The fast switching action of the 4093 helps obtain a night switch circuit that does not become unstable when on the threshold of the triggering, causing oscillation in the lamp brightness.
A circuit for this purpose is shown in Figure 1.
This circuit is intended exclusively for the control of incandescent lamps up to 200 W and has its sensitivity set at P1.
For the assembly we suggest the printed circuit board shown in Figure 2.
The sensor is a common LDR that must be installed so as not to receive illumination from the lamp itself it controls. If this is not observed, we will have oscillations that destabilize the circuit.
The setting of the trigger point is made in P1 which can be either a potentiometer or a trimpot.
The transformer used is of the same type as we suggested in the previous circuit, the same as with the SCR. The SCR must be equipped with a heat radiator.
Also in this case, we have two sectors with low and high voltage feeds. Do not leave any part of these circuits exposed because they have points of connection with the power network, and can cause shocks by touching them.
The purpose of C2 is to provide the circuit with a certain inertia by preventing it from switching with flashes of light such as those occurring in an evening storm or shade if an object passes quickly in front of the sensor. The value of this component can be increased as required.
Material list
Semiconductors:
CI-1 - 4093 - CMOS integrated circuit
SCR - TIC106B or D - SCR according to the power grid
D1, D2 - 1N4002 - rectifier diodes
LED - common red LED (optional)
Resistors: (1/8 W, 5%)
R1 - 10 k ohm - brown, black, orange
R2 - 4.7 k ohm - yellow, violet, red
R3 - 1k ohm - brown, black, red
R5 - 1.2 k ohm - brown, red, red (optional)
P1 - 1 M ohm - trimpot or potentiometer
Capacitors:
C1 - 1000 uF x 16 V - electrolytic
C2 - 100 nF to 470 nF - polyester or ceramic
Miscellaneous:
T1 - Transformer with primary according to the local power grid and secondary of 7.5+ 7.5 V or 6 + 6 V and current between 50 and 300 mA.
X1 - 5 to 200 W - common incandescent lamp
S1 - Single switch
LDR - round common LDR of any size
F1 - 2 to 5 A - fuse
Printed circuit board, heat radiator for SCR, fuse holder, power cable, mounting box, lamp socket, wires, welding, etc.
