The basic idea of the circuit shown in the figure is to increase the brightness of an ordinary incandescent lamp when the amount of ambient light that strikes the sensor decreases. Placed in a room, it will cause the lights to increase in brightness as it gets dark, this being the case with the opposite effect at dawn. Of course, the same configuration can be modified to operate with other types of sensors. Thus, if instead of the LDR we use an NTC, and as a heater load, the circuit will heat an environment when its temperature decreases, functioning as well as a thermostat. Of course, depending on the desired control range and the sensor's own characteristics, changes in component values may be necessary. The TRIAC used with suffix B operates on the 110 V network and with suffix D on the 220 V network allowing control of load currents up to 8 amps.
