With the configuration shown in the figure, a common 12 V lamp lights up when light no longer strikes the sensor. An interesting possibility is to use for B1 a rechargeable battery (Nicad) coupled to a simple charger circuit, as shown in the same figure. In this way, when there is power failure and no light is on the sensor, the emergency light will come on. The sensitivity to triggering is set to P1. If there is a tendency for tripping with the passage of shadows rapidly in front of the sensor, a capacitor of 1 to 10 uF can be connected in parallel with the sensor. This component will also prevent the lamp from turning off with flashes of light, for example a lightning strike.
