Light Sequencer Circuit

Posted on Oct 18, 2012

The light sequencer uses two ICs and 10 SCRs to ac sequencer. The first 10, a 555 timer, is used to provide clock pulses for 102. The 10 is configured as an astable multivibrator, and its output is on pin 3. Capacitors CI and 04, along with resistor R2 and potentiometer PI, control the frequency of the pulses. IC2 is a 4017 Johnson counter, which shifts a high-signal level to each one of its 10 output pins in sequence. Each output pin is resistively coupled to the gate lead an an SCR. When the respective output pin on the 4017 is high and the positive half of the ac cycle is on the anode lead of the SCR, it turns on.

Light Sequencer Circuit
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The lamp that is connected to its anode lights. Power is brought into the PC board by the line cord, then the circuit is fuse-protected. Diode LD1 changes the ac to pulsating, which is smoothed by C2 and C3. R23 limits the current, and zener diode D2 limits the dc voltage to 6 Vdc.

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