Light-controlled switch circuit diagram of photoresistor (LDR)

As shown in the circuit in the figure, when there is incident light, the transistor connected to the photoresistor LDR in the circuit is turned on to high level or zero level. It is sufficient for the transistor amplification factor to be B>100, and the photoresistor resistance is between 100 and 100k ohms, corresponding to the conditions of light exposure and darkness respectively. If you want to control a larger power load, you should use a Darlington transistor . ck="window.open(this.src)" alt="Click to see larger image"/>