The Self Closing Basin Taps typically controls a solenoid-activated diaphragm VALVE. The solenoid is an electromagnet that can push or pull, depending on electric polarity. Diaphragm valves use a rubber-like disc to control water flow. The valve is normally held closed, but in response to a sensor signal that hands are present, the solenoid pulls the valve open so water can flow out the spout, then pushes the valve closed again when the sensor says the hands are gone. Most touchless faucets dispense only warm water, but some models can provide hot or cold water.
Power Source
All touchless faucets require a power source. Some models draw power from dry-cell batteries, while others use a low-voltage current from an AC transformer. Electricity powers the sensor, control electronics and water valve. Battery-powered faucets use latching solenoid valves that stay in the open position without further electric current until a spurt of power pushes them back to the closed position. Transformer-powered faucets use continuous electric current to hold the solenoid valve open.
Spouts
Touchless faucet spouts, which hold all the working parts, are made of zinc in cheaper models, while the high-end models are made of brass. They may be plated with nickel or chrome for durability and appearance. The spouts may be machined, die cast or sand cast. There are different styles of spouts for standard bathroom or kitchen use, lab sinks, bar sinks and food service sinks. The spout also is where aesthetics come into play. The shape and finish of the faucets