The dispenser uses a sensor to measure the resistance of the sponge. If the sponge drys out too much the resistance goes up, microcontroller detects it and turns on the pump. I am using an arduino as the project is still in development. I'm planning to later replace it either with some microcontroller or simply an op amp. I am thinking about using a micro so there can be some error detecting mechanism programmed in. I don't want 3L of water to be emptied on the table if the sensor gets somehow disconnected.
Enjoy this project?