The design presented here consists of a simple light relay that triggers a relay when light strikes an LDR.
In figure 1 we have the circuit that uses as a sensor a common LDR and whose sensitivity is set at P1.
The assembly may be made in a contact array or a terminal strip with the array of components shown in Figure 2.
The resistor is 1/8 W with any tolerance and the LDR is of the ordinary round type.
The relay can be either 6 or 12 V depending on the voltage used in the power supply and if the mounting is in matrix, type with DIL base must be used.
Material list
Q1 - BC548 - NPN general purpose transistor
D1 - 1N4148 - general purpose diode
LDR - round common LDR
P1 - 100 k ohms - potentiometer
K1 - 6 or 12 V sensitive relay
B1 - 4 batteries or source - 6 or 12 V
S1 – On-Off switch
R1 - 1 k ohms - resistor - brown, black, red
C1 - 100 uF x 16 V - electrolytic capacitor
Several:
Terminal strip or protboard, battery or source holder, wires, solder, etc.
