I bought a Chinese 36V 5A (presumably switch-mode) power supply from Ebay. OK, it was cheap.....
And because it was cheap, I thought I ought to test it fairly well before connecting it to anything. But how to do this? I hadn't got anything suitable for testing which used 36V... So I connected a spare 2596 drop-down board to the supply, intending to drop the output to 12V and power a cooling fan. That had a useful voltage display on it, but, within a minute of connecting it, as I was adjusting the output voltage to 12V, the display dropped to 0V.
That was odd. Apparently 0V coming out of the PS, but the 2596 was still displaying with its LEDs, and presumably drawing power. So I took a cheap Chinese voltmeter (are you beginning to see a trend here?) and looked at the input. The voltmeter went haywire for a bit, then registered 0V, and I assumed that the PS had given up the ghost. But when I then tested the multimeter, that seemed to have failed as well. It registered no volts on a new battery. So I had blown up a voltmeter?
I connected the 2596 board back, and it seemed to work for a while, then drop to 0V. I thought that maybe the PS had failed in some way that produced an AC output, so I took it over to a scope and looked at the output. The scope showed a nice clean DC output. Of around 15V.
So I took another (working) cheap voltmeter, and checked the output. This produced a reliable reading. Of 52V. And it didn't blow up.
I am now confused. I suspect that the power supply is actually working properly, and that I am testing it incorrectly, but I can't think of what I can do to confirm or disprove this. I don't really want to connect it to my stepper motor circuit until I am reasonably sure that it is working. Has anyone got any idea what I can do to give it a decent test? Without blowing up too much test equipment?
Failing that, can anyone explain what's been happening?
And because it was cheap, I thought I ought to test it fairly well before connecting it to anything. But how to do this? I hadn't got anything suitable for testing which used 36V... So I connected a spare 2596 drop-down board to the supply, intending to drop the output to 12V and power a cooling fan. That had a useful voltage display on it, but, within a minute of connecting it, as I was adjusting the output voltage to 12V, the display dropped to 0V.
That was odd. Apparently 0V coming out of the PS, but the 2596 was still displaying with its LEDs, and presumably drawing power. So I took a cheap Chinese voltmeter (are you beginning to see a trend here?) and looked at the input. The voltmeter went haywire for a bit, then registered 0V, and I assumed that the PS had given up the ghost. But when I then tested the multimeter, that seemed to have failed as well. It registered no volts on a new battery. So I had blown up a voltmeter?
I connected the 2596 board back, and it seemed to work for a while, then drop to 0V. I thought that maybe the PS had failed in some way that produced an AC output, so I took it over to a scope and looked at the output. The scope showed a nice clean DC output. Of around 15V.
So I took another (working) cheap voltmeter, and checked the output. This produced a reliable reading. Of 52V. And it didn't blow up.
I am now confused. I suspect that the power supply is actually working properly, and that I am testing it incorrectly, but I can't think of what I can do to confirm or disprove this. I don't really want to connect it to my stepper motor circuit until I am reasonably sure that it is working. Has anyone got any idea what I can do to give it a decent test? Without blowing up too much test equipment?
Failing that, can anyone explain what's been happening?