Hands Free Faucets-The Solenoid Valve
The two technologies that, when combined, form a solenoid valve:
- 1. Electromagnetism (solenoid)
- 2. Fluid dynamics (diaphragm valve, or known as poppet valve).
A) Solenoids are electrical components that transform electrical energy into mechanical energy "motion". When energized a solenoid creates a magnetic field which exerts a linear force on an object called plunge or actuator. That's why solenoids are called "linear motors". Automatic faucets powered by batteries employ a type of solenoid called "magnet latching or bi-stable solenoid". These solenoids operate at low voltage, usually 6 volt DC, with some solenoids operating at 9 volt DC. The reason these solenoids are called "magnet latching" is that as the solenoid is initially energized to start the water flow, the plunger is driven into the range of a permanent magnet which in turn holds the plunger in the "open" position. This initial energizing of the solenoid is called "pulsing or inrushing" and takes place within a fraction of a second. In order to return the plunger into its original "closed" position the solenoid is once again "pulsed" but this time by reversing polarity (remember, we're working with DC voltage here). The reason behind this complex operation: Conserving battery power.
Faucets powered by AC transformers utilize standard, none latching solenoids. This type of solenoid requires constant energy to hold plunger in place, and when de-energized, the plunger naturally returns to its normal "closed" position with the help of a biasing spring.
In addition to Voltage specification, solenoids have Mill Watt specification. This last specification is especially important when dealing with battery powered automatic faucets since solenoids, by far, are the largest consumer of battery power in an automatic faucets. Mill Watt specification gives us a glance at solenoid's efficiency and the amount of current it needs to do its job. It's a sort of "miles per gallon" measurement, the more miles per gallon, given a specific size gas tank, the less gas stops we have to make on our journey. The same holds true in an automatic faucet, the more efficient the solenoid the less often we have to replace the batteries.