09/08/2025
Had a question from one of our customers today regarding the standard machines and switching the to the newer 200A solenoids from the standard 125A we were offering the past as they're shaped differently. Here's my response:
Considering you're just using a standard motor, the connections and concepts of the solenoid are super simple. The solenoid is just a big switch or relay. You connect a low current circuit to activate a high current circuit. Inside the solenoid is a plunger that when depressed, connects the high current circuit which is exposed on the solenoid by the two really big terminals at the end of the solenoid. That plunger is activated by a magnetic coil inside the solenoid and exposed by the two small terminals on the solenoid.
So basically, there are two circuits:
High current: positive from battery -> solenoid big terminal 1, solenoid big terminal 2-> motor terminal, motor body -> ground/negative battery terminal.
Low current: positive from battery -> switch white/ribbed wire, switch black/smooth wire -> solenoid small terminal 1, solenoid small terminal 2 -> ground.
So when you click the switch, you're completing the low current circuit with the control terminals of the solenoid so that the magnetic coil in the solenoid energizes, the plunger fires and that completes the high current circuit on the large terminals. You can strip out the voltmeter and fan circuits for testing. It also doesn't matter which side of the terminals is +/-. I usually mount the solenoid upside down to protect the terminals and shorten the lead between the solenoid and the motor. Where the positive comes in from the battery to the large terminal on the solenoid, you'll want to use that for the positive on the switch, voltmeter and the fan; it will be a busy little terminal. Once you get the concept, debugging machines becomes a little easier and you can swap in any 12VDC solenoid in an emergency, but keep in mind the continuous/intermittent duty ratings of whatever you use as when a solenoid tends to fail, they usually weld the contacts and the machine will not cut off and the lower the rating, the sooner those will fail. You can flip off the safety switch at the battery or tap the top of the solenoid with a hammer to break the weld and stop it. Usually before that happens, you'll notice a little sticking when you're lure operating and that's when you need to swap the solenoid out.