Vehicle Interior Lighting With Switch-Off Delay

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

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

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

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

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]