Circuit Diagram Used To Measure The Resistance Of An Ldr. Therefore no current will go from the collector to the emitter of the transistor. The circuit symbol which is used for the photoresistor or the light dependent resistor is a combination of the resistor animated to indicate that the photoresistor is light sensitive in nature.
Hook up the circuit shown in the above diagram using an arduino uno or adapt it to any dev board with an analog input. The relay on when ldr uncoverd and relay off when ldr covered. First here s a quick demonstration of how to use an ldr.
The ldr circuit diagram works like this.
Ldr is a photoresistor is a light controlled variable resistor. Can be used in thermostats or heat activated fire alarms. This makes the voltage at the base of the transistor too low to turn the transistor on. We all know that the resistance of an ldr varies according to the light falling on it.
