Faucets. Toilets. They both use proximity sensors to determine when a user is present and then turn the water on when the user is away or present. This is that type of circuit but with a relay that can handle a relatively high current load of 10 amps. An adjustable on time from 0-30s. Building the circuit helps get a sense for how it works. The potential applications are limitless.
In this circuit the relay is triggered on when an object is within range of the proximity sensor.
This product comes unassembled and requires soldering.
2 Sets x Infrared Proximity Sensing Relay Module