Dark-Activated Lamp Flasher (ART060)

The circuit works as follows. When light is striking sensor Q1, IC 1-a output is low, and the IC1-b oscillator is off. Thus, IC1-b is high, which results in a low IC1-c output and IC 1-d output. Transistor Q2 is cut, and the lamp is off.

When light drops off, IC1-a output goes high, and IC1-b oscillator turns on, driving the output transistor via IC1-c and IC1-d.

Transistor Q2 can drive lamps up to 500 mA and must be mounted on a heatsink. Sensitivity is adjusted by R1, and flash rate is adjusted by R2.

You can replace the potentiometer with a CdS photoresistor. In this case, also replace R1 with a 100 kg potentiometer.

A schematic diagram of the Dark-Activated Lamp Flasher is shown in Fig. 1.

Figure 1 – Schematic diagram of the Lamp Flasher

Transistor Q1 must be mounted on a heatsink. Observe proper positioning of polarized components such as transistors and the electrolytic capacitor.

Q1 is mounted inside a tube and, for a more directional performance, you can include a convergent lens in the front of the tube.

To operate the unit, adjust the sensitivity using R1 to the dark level required to trigger the circuit.