07:00

Compressor or AGC (automatic gain control) is used to manipulate the average amplitude of audio signal, to produce relatively constant volume of signal from high dynamic signal source. The 2N3819 JFET (which is used as a voltage controlled resistor) is the key component. Control voltage which is derived by full-wave rectification followed by a peak detector is provided by the output of the circuit. The full wave rectifier is called a precision absolute value circuit can be found in Tobey, Graeme and Huelsman’s : “Operational Amplifier” (1971)- page 249. Several matched resistor is required by the circuit for correct operation and alternative versions of this sub-circuit, which require fewer matched resistors and overall fewer components, could be advantageously substituted. This is the figure of the design circuit;

The product of R4 and the 4.7 uF capacitor is determine the attack time. It’s becomes reverse biased when the input signal drops D1 and the decay time constant is determined by R5. (Since the original publication date I have discovered that the term ‘release’ is used rather than ‘decay’ in the case of compressors.) Both time constants are something of a compromise, the decay must be fast enough to allow low amplitude signals shortly following high amplitude ones to be given sufficient gain and the attack must be fast if the start of high amplitude signals are not to be overloaded until the gain reduces. After long periods of silence or low amplitude inputs, the problem occurs. The next high amplitude signal will get the ‘full gain treatment’ and so will initially overload the circuit and some distortion will be result. Reduce R4 to zero resulting in minimal attack time (determined by the maximum output current of IC3) is the best that could be done under these circumstance. The circuit is by no means ‘hi-fi’ but will be useful for AGC in tape-recording, radio and signal processing where a signal’s large dynamic range needs to be reduced. The original circuit uses 741 IC for the op-amps and OA81 for the diodes (D1,D2,D3).

Single Transistor Blocking Monostable Circuit

2010-11-01T09:45:00.000+07:00

This is a design circuit of blocking monostable circuit. The normal state of the transistor is off because the 10 k resistor has been removed. The conduction will be started using a positive pulse at node “a” and the transformer will do the rest. The transistor will again be turned off (by a hefty negative pulse to the base) after the brief excursion of conduction, in which the output falls to near ground. This is the figure of the circuit;

The trigger pulses are provided by an RC differentiating circuit in this circuit, which produces narrow pulses, alternately positive and negative. The positive pulses which need only be about 1V high is the only monostable responds. The circuit will produce one low-going pulse of brief duration. The pulses will be a normal string of positive pulses if the circuit is followed by a phase inverter. There is no effort has been made to make the pulses as short as possible. These will be 100-200 us wide.

SCR And Triac Triggering Circuit With A Positive Power Supply Circuit

2010-11-01T09:44:00.000+07:00

The control-circuit output current has to be amplified when the gate current required to trigger the device is higher than the control-circuit output current capability. For example, A lot of MCUs feature output pins with a current capability around 30 mA today. With IGT, they can switch Triacs safely up to 15 to 20 mA. Below are two solution if a Triac with a 35 or 50 mA IGT has to be controlled by such an MCU. First, Use several MCU output pins in parallel (the best is to use a separate gate resistor between each output pin and the Triac gate to ensure a good current repartition between each pin).

With the bipolar solution, the only way is use a PNP transistor to keep the current sourced to the gate. To set its drive reference to a stable bias, a PNP transistor has to be used, which is the power supply (Vdd) in this case. This is another drawback of the positive power supply topology. A PNP transistor has to be used instead of an NPN transistor to amplify the control circuit output current. Than an NPN, a PNP transistor has a lower current gain and higher price. [Circuit diagram source: STMicroelectronics Notes]

LM2576 Switching Regulator Circuit

2010-11-01T09:43:00.000+07:00

This is a design circuit that can be to produce any output voltage, an external feedback resistors can be added. The sLM2576 is a Switching Regulator that can produce 15, 12, 5, 0r 3.3V output voltage from maximum supply voltage of 60V or 40V. This LM2476 featured with voltage reference, switch and feedback path for use in either the negative boost or the buck saturation voltage of The LM2576 switch is typically 1.4V. A heatsink may be needed to solve the power dissipation, however the thermal dissipation is internally limited. The LM2576 has quiescent current of 50 µA in standby (on/off high). This circuit is a testing circuit for LM2576. This is the figure of the circuit;

The electrolytic capacitors at output and input should be connected with leads as close as possible. The power dissipation must be small because the load is 100R, so the heat sink is not needed. The capacitor’s voltage must higher than the voltages used in the experiment. This circuit uses 40V, 1A Schottky diode or the 40V, 3A 1N5822 for heavier currents.

Basic Uninterruptible Power Supply Circuit

2010-11-01T09:41:00.000+07:00

This is a design circuit for basic interruptible Power Supply Circuit consist of regular power supply adapter and battery connection. This basic system is a “hot” battery connection, meaning that there is no switching mechanism in connecting and disconnecting the battery, the battery is always connected! This hot connection is very simple to implement and very robust because there would be no switching delay, the output voltage will be 100% continue if a power down happens, until the battery loose its capacity. This is the figure of the circuit;

When the power line is normal, the current from the main adapter (transformer-rectifier diode bridge-filter capacitor) flow to the load through D3, and the battery is charged via R1 and D1. The diode D2 prevent the current at D3 output to be shorted by the empty battery in the normal power line condition. If the power down happens then the battery will supply the current to the load through D 2. Use a 15V AC output transformer for 12 volt lead acid battery. LED1 will indicate if the power line is normal. LED D1 will turn off if the power line is down.

UJT Relaxation Oscillator with Op-Amp Squarer

2010-10-23T01:32:00.001+07:00

The UJT below is configured to produce a sawtooth wave at a frequency of 104 Hz. The capacitor begins to charge through the 4.7 kOhm resistor when the circuit is initially powered up. The current suddenly flows from the UJT emitter (E) to the UJT Base (B1) when the voltage across the capacitor rises to a certain point. This will produce a voltage across the 100 ohm resistor which is the same as the output of the UJT relaxation oscillator on the Emitter. This is the figure of the circuit;

The sawtooth waveform is applied to op amp pin 3 and the voltage divider is applied to op amp 2. The op amp produces a positive going output on [in 6 when the sawtooth is higher than the reference from the divider of 2.5 volts. The op amp acts as a comparator. [Circuit's schematic diagram source: Chuck Bolin Electronic Project].

Passive Baxandall Tone Control (2 Band Equalizer)

2010-10-23T01:31:00.003+07:00

Variation of the famous Baxandall circuit is shown in the passive circuit in figure 1. Smoothly increasing +- 6 dB/octave slope of boost or cut is the feature of this circuit. Although the “shelves” are outside the audible range with these component values, the bass and treble filters have a shelving response. The threshold and shelving frequencies is predicted by the filter equations in figure 1a.The wiper shorts out the .033uf capacitor, when the bass control is rotated for maximum boost. A frequency dependent voltage divider that determines the shelf frequency of the boost are formed by R3 and C4. The wiper bypasses the 10K resistor. C1 and R2 form a high pass filter, when the treble control is set for maximum boost. This is the figure of the circuit;

The circuit uses commonly available parts to simplicity. Radio Shack sold even the 100k log taper pots, which are usually hard to find, as part number 271-1732 (in a stacked configuration for stereo). The pot will have about 10K on one side and 90K on the other at the midway point.The side with 10K parallels R2 for the treble control. The side with 10K parallels C4 for the bass control. Note that this circuit could be divided for an individual bass or treble control (R5 may then be omitted – it helps isolate the bass from the treble circuit when the two are put together). To avoid loading the network and affecting the response curves, the passive Baxandall must see a low impedance source and drive a high impedance load.

Op Amp Voltage Regulator Circuit

2010-10-23T01:30:00.002+07:00

This is a simple voltage regulator circuit that employs an operational amplifier (op-amp). As its name implies, this circuit accepts an unregulated voltage input (i.e., a fluctuating input voltage), and provides a regulated voltage output (a stable output voltage that remains at or very close to its intended output level). The unregulated input voltage must be higher than the desired output level by a sufficient margin in order to achieve 'effective' regulation. This is the figure f the circuit;

The zener diode Vz acts as a voltage reference for the circuit, and is fed into the non-inverting input of the operational amplifier. The voltage divider formed by R1 and RF sets the voltage level of the inverting input of the op amp, which is basically a feedback from the circuit output to the op amp. The NPN transistor is used to boost the output current of the circuit. The voltage at the non-inverting input of the op amp is pegged at the zener voltage, while the voltage at the inverting input is always a fraction of the output voltage as defined by RF and R1. When the output exceeds the set level, the inverting input voltage exceeds that of the non-inverting input, causing the output of the op-amp to go 'low'. This turns off the NPN transistor, causing the output voltage to dip. When the output goes below the set level, the reverse happens, i.e., the op-amp's output goes 'high', causing the NPN transistor to turn on and pull the voltage up.

Thus, this circuit works by turning off the transistor when the output voltage is too high and turning it on when the output is too low. This balancing act happens continuously, with the circuit reacting instantaneously to deviations in the output voltage. Resistor RF is adjusted to set the desired output voltage of the circuit. The zener diode needs to be replaced by a voltage reference IC if a more stable and more precise output is required.

OP90 4 mA to 20 mA Current Loop Transmitter Circuit

2010-10-23T01:29:00.002+07:00

This is a circuit for current loop circuit. An output of 4 mA to 20 mA that is linearly proportional to the input voltage is provided by the current transmitter on figure below. Line rejection is 0.0005%/volt and linearity of the transmitter exceeds 0.004%. This is the figure of the circuit;

The REF-02EZ provides biasing for the current transmitter. The output current is regulated by OP90EZ to satisfy the current summation at the noninverting node:

Iout = 1/R6((Vin.R5)/R2 + (5V.R5)/R1)

Iout = (16/100 ohm)Vin + 4mA

That’s will give a full-scale output of 20 mA with a 100mV input. By adjusting R2, we can provide a offset trim and adjustment of R1 will provide a gain trim. Since the non-inverting input of the OP90 is at virtual ground, these trims do not interact. The input voltage spike will be prevented by D1 (the Schottky diode) from pulling the non-inverting input more than 300 mV below the inverting input. Without diode, such spikes could cause phase reversal of the OP90 and possible latch-up of the transmitter. This circuit has compliance from 10V to 40V. For transducer excitation, the voltage reference output can provide up to 2 mA. [Circuit diagram source: Analog Application Note]

Enabling 3 Phase Motor to Operates with Single Phase Supply

2010-10-23T01:28:00.001+07:00

The capacitor has been use for decades to operate 3-phase motors on single-phase power. Two single-phase wires are connected to two of the inputs on a 3 phase motor on this method. Then, the capacitor is connected to one of the single -phase inputs and the third leg of the motor. This is the figure of the circuit;

The voltage is allowed to be displaced in time from its parent voltage by phase shift through the capacitor. Voltage distinct from the 2 single-phase lines is the result. The motor will operate if the capacitors value-it’s ability to process electrical current- is sufficient. 6 times as much current to start as it does to run is required by the motor so a static-capacitor phase converter must have some means of switching a large group of capacitors in and out during motor starting. Below is a typical unit uses a potential-type motor starting relay (pirated from a single-phase motor) to regulate the larger start capacitor, while a smaller (in value) capacitor provides continuous power to run the motor. The potential relay removes the start capacitor from the circuit as the motor speed increase, and the motor operates.

BTL Mono Amplifier with DC Volume Control Circuit

2010-10-23T01:26:00.002+07:00

This is the circuit for BTL (bridged tied load) mono amplifier with DC volume Control circuit. This circuit uses TDA7052A/AT that is suitable not only for monitors and TV but also battery fed portable radios and recorders. The difference between conventional DC volume circuits and TDA7052A/AT the DC volume control is there is no coupling capacitor is needed in TDA7052A/AT the DC volume control to maintain the low offset voltage. This is the figure of the circuit;

Besides that, the TDA7052A/AT the DC volume control requires low supply. The advantages of BTL principle are it has the ripple’s frequency on the supply voltage is twice the signal frequency and the supply current peak is lower. To save the cost, a smaller capacitor can be used. The BTL principle can be implemented in portable application that will decrease supply voltage but increases the output power. This amplifier has maximum gain of 35.5 dB. The mute mode is when the DC volume control voltage is below 0.3V. This circuit also equipped with thermal protection. The gain will be decreased when temperature reach +150 C. [Circuit's schematic diagram source: nxp.com]

Analog Tremolo (Guitar) Sound Effect Circuit

2010-10-23T01:25:00.002+07:00

This is the circuit for the tremolo effect produce an amplitude modulated signal. Unlike vibrato effect that produce frequency modulated, this tremolo effect will produce the same effect as quickly turning up-ad-down your volume control repeatedly. This is the figure of the circuit;

Q1 is general small signal audio transistor, you can use almost any type of NPN small signal transistors. MFC3304P is a voltage controlled amplifier IC with negative control, it might be difficult to find these days, but I think you can replace with general OTA (operational trans-conductance amplifier), with the appropriate biasing circuit off course. Just bias the current control of an OTA through a resistor, and add the C4 modulator signal at the control pin of the OTA.

Pink (Flicker) Noise Generator Circuit

2010-09-19T07:18:00.000+07:00

This is a circuit for a flicker noise generator, an implementation of flicker noise analog modeling presented in NBS technical note #604, “Efficient Numerical and Analog Modeling of Flicker Noise Processes” by J.A. Barnes and Stephen Jarvis, Jr. With the component values shown the schematic diagram, the circuit will give a 1/f noise slope from below 1Hz to over 4KHz. A TLC2272 op-amp is used for this circuit, but any low noise op-amps will work. This is the figure of the circuit;

The op-amp must be a low noise type because the noise generation comes from a high value resistor generating about 50nV noise. Use an op-amp with noise voltage less than 15 nV/root-Hz and noise current less than 0.1 pA/root-Hz, an easy-to-find feature in many low-noise modern op-amp devices. To simplify the construction, the capacitor values is slightly different from the calculated values described in the paper, and a bias circuit is provided to allow the use of polarized electrolytic capacitor. Because the electrolytic capacitor has poor tolerance, it should be chosen carefully for best performance. Compared to circuit utilizing diode zener, reverse-biased transistor, or other noisy devices, this circuit give more predictable and repeatable output level. If we tap the output of the first op-amp through a 100uF capacitor (like as seen in the second op-amp), a precise 5uV/root-Hz white noise will be there as an excellent signal source for audio noise measurement calibration. At the second op-amp, this white noise is filtered to give a flicker noise (pink noise) frequency spectrum, since the pink noise is a subset of white noise in the frequency domain.

Passive Treble Control Circuit for Guitar Pedal

2010-09-19T06:54:00.000+07:00

The R1/C1 network makes a low pass filter when the wiper is at the grounded end of the tone pot, and there is a treble cut. The C1 cap bypasses R2 when the wiper is adjusted so that it is at the top end of the pot and it creates a treble boost. This is the figure of the circuit;

The 100k output volume and the 100k tone pot are always in parallel as a constant load. It’s suggested to used a linear taper pot for the tone control and a log (audio) taper for the volume control. Suggested values for initial experimentation are R1=10k, R2=47k, and C1=0.022uF. Some signal loss, as with any passive network is the limitation of this combined tone control. However, many guitar pedal designs have strong enough output signal level, and this tone control is an excellent option for those circuits with enough drive.

Low Impedance Microphone Input Preamplifier Circuit

2010-09-19T06:43:00.000+07:00

This is a circuit for a low-impedance (Z = 50 to 200 ohms) microphone input circuit or pre-amplifier that employs low-cost, low-noise precision operational amplifiers such as the OP27 and the OP37. This is the figure of the circuit;

The simple circuit above amplifies differential signals from low-impedance microphones by 50 dB. Because of the high working gain of the circuit, use of the OP37 (which is a high-speed op amp) is recommended if bandwidth is important to the application. To ensure stability, a dummy resistor Rp must be placed between the OP37 inputs. This will prevent amplifier oscillation due to 100% feedback from the open input in case the microphone is unplugged.

IL300XC Isolation Amplifier Circuit for TMP01 Temperature Sensor

2010-09-19T06:29:00.000+07:00

This is a design circuit for about IL300XC Isolation Amplifier circuit for TMP01 Temperature Sensor. This circuit is used in an environment that needs to be electrically isolated from the central processing area. This circuit uses an 8-pin opto isolator (IL300XC). IL300XC was chosen because it can operate across a 5,000V. To drive the LED connected between Pin 2 and Pin 1, this circuit uses an OP290 single-supply amplifier. The photodiode connected from Pin 3 to Pin 4 gives the feedback. This is the figure of the circuit;

The OP290 drives the LED, that there is enough current generated in the photodiode to exactly equal the current derived from the VPTAT voltage across the 470 kO resistor. On the receiving end, the current from the second photodiode is converted to a voltage through its feedback resistor R2. TO buffer the 2.5 V reference voltage of the TMP01, this circuit uses the other amplifier in the dual OP290. It will give the an accurate, low drift LED bias level without affecting the programmed hysteresis current. The bias level accuracy at receiving end is provided by A REF43.

The current of the photodiode is determined by following equation:
I1=(2.5V-VPTAT)/470K
The output voltage is determined by following equation:
Vout=2.5V-I2*R2
=2.5V-0.7*((2,5V-VPTAT)/470)*644K=VPTATT

R2 must be larger than R1 to achieve overall unity gain because the gain of IL300XC is less than 1.0. To correct for the initial gain accuracy of the IL300XC, A trim is used in this circuit. Just adjust the trim to get output voltage equal to VPTAT at any particular temperature. Both the OP90 and REF43 contribute no significant error because of drift and operate from a single supply.

Frequency Divider Circuit

2010-09-19T06:14:00.000+07:00

This is a circuit for frequency divider circuit, or a circuit whose output frequency is a fraction of the frequency of its input. The main component of this circuit is the 555, a versatile timer IC. In this circuit, it is configured as a mono stable multi vibrator, i.e., it will output a single pulse at pin 3 every time its pin 2 is 'triggered' by a pulse. This is the figure of the circuit;

The width of the output pulse at pin 3 of the circuit above is defined by the product of R1 and C1, i.e., increasing the value of R1C1 will increase the output pulse width. Once the circuit above is triggered by a pulse at pin 2, the pin 3 output pulse cycle defined by R1C1 will first have to be completed before any subsequent pulses at pin 2 can trigger the circuit again. R1C1 of the circuit above can therefore be adjusted to define the number of input pulses equivalent to a single output pulse. Thus, this circuit is in effect dividing the input frequency by an integer.

Solar Charger Circuit

2010-09-14T22:30:00.000+07:00

This is a design circuit for a solar charger circuit to charge Lead Acid or Ni-Cd batteries using solar energy. The circuit harvests solar energy to charge a 6 volt 4.5 Ah rechargeable battery for various applications. The charger has Voltage and Current regulation and Over voltage cut off facilities. This is the figure of the circuit;

The circuit uses a 12 volt solar panel and a variable voltage regulator IC LM 317. The solar panel consists of solar cells each rated at 1.2 volts. 12 volt DC is available from the panel to charge the battery. Charging current passes through D1 to the voltage regulator IC LM 317. By adjusting its Adjust pin, output voltage and current can be regulated. VR is placed between the adjust pin and ground to provide an output voltage of 9 volts to the battery. Resistor R3 Restrict the charging current and diode D2 prevents discharge of current from the battery. Transistor T1 and Zener diode ZD act as a cut off switch when the battery is full. Normally T1 is off and battery gets charging current. When the terminal voltage of the battery rises above 6.8 volts, Zener conducts and provides base current to T1. It then turns on grounding the output of LM 317 to stop charging. [Circuit schematic source: D. Mohankumar Notes].

Op Amp Digital to Analog Converter Circuit

2010-09-14T22:27:00.000+07:00

This is a design circuit for a simple 4-bit digital-to-analog converter. It is actually just a simple op amp summer circuit, i.e., an operational amplifier configured to output a voltage that is proportional to the sum of the input voltages. This is the figure of the circuit;

The op-amp summer circuit above works as a DAC because its input voltages are binary weighted with respect to each other, as set by the resistors (10K, 20K, 40K, 80K) at the inputs.

The output Vo of this summer circuit w is:
Vo = -VRef (5K) (S3/10K + S2/20K + S1/40K + S0/80K) = -VRef (S3/2 + S2/4 + S1/8 + S0/16) wherein S3, S2, S1, and S0 are the logic inputs ('1' or '0'). The number of bits of this DAC may be increased by connecting more switches with corresponding binary-weighted resistors to the inputs.

Wheatston Bridge PWM Signal Conditioner Circuit

2010-09-05T21:59:00.000+07:00

This is a schematic diagram of a Wheatston Bridge PWM Signal Conditioner circuit. This circuit uses the MAX1452 signal conditioner. A ratiometric compensated output for the Wheatstone Bridge is generated by the MAX1452. Then the output of the Wheatston bridge is converted to a PWM output. the PWM-output duty cycle changes accordingly, as the MAX1452 output changes with pressure. the analog-output signal-conditioning ASICs can be used to substitute the MAX1452. This is the figure of the circuit;

Frequency counter with pulse-width-measurement option is the instrument that use the circuit. It need an accurate measurement of the PWM output’s pulse width. Beside that, a microcontroller can use the PWM output and the controller’s internal timer to calculate the time interval between high-to-low and low-to-high transitions. To calculate coefficients required to program the signal-conditioning IC, the measured PWM value can be used. [Circuit schematic source: MAXIM-IC.com]

AD586/597 Temperature Transducer (Sensor) Circuit

2010-09-05T21:56:00.000+07:00

This is a circuit for a stand alone temperature transducer/sensor circuit. This device uses The AD596/AD597, employing its internal junction compensation temperature sensor inside. This device can be used as temperature sensor by omitting the thermocouple and connecting the inputs (Pins 1 and 2) to common. This is the figure of the circuit;

The output will reflect the compensation voltage and the AD596/AD597 temperature will be indicated by the output. the AD596/AD597 will be operated over the full extended –55°C to +125°C temperature range. This device has output scaling of 10.1 mV per°C with the AD597 and 9.6 mV per °C with the AD596. when AD596 is used in temperature sensing mode, it will read slightly high, because there is 42mV offset.

DC Motor Reversing Circuit

2010-08-31T22:36:00.000+07:00

This is a design circuit for DC motor reversing circuit using non latching push button switches. Relays control forward, stop and reverse action, and the motor cannot be switched from forward to reverse unless the stop switch is pressed first. This is the figure of the circuit;

Assume that the motor is not running and that all relays are un-energized. When the forward button is pressed, a positive battery is applied via the NC contacts of B1 to the coil of relay RA/2. This will operate as the return path is via the NC contacts of D1. Relay RA/2 will operate. Contacts A1 maintain power to the relay even though the forward button is released. Contacts A2 apply power to the motor which will now run continuously in one direction. If now the reverse button is pressed, nothing happens because the positive supply for the switch is fed via the NC contact A1, which is now open because Relay RA/2 is energized. To Stop the motor the Stop switch is pressed, Relay D operates and its contact D1 breaks the power to relays A and B, (only Relay A is operated at the moment). If the reverse switch is now pressed and released. Relay B operates via NC contact A1 and NC contact D1. Contact B1 closes and maintains power so that the relay is now latched, even when the reverse switch is opened. Relay RC/2 will also be energized and latched. Contact B2 applies power to the motor but as contacts C1 and C2 have changed position, the motor will now run continuously in the opposite direction. Pressing the forward button has no effect as power to this switch is broken via the now open NC contact B1. If the stop button is now pressed. Relay D energizes, its contact D1 breaks power to relay B, which in turn breaks power to relay C via the NO contact of B1 and of course the motor will stop. All very easy. The capacitor across relay D is there to make sure that relay D will operate at least longer than the time relays A,B and C take to release.

Low Pass Filter Subwoofer Circuit Using TL062

2010-08-17T20:40:00.003+07:00

This is a circuit for subwoofer circuit. This circuit is simple design that is based on TL IC. This is the figure of the circuit;

In the form it appears the theoretical circuit of filter. In first glance we see three different circuits that are mainly manufactured round two operational amplifiers. This circuits constitute mixed, amplifier with variable aid and a variable filter. The manufacture end needs a circuit of catering with operational tendency of catering equal with ±12. the operational amplifiers that constitute the active elements for this circuits of are double operational type as the TL082 and NE5532. The operational these amplifiers belong in a family provided with transistor of effect of field IFET in their entries. Each member of family allocates in their circuit bipolar transistor and effect of field. This circuits can function in his high tendency, because that they use transistor of high tendency. Also they have high honor of rhythm of elevation (slew rate), low current of polarization for the entries and are influenced little by the temperature. The operational these amplifiers have breadth of area unity gain bandwidth 3MHz. A other important element for their choice is the big reject of noise, when this exists in the line of catering.

Low Impedance Microphone Amplifier Circuit

2010-08-17T20:39:00.000+07:00

This is a circuit for microphone amplifier for low impedance. This circuit is based on transistor for controller the circuit. This is the figure of the circuit;

This circuit is use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 6-30VDC. If you don't build the impedance adapter part with T1, you get a mic amp for higher impedance microphones. In this case, you should directly connect the signal to C7.

Part:
R1=15k
R2= 150k
R3= 2k2
R4= 820
R6= 10k
R7= 10k
P1= 1M
C1= 3k9
C2= 100u
C3= 22u
C4= 4u7
C5= 470u
C6= 10u
C7= 100n
C8= 47u UNIPOLAR
D1= 1N4148
U1= TL081
CN1= SIL6

Stabilizer Circuit

2010-08-15T07:00:00.000+07:00

This is a circuit for high quality power supply with a continuously variable stabilized output adjustable at any value between 0 and 30VDC. The circuit also incorporates an electronic output current limiter that effectively controls the output current from a few milliamperes (2 mA) to the maximum output of three amperes that the circuit can deliver. This is the figure of the circuit;

This feature makes this power supply indispensable in the experimenters laboratory as it is possible to limit the current to the typical maximum that a circuit under test may require, and power it up then, without any fear that it may be damaged if something goes wrong. There is also a visual indication that the current limiter is in operation so that you can see at a glance that your circuit is exceeding or not its preset limits.

Free Switch Mode Pre-Regulator Circuit

2010-08-15T06:58:00.000+07:00

This is a circuit for switch mode pre regulator circuit. The botheration was that a voltage regulator had to bead the 18 volt capital ability accumulation voltage to 8 volts at 500ma to ability the CD player, crumbling 5 watts of ability and causing a lot of calefaction central the bunched unit. This ambit acts as an interference-free pre-regulator to abundantly abate the ability loss. This is the figure of the circuit;

The achievement voltage of this ambit is artless by ability band fluctuations. Amount voltage aberration is alone abased on the on-resistance of Q2 and the amount of C2 (re: ripple). The achievement voltage can be set so that the ripple lulls are aloof aloft the drop-out voltage of the beeline regulator at best amount for best activity conservation. The college amount you aces for C2, the added activity you can save and the added abiding the pre-regulator’s achievement voltage.

FM Band Monaural Transmitter Circuit

2010-08-15T06:56:00.000+07:00

This is a circuit for a high quality monaural FM transmitter is quite useful in a variety of applications. The audio from a TV or entertainment system may be transmitted for remote or portable listening and for wireless earphone listening. This is the figure of the circuit;

The audio from an AM receiver placed near a window can be retransmitted within a metal building where AM reception is not possible. Two transmitters will convert two portable FM receivers into cordless stereo speakers for outdoor events. A keyboard may be played through the stereo without wires simply by tuning in the transmitter. A child will love an operational, miniature FM station complete with transmit "on the air" light. Simply connect the stereo's monaural output to the transmitter and transmit CDs, tapes, microphones, and other audio sources. Connect the transmitter to the computer's sound card and have big speaker sound. Even silence may be transmitted. Tune the transmitter to your favorite station and when the annoying commercial starts, simply flip on the power and silence.

Car Interior Light Extender Circuit

2010-08-15T06:54:00.000+07:00

This is a circuit for a Courtesy Light Extender for cars. When a door is closed in a car, it extends the ON time, so the passenger can see where he/she is sitting. This is the figure of the circuit;

The light normally goes off immediately when door switch is opened, but the circuit takes over and allows current to flow because the 22u is not charged and the first BC 547 transistor is not turned ON. To illuminate the interior light, this turns on the second BC547 via the 100k and the BD679 is also turned. The 22u gradually charges via the 1M and the first BC547 turns on, robbing the second BC547 of “turn-on” voltage and it starts to turn off the BD679. When the door is opened, the 1N4148 discharges the 22u.

20VAC 60 Watt Sunrise Lamp Circuit

2010-08-15T06:52:00.000+07:00

This is a circuit for a 120VAC lamp is slowly illuminated over a approximate 20 minute period. The bridge rectifier supplies 120 DC to the MOSFET and 60 watt lamp. A 6.2K, 5 watt resistor and zener diode is used to drop the voltage to 12 volts DC for the circuit power. The bridge rectifier should be rated at 200 volts and 5 amps or more. This is the figure of the circuit;

In operation, a 700 Hz triangle waveform is generated at pin 1 of the LM324 and a slow rising voltage is obtained at pin 8. These two signals are compared at pins 12 and 13 to produce a varying duty cycle rectangular waveform at pin 14, which controls the MOSFET and brightness of the 60 watt lamp. When power is applied, the lamp will start to illuminate within a minute or so, and will slowly brighten to full intensity in about 20 minutes. You can make that longer or shorter with adjustments to the 270K resistor at pin 9. The 2.2 ohm resistor and .015uF cap connected to the lamp serve to supress RFI. The diode at pin 9 and 10K resistor on pin 8 are used to discharge the 3300uF cap when power is removed. Power should be off for a few minutes before re-starting. This circuit is connected directly to the AC line and presents a hazard if any part is touched while connected to the line. Use caution and do not touch any parts while the circuit is connected to the AC line. You may want to use a 9 volt battery connected across the 12 volt zener to check the basic operation. The DC voltage at pins 1,2,3,5,6,7 will all be around 4.3 volts if the circuit is working correctly. If the DC voltages are all correct, you can use a variac to slowly apply the full line voltage and check for proper operation.

Voltage Doubler For Solar Battery Charger

2010-08-10T07:22:00.001+07:00

This is a circuit for PV Solar Panels have typical voltages of 3, 6, 12, 24 Volts. This circuit can be built which will increase the voltage output from a solar panel so it can be used to directly power a device or to charge batteries. This is the figure of the circuit;

It is comprised of some very easy to source components. The key component is the NE555 timer IC - one of the most popular integrated circuits (ICs) of all time. In this circuit it is used to generate short pulses of DC electricity which are passed through a couple of diodes and capacitors which act to multiply the voltage. The maximum output current of a 555 timer is typically 200 mA and it can dissipate up to 600mW of power. Exceed these specifications and the chip may be destroyed. Click here for full typical NE555 Specifications.

Timer Circuit Using 4060B IC

2010-08-10T07:21:00.001+07:00

This is a design circuit fir timer circuit that is based using 4060B. This is the figure of the circuit;

The pins labeled in red Q4-Q14 are the binary outputs: Q4 for the 16's, Q5 for the 32's, Q6 for the 64's and so on up to Q13 for the 8192's, and Q14 for the 16384's. Just three external components are required to control the 4060B counter - two resistors and one capacitor. The frequency of the internal oscillator (i.e. the speed of the count) is set according to the equation. Since Q14 represents the 16,384's and Q4 represents the 16's - we know it will take 1,024 times longer (16,384 / 16) for Q14 to flip from 0 to 1 than it takes Q4. So, for an example 2-hour timer (=7,200 seconds), we just need to fine-tune the circuit so that Q4 turns on after 7,200 / 1,024 seconds = 7.03 seconds, knowing that if that is done correctly, after exactly 2 hours Q14 will flip from 0 to 1.

500mW FM/VHF Transmitter Amplifier Circuit

2010-07-31T09:28:00.001+07:00

This is a circuit for power amplifier. This is the figure of the circuit;

This circuit is a high performance low noise 500mW amplifier / booster for all low power FM transmitters such as BA1404, BH1417, BH1415, 433MHz transmitter modules, etc. The amplifier chip is an integrated circuit containing multiple transistor stages and all other parts conveniently within a single small package. Boosting your FM transmitter has never been easier and the output signal can also directly drive 2n4427 or 2n3886 transistors for 1W or 5W of RF output power.

10W Power Amplifier Using TDA2003 IC’s

2010-07-31T09:24:00.001+07:00

This is a design circuit for power amplifier that is the circuit diagram of a 10W audio amplifier using the popular TDA2003 IC from SGS Thomson. This is the figure of the circuit;

The IC can easily deliver 10W to a 4 Ohms load at 18V DC supply voltage. The IC can be also operated from 12V and that makes it applicable in car audio systems. The useful features of TDA2003 includes short circuit protection between all pins, thermal overload protection, low harmonic distortion, low cross over distortion etc.

Random Blinking LED Circuit

2010-07-23T06:47:00.002+07:00

This is a design circuit to make the LEDs blink in a random pattern according to the slight differences in the three Schmitt Trigger oscillators. This is the figure of the circuit;

The CD4511 is BCD to 7 segment Driver, so the pattern of the led is actually the come from seven segment representation. Arrange the LEDs to be far from seven segment pattern if you want to avoid people analyze your circuit. The randomness is based on the frequency difference because the 22uF and 47k resistors that determine the frequency have at least 5% tolerance.

LED VU Meter Circuit Using LM3915 IC

2010-07-23T06:41:00.003+07:00

This LED VU Meter (volume-unit) is capable of monitoring and displaying power levels present at the speaker terminals of an stereo audio power amplifier. The levels are displayed in ten discrete steps using 10 LEDs for each channel. This project is designed to give an approximate visual indication of the audio power output of each channel. This is the figure of the circuit;

Two external resistors (R2 & R3) programs the full scale from between 1.2V and 12V applied to pin 5. 10.5V is used to turn on all 10 LED's. The voltage required to turn on all the LEDs is set by R2 and R3. The IC develops a nominal 1.25V reference voltage (Vref) across pins 7 and 8. Since this voltage is constant then the current through R3 is also constant. This current also flows through R2. The total voltage across R2 and R3 is given by voltage. Internally this chip consists of ten voltage comparators. The non-inverting (+) input of each comparator is connected to an accurate ten-step voltage divider network. Each comparator will therefore trigger on a different comparison level. The inverting (-) inputs of each comparator are commoned together and connected to an incoming DC signal via a high impedance input buffer.

Light Dependent Resistor Circuit

2010-07-19T13:20:00.002+07:00

The Light Dependent Resistor and a trimpot form a voltage divider which is used to apply bias to a transistor. As the LDR changes resistance the change in potential is detected by the circuit and the relay is activated. The PCB-mounted switch just interchanges the trimpot & the LDR as far as the detection circuit is concerned. So a dark activated switch becomes a light activated switch or vice versa. This is the figure of the circuit;

An LED with current limiting resistor is in parallel to the relay to give a visual indication of when the relay is turned on. The relay (Use a 5A/250VAC) can be connected to a light bulb and power supply which will light up when the environment is bright or vice versa. This circuit is satisfactory if the changes in light level to be detected are large and the transition is quick - for example, a person walking past a doorway. An inherent problem of the circuit is chattering of the relay for slowly changing light levels just at the transition point between turning on/odd and vice versa. This leads to the relay chattering as it rapidly turns on/off. This problem can be overcome in by having a hysteresis circuit using an op-amp or a Schmidt Trigger.

3V FM Transmitter Circuit

2010-07-19T13:15:00.002+07:00

This is a design of circuit and the parts list needed to built a 3V FM Transmitter. This FM transmitter is about the simplest and most basic transmitter to build and have a useful transmitting range. It is surprisingly powerful despite its small component count and 3V operating voltage. It will easily penetrate over three floors of an apartment building and go over 300 meters in the open air. This is the figure of the circuit;

The circuit is basically a radio frequency (RF) oscillator that operates around 100 MHz. Audio picked up and amplified by the electret microphone is fed into the audio amplifier stage built around the first transistor. Output from the collector is fed into the base of the second transistor where it modulates the resonant frequency of the tank circuit (the 5 turn coil and the trimcap) by varying the junction capacitance of the transistor. Junction capacitance is a function of the potential difference applied to the base of the transistor. The tank circuit is connected in a Colpitts oscillator circuit. Components may be added to the PCB in any order. Note that the electret microphone should be inserted with the pin connected to the metal case connected to the negative rail (that is, to the ground or zero voltage side of the circuit). The coil should be about 3mm in diameter and 5 turns. The wire is tinned copper wire, 0.61 mm in diameter. After the coil in soldered into place spread the coils apart about 0.5 to 1mm so that they are not touching. (The spacing in not critical since tuning of the Tx will be done by the trim capacitor. It is quite possible, but not as convenient, to use a fixed value capacitor in place of the trim capacitor - say 47pF - and to vary the Tx frequency by simply adjusting the spacing of the coils. That is by varying L of the LC circuit rather than C.) Adding and removing the batteries acts as a switch. Connect a half or quarter wavelength antenna (length of wire) to the aerial point. At an FM frequency of 100 MHz these lengths are 150 cm and 75 cm respectively.

Small Amplifier Circuit Using Transistors

2010-07-13T07:29:00.001+07:00

This is a design circuit for audio amplifier circuit. When audio is detected, the output is push-pull and consumes less than 3mA (with no signal) but drives the earpiece to a very loud level. It’s extremely difficult to set up because the whole circuit is DC coupled. Basically you don’t know where to start with the biasing. 8k2 between the emitter of the first transistor and 0v rail and the 470R resistor are the two most critical components. This is the figure of the circuit;

The emitter voltage on the BC 547 is set by the 8k2 across the 47u and this turns it on. To call the driver transistor, the collector is directly connected to the base of a BC 557. Current flow through the 1k and 470R resistors so that the voltage developed across each resistor turns on the two output transistors is caused by these transistors and the output of BC 557 are now turned on. The end result is mid-rail voltage on the join of the two emitters. Major negative feedback is provided by 8k2 feedback resistors while the 330p prevents high-frequency oscillations occurring.

[Circuit diagram source: Talking Electronics]

Active Crossover Circuit: Split The Audio Signal Before Amplification

2010-07-13T07:28:00.002+07:00

You might be familiar with passive crossover network installed inside your speaker box, consist of inductors and capacitors. The problem with passive crossover network is that they dissipate the audio power, so it’s not environmentally friendly, contributing a little disaster of global warming. Moreover, the capacitor and the inductor in the passive crossover network contribute the distortion of the signal since it must drive a low impedance load (the loud speaker). The best way to get high quality audio is to separate the high and low frequencies before feeding the signal to the amplifier. The drawback is that you need two amplifiers, to amplify the low and high audio signal separately. This is the figure of the circuit;

The circuit use a constant voltage method, means that the output of high and low frequency is summed up, and then fed back to be compared with the input to make sure this sum is equal to the input signal. This method is ensures that the total response is flat, if we summed back the separated high and low frequency output. You have to use 1% tolerance for the resistors to give a precise response. According to the formula, the capacitor C should be 6.6nF to give 1kHz crossover frequency, but a 6.8nF can be used because it widely available, and the crossover frequency will be shifted to about 975Hz.

[Circuit schematic diagram source: National Semiconductor Application Notes]

USB Devices Charger Circuit

2010-06-21T18:11:00.002+07:00

If you are in the traveling, you may be need this device to charge your gadget along the way, since it is much cheaper to buy some standard AA batteries for backup than buying several rechargeable batteries of your gadget type. Below is a charger that more efficient than linear regulator like the “7805″ while you are on the go. The most important component on this device is the “LT1301″. This is a small step up converter for to build switching mode power supply with only a few external components. This is the figure of the circuit;

To build this device, you need a LT1301 and a ic socket (8DIP), 2 electrolyte caps WITH! low ESR (6,3V 100uF), one inductor with a very LOW! DCR (around 0,03R) with 10uH should be able to handle switching currents at about 1,5 Amperes, one schottky rectifier like “SB130″ or “1N5817″ (important if you can’t get one of the two proposed rectifiers: low forward voltage drop, fast switching capability and it should be able to handle currents of 1 Ampere.), and A switch(on/off), an USB connector, a circuit board, a LED with resistor (limit led current to 2mA!, don’t loose your mA by pumping them through the LED) and don’t forget the battery holder.

Servo Motor System Controller Circuit

2010-06-21T18:09:00.002+07:00

This is a design circuit for a Servo System Controller circuit. This circuit is used to control a servo motor remotely. This circuit uses the 555 and requires only six extra components. This is the figure of the circuit;

[Schematic circuit source: Philips Semiconductors Application Note]

Decibel Sound Pressure Level Meter Circuit

2010-06-21T18:07:00.002+07:00

This is a design for decibel meter circuit. This circuit is used to measure sound pressure level (SPL) from about 60 to 70 dB. In this circuit, the transistor stage and one LM324 op-amp section are used to amplify the sound that is picked up by an 8 ohm speaker. As voltage comparators, the circuit uses The remaining 3 sections of the LM324 quad op-amp. 3 indicator LEDs are driven by the LM324. This is the figure of the circuit;

This circuit uses 3 LEDs as indicators. Each LED represents about a 3dB change in sound level, so that when all 3 LEDs are on, the sound level is about 4 times greater than the level needed to light one LED. the 500K pot can be used to adjust the sensitivity of the circuit. One LED is used as a reference sound level. The other two LEDs is used to indicate about a 2X and 4X increase in volume.

Audio Amplifier Circuit with DC Volume Control

2010-06-21T18:03:00.001+07:00

This is a design circuit for audio power amplifier. This circuit uses based on TDA7052B. The TDA7052B and TDA7052BT are 0.5 W and 1 W mono Bridge-Tied Load (BTL) output amplifiers with DC volume control. Not only have been designed for use in TV and monitors, but TDA7052B and TDA7052BT are also suitable for use in battery-fed portable recorders and radios. This is the figure of the circuit;

This devices are integrated with a Missing Current Limiter (MCL). When the difference in current between the output terminal of each amplifier exceeds 100 mA (300 mA typ), the MCL circuit is activated. Headphone application will be allowed on this 100mA level (single-ended).
[Circuit source: NXP Application Note]

Digital Step Km Counter Circuit

2010-06-07T18:54:00.001+07:00

This circuit is designed for measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. The rightmost display D1 (the least significant digit) shows hundred meters and its dot illuminates after every 50 meters of walking. A beeper (excludable), signals each count unit, occurring every two steps. This is the figure of the circuit;

This circuit has operation with based on 2 IC. IC1A & IC1B form a mono stable multi vibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divides by 64. Q2 drives the LED dot-segment of D1 every 32 pulses counted by IC2. Either IC3 & IC4 divide by 10 and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each mono stable count. Q1 drives the piezo sounder and SW2 allows to disabled the beep.

A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on. For low battery consumption the display illuminates only on request, pushing on P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together.

Part:

R1,R3____22K 1/4W Resistor

R2________2M2 1/4W Resistor

R4________1M 1/4W Resistor

R5,R7,R8__4K7 1/4W Resistor

R6_______47R 1/4W Resistor

R9________1K 1/4W Resistor

C1_______47nF 63V Polyester Capacitor

C2______100nF 63V Polyester Capacitor

C3_______10nF 63V Polyester Capacitor

C4_______10µF 25V Electrolytic Capacitor

D1_______Common-cathode 7-segment LED mini-display (Hundreds meters)

D2_______Common-cathode 7-segment LED mini-display (Kilometers)

IC1______4093 Quad 2 input Schmitt NAND Gate IC

IC2______4024 7 stage ripple counter IC

IC3,IC4__4026 Decade counter with decoded 7-segment display outputs IC

Q1,Q2___BC327 45V 800mA PNP Transistors

P1_______SPST Pushbutton (Reset)

P2_______SPST Pushbutton (Display)

SW1______SPST Mercury Switch, called also Tilt Switch

SW2______SPST Slider Switch (Sound on-off)

SW3______SPST Slider Switch (Power on-off)

BZ_______Piezo sounder

B1_______3V Battery (2 AA 1.5V Cells in series)

8 Channel Running Light Circuit

2010-06-07T18:45:00.002+07:00

This is a simple application that can be used for modern home. This circuit is used 2 IC. This circuit used 7475 quad latch IC. This is the figure of the 8 channel running light circuit;

This circuit can be used to bore unwanted guest, like pats, etc. LEDs are driven by the outputs of the four latches from the IC.

Servo Motor System Controller Circuit

2010-05-18T20:21:00.002+07:00

This is a design circuit for a Servo System Controller circuit. This circuit is used to control a servo motor remotely. This circuit uses the 555 and requires only six extra components.

This is the figure of the circuit;

[Schematic circuit source: Philips Semiconductors Application Note]

Audio Amplifier Circuit with DC Volume Control

2010-05-18T20:19:00.002+07:00

This devices are integrated with a Missing Current Limiter (MCL). When the difference in current between the output terminal of each amplifier exceeds 100 mA (300 mA typ), the MCL circuit is activated. Headphone application will be allowed on this 100mA level (single-ended).

[Circuit source: NXP Application Note]

Voltage to Pulse Duration Converter Circuit

2010-05-15T18:46:00.002+07:00

This is a design circuit for voltage to pulse duration converter. This circuit is control using op amp 741. This is the figure of the circuit;

This circuit is used to convert voltage into pulse duration by combining a timer IC and an OP Amp. This circuit can obtain accuracy up to better than 1%. The output signal is independent of the input voltage and still retain the original frequency.

[Circuit source: Philips Semiconductor Notes]

Salt Tester Circuit

2010-05-15T18:43:00.001+07:00

This circuit was designed to detect the approximate percentage of salt contained in a liquid. After careful setting it can be useful to persons needing a quick, rough indication of the salt content in liquid foods for diet purposes etc. This circuit is using LM324 as main components. This is the figure of the circuit;

IC1A op-amp is wired as a DC differential amplifier and its output voltage increases as the DC resistance measured across the probes decreases. In fact, fresh water has a relatively high DC resistance value that will decrease proportionally as an increasing amount of salt is added. IC1B, IC1C and IC1D are wired as comparators and drive D5, D4 and D3 in turn, as the voltage at their inverting inputs increases. Therefore, no LED will be on when the salt content of the liquid under test is very low, yellow LED D5 will illuminate when the salt content is low, green LED D4 will illuminate if the salt content is normal and red LED D3 will illuminate if the salt content is high. D1 and D2 are always on, as their purpose is to provide two reference voltages, thus improving circuit precision. At D2 anode a stable 3.2V supply feeds the non-inverting inputs of the comparators by means of the reference resistor chain R8, R9 and R10. The 1.6V reference voltage available at D1 anode feeds the probes and the set-up trimmer R4. One of these two red LEDs may be used as a pilot light to show when the device is on.

Parts:

R1________________470R 1/4W Resistor

R2,R5______________10K 1/4W Resistors

R3,R6_____________220K 1/4W Resistors

R4__________________5K 1/2W Trimmer Cermet

R7________________680R 1/4W Resistor

R8__________________2K2 1/4W Resistor

R9,R10,R11,R12,R13__1K 1/4W Resistors

C1________________100µF 25V Electrolytic Capacitor

D1,D2,D3______3 or 5mm. Red LEDs

D4____________3 or 5mm. Green LED

D5____________3 or 5mm. Yellow LED

IC1_______________LM324 Low Power Quad Op-amp

P1_________________SPST Pushbutton

Probes_________________ (See Text)

B1___________________9V PP3 Battery

Clip for PP3 Battery

Stereo Audio Coder-Decoder Circuit

2010-05-14T19:46:00.001+07:00

This is a design circuit for audio coder and decoder. This audio coder-decoder is suitable for home and portable applications like MD, CD and MP3 players. This circuit uses UDA1380 for main components. This is the figure of the circuit;

The UDA1380 is a stereo audio coder-decoder, available in TSSOP32 (UDA1380TT) and HVQFN32 (UDA1380HN) packages. All functions and features are identical for both package versions. The term ‘UDA1380’ in this document refers to both UDA1380TT and UDA1380HN, unless particularly specified. The front-end of the UDA1380 is equipped with a stereo line input, which has a PGA control, and a mono microphone input with an LNA and a VGA. The digital decimation filter is equipped with an AGC which can be used in case of voice-recording.

The DAC part is equipped with a stereo line output and a headphone driver output. The headphone driver is capable of driving a 16 W load. The headphone driver is also capable of driving a headphone without the need for external DC decoupling capacitors, since the headphone can be connected to a pin VREF (HP) on the chip.

[Circuit schematic diagram source: Phillips Semiconductor Notes]

High Efficiency Filter Circuit 3W Switching Audio Amplifier

2010-05-07T20:52:00.002+07:00

This is a design circuit for filter circuit for amplifier. This circuit is a simple design circuit that is based on LM4670. This is the figure of the circuit;

The LM4670 is designed to meet the demands of mobile phones and other portable communication devices. Operating on a single 5V supply, it is capable of driving a 4 speaker load at a continuous average output of 2.3W with less than 1% THD+N. Its flexible power supply requirements allow operation from 2.4V to 5.5V. The LM4670 has high efficiency with speaker loads compared to a typical Class AB amplifier. With a 3.6V supply driving an 8 speaker, the IC's efficiency for a 100mW power level is 77%, reaching 88% at 600mW output power. [Schematic circuit source: National Semiconductor Notes].

Boosted Class D Audio Power Amplifier Circuit

2010-05-07T20:50:00.001+07:00

This is a circuit of the power amplifier that is regulate by LM48510. This is a simple basic form circuit. This is the figure of the circuit;

The IC integrates a boost converter with a high efficiency mono, Class D audio power amplifier to provide 1.2W continuous power into an 8Ω speaker when operating on a 3.3V power supply with boost voltage (PV1) of 5.0V. When operating on a 3.3V power supply, the LM48510 is capable of driving a 4Ω speaker load at a continuous average output of 1.7W with less than 1% THD+N. The LM48510 is designed for use in mobile phones and other portable communication devices. The high (76%) efficiency extends battery life when compared to Boosted Class AB amplifiers. The LM48510 features a low-power consumption shutdown mode. Shutdown may be enabled by driving the Shutdown pin to a logic low (GND). The gain of the Class D is externally configurable which allows independent gain control from multiple sources by summing the signals. Output short circuit and Thermal shutdown protection prevent the device from damage during fault conditions. Superior click and pop suppression eliminates audible transients during power-up and shutdown.