Fixed my high pitched fan (electrical) noise
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So I have a super annoying high pitch whine on a pair of Sunon 12v fans (MF25101V1) in a push/pull on a mosquito clone. While I'm replacing the hot-end heater I figure it should be an easy thing to either fix or identify why my fans have this high pitched induction coil whine that slowly claws at your soul. Might as well fix while things are torn down... and into the rabbit hole i dove. Threw my scope on it since I felt like it was some electrical noise was carrying through to the fan motors. Of course I did, I'm using switched mode supplies. Regular 12v rail had all kinds of electrical noise at 500Hz, 1kHz, and 100kHz.
Well, somethings causing it right? Let's start with filtering some culprits out. I try a capacitor to filter it... nothing. Ok well, a temporary voltage offset on the noise but the waveform didn't change at all? Fine...grab a toroid and do a simple choke...scream.. multiple LC filters ...and still no response...Am I a ghost now? WTF is this sorcery?!
So eventually I snip a fan out and blissful silent air flow... So it turns out that the issue was running two fans off the same cable right up to their own leads... Noise is gone soon as each fan gets it's own wires back to the terminal strip (they're wired always on).
I'm just happy the noise is gone and won't question why I've never had an issue wiring this way before. Still I thought I'd share in case someone has a whine / high pitched noise they can't get rid of, then here's one possibility.
TLDR; Parallel DC Fans sharing a power cable can cause high pitched feedback sometimes, intermittently, and in just the right way to test your sanity.
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@lord-binky said in Fixed my high pitched fan (electrical) noise:
turns out that the issue was running two fans off the same cable right up to their own leads.
Thank you for sharing your experience, this was an interesting report!
