Obs. This project after be published in a Brazilian Magazine was included in my book CMOS Projects and Experiments (Newnes 1999)

Note that the SCR is a half-wave device, so the incandescent lamp glows with half of its normal brightness.

Power comes from the ac power line, and sensitivity is adjusted by R1. The sensor is an LDR that should be placed as far as possible from the controlled lamp to avoid feedback. The LDR should receive only ambient or natural light.

Any small transformer rated from 100 to 500 mA can be used in this project. An LED to indicate power on is optional.

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

 

Figure 1 – Schematics for the device
Figure 1 – Schematics for the device

 

A 200 peak inverse voltage (PIV) SCR is used in this circuit. This SCR must be mounted on a heatsink. Take care with the high voltage lines, using appropriate wires and avoiding any contact with external parts of the device

 

IC1 - 4093 CMOS integrated circuit

SCR - TIC106, MCR106, or 0106 (200 PIV) silicon controlled rectifier

D1, D2 -1N4002 or equivalent silicon rectifiers

LDR - CdS photocell, Radio Shack 276-1657

S1 - SPST toggle or slide switch

F1 - 5 A fuse and holder

T1 - 6.3 V, 300 mA, CT transformer

L1 - 5 to 200 W, 117 V incandescent lamp

R1 - 1,000,000 ohm - potentiometer

R2 - 10,000 ohm, 1/4 W, 5% resistor

R3 - 4,700 ohm, 1/4 W, 5% resistor

R4 - 1,000 ohm, 1/4 W, 5% resistor

C1 - 1,000 µF, 25 WVDC electrolytic capacitor

C2 - 0.1 µF ceramic or metal film capacitor

 

Datasheets


N° of component