Review on ⚡ Ultimate Electric Solenoid: The Unbeatable Normally Closed Solution from U S by Doug Virden

I use it as an on/off valve on a sprayer and it works well so far, the construction feels really solid. Coming from the industrial automation world the price is amazing, probably 10% of what I would expect for a similar device from my usual industrial sources. A word of caution for those unfamiliar with electronic circuits. The DC resistance of the solenoid is 7.35 ohms and therefore draws about 1.74 amps. When you turn off the solenoid, the magnetic field collapses, creating the reverse polarity voltage needed to instantly maintain 1.74 amps. Without an alternative path, the field collapse creates enough voltage to arc across the switch and relay contacts, quickly deactivating/destroying them. Do yourself a favor and connect a 1N5404 diode or similar in parallel with the magnet, the cathode to the + terminal and the anode to the - terminal. In this way, when the field disappears, a current pulse flows through the diode and protects your switching devices.