Water Level Alert Circuit

This is a circuit that can be use when the water contained into a recipient has reached the desired level. This circuit is work with based on 555 timer IC. This is the figure of the circuit.


C1, a 555 CMos timer chip, is wired as an astable multi vibrator whose operating frequency is set by C1, R1 and R2, plus the resistance presented by water across the probes. If the resistance across the probes is zero (i.e. probes shorted), the output frequency will be about 3Hz and the sounder will beep (or the LED will flash) about three times per second. As water usually presents a certain amount of resistance, the actual oscillation frequency will be lower: less than one beep/flash per second. As probes will be increasingly immersed in water, the resistance across them will decrease and the oscillation frequency of IC1 will increase. This means that a rough aural or visual indication of the level reached by water will be available. If a LED is chosen as the alert, C2, D1 and D2 must be added to the circuit in order to double the output voltage, thus allowing proper LED operation (see the rightmost part of the schematics). Interesting features of this circuit are 1.5V supply and ultra-low current consumption: 40µA in stand-by and 0.5mA in operation. This allows a single AAA alkaline cell to last several years and the saving of the power on/off switch.

Part:
R1_______________1K 1/4W Resistor
R2_____________100K 1/4W Resistor (See Notes)
C1_______________2µ2 50V Electrolytic Capacitor
C2_____________220µF 25V Electrolytic Capacitor (See Notes)
D1______________5 or 10mm. Ultra-bright red LED (See Notes)
D2____________1N5819 40V 1A Schottky-barrier Diode (See Notes)
IC1_____________7555 or TS555CN CMos Timer IC
BZ1____________Piezo sounder (incorporating 3KHz oscillator)
B1_____________1.5V Battery (AAA or AA cell etc.)

PWM Motor DC using SG3525

This circuit is design for accurate control of DC motors. DC voltage conversion to a series of pulses, such that the duration of the pulse is a direct proportion to the value of DC voltage. Here’s the figure of the circuit.


This circuit protects against overload and short, PWM range can be adjusted 0-100%, PWM frequency of 100Hz-5KHZ adjusted. Operating voltage of 8 V ~ 35V, minimum current consumption is around 35mA. Maximum current can go to 6.5A. Efficiency better than 90% at full load. There are three trimpot potentiometer, where the function of three trim pots are as follows: VR1: adjust the minimum output voltage VR3: setting the maximum output voltage VR2: setting the output frequency.

Long Range FM Transmitter Circuit

This is a circuit for project the FM circuit. Transmitter circuit described here has the additional RF power amplifier stage, after the oscillator stage, to increase the power output of 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element antenna, this transmitter can provide a good enough signal strength to a distance of about 2 kilometers. Here’s the figure of the project circuit of the transmitter circuit.


The circuit built around transistor T1 (BF494) is the basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class power amplifier. This increases the oscillator signals’ power four to five times. Thus, 200-250 milliwatts of power produced at the collector of transistor T2. For better results, assemble the circuit on a good quality glass epoxy board and house the transmitter in the case of aluminum. Shield the oscillator stage using aluminum sheets. Transistor T2 must be mounted on the heat sink. Do not switch on the transmitter without a matching antenna. Adjust both trimmers (VC1 and VC2) for maximum transmission power. Adjust potentiometer VR1 to set the fundamental frequency near 100 MHz.

Audio Power Amplifier Circuit

This is a circuit for power amplifier and useful for audio. This circuit is work with based on transistor. Though the design is simple, these amplifiers have impressive performance, with a frequency response to approx 40 kHz, very low noise, reasonably fast slew rate, and approx 50 watts with the proper +/- 40 volt unregulated power supply. Here’s the figure of the circuit.

Amplified Ear Circuit

This is a project circuit is use for 32 Ohms impedance mini-earphones, can detect very remote sounds. This circuit is work with based on transistor. This is the figure of the circuit.


The heart of the circuit is a constant-volume control. All the signals picked-up by the microphone are amplified at a constant level of about 1 Volt peak to peak. In this manner very low amplitude audio signals are highly amplified and high amplitude ones are limited. This operation is accomplished by Q3, modifying the bias of Q1 (hence its AC gain) by means of R2. A noteworthy feature of this circuit is 1.5V battery operation.

Part:
P1_____________22K Log. Potentiometer (see Notes)
R1,R9__________10K 1/4W Resistors
R2______________1M 1/4W Resistor
R3______________4K7 1/4W Resistor
R4,R7_________100K 1/4W Resistor
R5______________3K9 1/4W Resistor
R6______________1K5 1/4W Resistor
R8_____________100R 1/4W Resistor
C1,C2_________100nF 63V Polyester or Ceramic Capacitors
C3,C6___________1΅F 63V Polyester or Ceramic Capacitors
C4_____________10΅F 25V Electrolytic Capacitor
C5____________470΅F 25V Electrolytic Capacitor
D1___________1N4148 75V 150mA Diode
Q1,Q2,Q3,_____BC547 45V 100mA NPN Transistors
Q4____________BC337 45V 800mA NPN Transistor
MIC1__________Miniature electret microphone
SW1____________SPST Switch (Ganged with P1)
J1_____________Stereo 3mm. Jack socket
B1_____________1.5V Battery (AA or AAA cell etc.)

Guitar Control

This circuit is design for a stand-alone portable unit, useful to control the signals generated by guitar pick-ups, particularly the contact "bug" types applied to acoustic instruments. This circuit is work with BIFET dual op amp. Here’s the schematic diagram of the guitar control


IC1A op-amp is wired as an inverting amplifier, having its gain set by a three ways switch inserting different value resistors in parallel to R4. This input stage is followed by an active three-band tone control stage having unity gain when controls are set in their center position and built around IC1B.

Part:
P1,P2_________100K Linear Potentiometers
P3____________470K Linear Potentiometer
P4_____________10K Log. Potentiometer

R1____________150K 1/4W Resistor
R2____________220K 1/4W Resistor
R3_____________56K 1/4W Resistor
R4____________470K 1/4W Resistor
R5,R6,R7_______12K 1/4W Resistors
R8,R9___________3K9 1/4W Resistors
R10,R11_________1K8 1/4W Resistors
R12,R13________22K 1/4W Resistors

C1____________220nF 63V Polyester Capacitor
C2,C8___________4µ7 63V Electrolytic Capacitors
C3_____________47nF 63V Polyester Capacitor
C4,C6___________4n7 63V Polyester Capacitors
C5_____________22nF 63V Polyester Capacitor
C7,C9_________100µF 25V Electrolytic Capacitors

IC1___________TL062 Low current BIFET Dual Op-Amp

J1,J2__________6.3mm. Mono Jack sockets

SW1______________1 pole 3 ways rotary or slider switch
SW2______________SPST Switch

B1_______________9V PP3 Battery

Adjustable Power Supply Using LM723

This is a design circuit for variable or adjustable power supply. This variable power supply is a simple but reliable one based on an integrated voltage regulator LM723. Here’s figure of the power supply circuit.


The R2 is set the output voltage. The maximum flow is determined by the value of R3, the excessive current in the circuit protection senses R3 and LM723 voltage output stage begins to close off this fast voltage approaches 0.65 V. In this way the current through R3 can never exceed 0.65/R3, even if output is shorted. C3 and C4, both ceramic, should be placed as close as possible to the integrated circuit, because the LM723 can be vulnerable to unwanted oscillations. The LM723 works with the input DC voltage V and IC 9,5-40 itself can be the source of about 150 mA if the output voltage is not more than 6-7 V below the input. When the external pass transistor is used (in the usual emitter-follower mode), the base-emitter of T1 is a significant resistance and the output stage of integrated circuits is relatively light load. All the current drawn by the load through a T1 and it decreases the amount of power that is proportional to the current and the difference between input and output DC voltage.

Source: www.zen22142.zen.co.uk

Rain Detector Circuit

This is a circuit for alarm that is sensing the water. This circuit is work with based on 555 astable multi vibrator that is used here which gives a tone of about 1kHz upon detecting water. Here’s the circuit diagram.


It has to placed making an angle of about 30 - 45 degrees to the ground. This makes the rain water to flow through it to the ground and prevents the alarm from going on due to the stored water on the sensor. The metal used to make the sensor has to be aluminum and not copper. This is because copper forms a blue oxide on its layer on prolonged exposure to moisture and has to be cleaned regularly. The aluminum foils may be secured to the wooden / plastic board via epoxy adhesive or small screws.

The contact X and Y from the sensor may be obtained by small crocodile clips or you may use screws.

Magnetic Radiation Remote Control

This circuit is useful as a short-range, single-channel remote-control. This circuit is work based on a non-modulated 35KHz frequency carrier transmitter, and on a high-gain two-stage 35KHz amplifier receiver, followed by a frequency-voltage converter and DC load driver. This is the figure of the circuit.


This circuit is consists of two part, transmitter and receiver. In the transmitter, Q1 and Q2 are wired as a Darlington pair to obtain the highest possible output from a Hartley type oscillator. C2 must be trimmed to obtain the highest sine wave output (best viewed on oscilloscope). In the prototype the sine wave amplitude measured across C1 leads reached 800V peak-to-peak at 9V supply and 450mA current.

In the receiver circuit, Q1 and Q2 form a two-stage linear amplifier. Therefore, the small 35 KHz signal picked-up by L1 is highly amplified by these devices and feds Q3 wired as a pulse-to-DC converter. When the input signal reaches Q3, the collector voltage of this transistor goes low, thus activating the LED D1 (or the optional beeper or relay) by means of Q4. Stand-by current is only 100µA. Current drawing is about 10mA when the LED is on and about 20mA when a relay is activated.

Transmitter parts:
R1_____________68K 1/4W Resistor
C1______________4n7 630V Ceramic or Polyester Capacitor
C2__________60-80pF 63V Ceramic Trimmer
C3____________100µF 25V Electrolytic Capacitor
Q1____________BC337 45V 800mA NPN Transistor
Q2____________BD139 80V 1.5A NPN Transistor
L1_________________ 500 turns on a 10mm. diameter, 10cm. long ferrite rod.
Enameled wire diameter: 0.2mm.
The tap is made after 200 turns, ground side
P1_____________SPST Pushbutton
B1_____________6-9V Battery

Receiver parts:
R1,R3___________1M 1/4W Resistors
R2,R4__________47K 1/4W Resistors
R5____________330K 1/4W Resistor
R6,R7__________68K 1/4W Resistors
R8____________180R 1/4W Resistor
R9____________100R 1/4W Resistor
C1____________470pF 63V Ceramic Capacitor (See Notes)
C2_____________10nF 63V Polyester or Ceramic Capacitor
C3____________100µF 25V Electrolytic Capacitor
C4,C5_________100nF 63V Polyester or Ceramic Capacitors
C6______________1µF 63V Polyester, Ceramic or Electrolytic Capacitor
D1_____________5 or 3mm. Red LED
Q1,Q2,Q3______BC549C 25V 100mA NPN High-gain Low-noise Transistors
Q4____________BC328 30V 800mA PNP Transistor
L1_________________ 700 turns on a 10mm. diameter, 10cm. long ferrite rod.
Enameled wire diameter: 0.2mm.
The tap is made after 350 turns, i.e. at the center
of the winding
BZ1___________Piezo sounder (incorporating 3KHz oscillator, optional, see Notes)
RL1______________5V DIL Reed-Relay SPDT or DPDT (Optional, see Notes)
B1_______________3V Battery (2 x 1.5V AA, AAA or AAAA Cells in series
or 1 x 3V Lithium Cell)

15dB UHF TV Antenna Booster Circuit

This is a circuit for antenna UHF TV that can be give 15dB preamp. This circuit is built by transistor and low components. This is the figure of the circuit.


The circuit above is formed based on BF180 UHF Transistor. The first stage is a band pass filter constructed by the C1, CV1, L1, L4, C7 and C3, the second stage is a base-common voltage amplifier with low input impedance to match. Build the L1 ~ L4 as air core coil to obtain high Q-Factor. After assembling, pack it into a proper metallic box and connect the ground of the circuit to the box to reduce noise effect.

12V Flyback Regulator Circuit

This is a design circuit for flyback regulator using LM2587. This is the figure of the circuit.


When the switch is on, current flows through the primary winding of the transformer, T1, storing energy in the magnetic field of the transformer. Note that the primary and secondary windings are out of phase, so no current flows through the secondary when current flows through the primary. When the switch turns off, the magnetic field collapses, reversing the voltage polarity of the primary and secondary windings. Now rectifier D1 is forward biased and current flows through it, releasing the energy stored in the transformer. This produces voltage at the output. [Circuit source: National Semiconductor Notes].

Dual Rail Power Supply Circuit

This is a conventional type of power supply. Here’s the schematic of this circuit.


The power is applied through the step-down transformer (230/12-0-12V/500mA). The DC proportional to the charging input voltage is obtained from bridge rectifier. Two electrical are there to bypass any spikes present. Bridge is capable of handling currents up to 1 Amp.

Regulated DC Power Supply Circuit

This is a design circuit for regulated DC power supply. In this circuit is using short circuit protection and with current limiter. This is the figure of the circuit.


This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added. The power transformer should be capable to deliver at least 25A at 17.5 to 20V. The lower the voltage, the lower power dissipation. The rectified current will be "ironed" by C1, whose capacity should not be less than 40.000uF, (a golden rule of around 2000uF/A), but we recommend 50.000uF. This capacity can be built up by several smaller capacitors in parallel. The D2, R3 and B-E connection of the Q4 will sense the Uds voltage of the FET1. When the voltage rises enough, the Q4 will shortcut the FET1 gate to mass, and cut the current flow through the FET 1 off.

Sound Operated Relay

This circuit is design for control the audio specially for control the light. This circuit is not a voice operated switch (VOX) because this circuit is too dumb to differentiate between musical sound or human voice. This is rather a sound activated than voice activated. This is the figure of the circuit.


One interesting application is to control your disco lighting automatically by the musical sound from high power amplifier, when the music signal is dominating the sound space. For condenser microphone, you have to connect R1 resistor as shown by the dashed line. Choose between 1k5 ad 22k to adjust the sensitivity, or use a 4k7 value if you don’t care with the sensitivity fine tuning. Make sure the electrolytic capacitor is rated for 16 volt or more. The potentiometer shown in the schematic diagram is used to adjust the gain of the pre-amplification. You can adjust this potentiometer to get a proper sound level where the relay would be activated.

Delayed Startup Circuit

This is a design circuit that is controlled by LM2575 for delaying startup for pin ON/OFF. This is the figure of the circuit.


With an input voltage of 20V and for the part values shown, the circuit provides approximately 10 ms of delay time before the circuit begins switching. Increasing the RC time constant can provide longer delay times. But excessively large RC time constants can cause problems with input voltages that are high in 60 Hz or 120 Hz ripple, by coupling the ripple into the ON /OFF pin.