I bought a 2nd-hand 12v 2A power supply without branding. I intend to use it on a DVD player. Coming from the street market makes it dicey because anything in that market could be from someone’s dumpster dive. To ensure it’s useable I used a DMM to measure the volts. It started at 18v but continued to gradually climb. When it passed the 20v scale on the DMM, it quit reading. So it would probably go even higher in the next scale.
I expect the voltage to be higher than rated because the 12v rating is expected to be a measurement under load. But my whole point is to check whether it is safe /before/ driving the appliance. Seems strange how the volt reading kept increasing. Is that expected? Is there another test I should do?
I have an Arduino kit with a variety of resistors. Would I just take any resistor to use as a dummy load, or does it matter which resistor I use?
The PSU is rated at 2A 12v, so would I take 2A÷12²v? Should I look for a resistor that’s 0.0139ꭥ? My EE class was decades ago, mostly forgotten.
I also have a 12v LED lamp that I pulled from a dumped refrigerator which I could sacrifice.
I’m often in a situation of needed to repurpose dodgy PSUs with dodgy appliances, so I’d like to generally know how to do this.
You would want big thermal resisters, or something that doesn’t care about the correct voltage like a big beefy motor
In that case, it sounds like I should try using the PSU to hotwire the universal motor in my washing machine.