Dimmer / AC motor speed controller

If you want to control the light level of a room or if you want to control the speed of a drill or a fan (devices that use AC motors), this is the circuit you are looking for

Differential Temperature Controller.

This circuit measures the temperature difference between 2 sensors and activates a relay when they are different

Water Level Controller Circuit

This simple Water level controller circuit is useful to control the water level in a tank. It does this by turning On and Off a water pump depending on the status of the sensors.