This is a home, store or garden utility project. With it, we have the automatic ignition of an incandescent lamp (do not use another type) at dusk and shutdown at dawn.
Incandescent lamps up to 100 W can be controlled and at the standby condition, i.e., during the day, the energy consumption is practically nil.
The circuit uses as a sensor an LDR which, when darkened, triggers the SCR and with that we have the lamp on. In fact, the SCR used admits larger bulbs, but operating with a certain break it does not need a large heat radiator.
The LDR must be installed so that the light from the lamp which it controls can not be noticed, because if this occurs, the circuit will oscillate with the lamp blinking.
The sensitivity of the trigger is set by means of a potentiometer.
In Figure 1, we have the complete circuit of the device which can operate in both 110 V and 220 V power grid.
The arrangement of the components on a terminal bridge is shown in Figure 2.
The SCR must have the suffix B if the network is 110 V and suffix D if the network is 220 V. The capacitor C1 must have a working voltage of 250 V or more and the LDR can be of any type or size.
This LDR must be installed in an opaque tube and pointed at the sky to detect blackness and when it is brighten. To test, just plug in the device, plug in and uncover the LDR while adjusting the sensitivity.
We note that the brightness of the lamp will not be maximum when lit, because SCR control is half wave.
Material list
SCR - TIC106B or D - Silicon controlled diode (see text)
D1, D2 - 1N4004 for the network of 110 V or 1N4007 for the network of 220 V - silicon diodes
R1 - 47k ohm x 1/8 W- resistor - yellow, violet, red
P1 - 1 M ohm- trimpot or potentiometer
C1-470 nF-polyester capacitor
X1- incandescent lamp from 5 to 100 W
Miscellaneous:
Terminal bridge, power cable, SCR radiator, assembly box, wires, welding, etc.
