Photoelectric cells can be used as sensitive light sensors. However, the low voltage they generate when the light sources are weak requires a good amplification circuit. In the figure we show a circuit specially indicated for this purpose. The resistor R1, which can have values between 10 k ohms and 1 M ohms, will determine the amplification of the circuit in the desired application. A good practice may be to use a trimpot to achieve the desired sensitivity setting. The power supply must be symmetrical from 5 to 12 V and the sensor cell must provide a maximum voltage of 1.5 V.
