Author Options:

Any idea how I should go about switching ON/OFF 120VAC solenoid valve using Arduino? Answered

The solenoid's datasheet doesn't mention a required current, but it does specify it uses 16.1 Watts, so at 120V I'm assuming it's ~134mA. irs.gov

The only relays I can find for that voltage, have a minimum current rating of 1A. Would I have more luck using a MOSFET / NPN Transistor? Any advice would be helpful fedloan



22 days ago

I would not go with a mains powered relay.
5V relays that you can power with a tiny transistor directly from the Arduino do the same.
For a solenoid valve, if there is no 12 or at least 24V option available I would opt for a full isolation between electronics and relay.
One simple option is to use a optocoupler and from the output you can power a small relay that controls the mains power for the solenoid.
Another neat, although slighty more costly alternative is to use a SSR - Solid State Relay.
You only need the smallest type and they can be powered directly from the Arduino with 5V.
A SSR includes all the required isolation, is silent to operate and only switches when the mains voltage is at zero, so no transition spikes or similar from the solenoid valve.
If you after long term reliablility or expect really frequent switching then SSR is the way to go.


22 days ago

There are so called "relay boards" who already include everything to switch the relay. You just need to supply them with 5v (for example the power supply of your Arduino) and send a signal to them. This should do the job.