Photo Electric Strret Light

This is basically a Schmitt Trigger circuit which receives input from a photo cell and controls a relay that can be used to switch off and on a street lamp at dawn and dusk. I have built the circuit with a 120 ohm/12volt relay and monitored performance using a lamp dimmer, but did not connect the relay to an outside light

The photocell should be mounted above the light on top of a reflector and pointed upward at the sky so the lamp light does not strike the photo cell and switch off the lamp

The switching points are about 8 volts and 4 volts using the resistor values shown but could be brought closer together by using a lower value for the 7.5K resistor. 3.3K would move the levels to about 3.5 and 5.5 for a range of 2 volts instead of 4 so the relay turns on and off closer to the same ambient light level. The potentiometer would need to be readjusted so that the voltage is around 4.5 at the desired ambient condition.