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Nick Alexeev
Nick Alexeev
4:56 AM
@Lundin What's the frequency of the solenoid signal (drive) ? How much current?
What you're trying to achieve isn't out of the question. I've seen sine wave stepper motor drivers. They were linear (not PWM) because they had to work with sensitive electrophysiology equipment. The followed the DAC + opamp+ power BJT pattern.
 
1 hour later…
Lundin
Lundin
6:13 AM
@NickAlexeev There's 2 frequencies: the regulation PWM which is avoided with a DAC. And another low frequency of the output, typically need 80Hz or so. It's hydraulic valves/motors and you just need apply a bit of stirring to prevent them from getting mechanically stuck before moving. The 80Hz I don't see as an EMC problem. Currents are up to 1A per output.
I've designed lots of systems for valve current control but never with extreme EMC requirements (MIL-STD-461 and then some).
My colleague who designed the DAC + opamp + BJT is an EE veteran and we've both worked a lot with military EMC but now we are stuck. I suppose fiddling around with the BJT and getting something more similar to a sine wave than a sawtooth could work EMC wise.
 
8 hours later…
User1974
User1974
2:18 PM
As a non-electrician person, it surprised me how hot corded chargers like this get if covered by something: https://i.sstatic.net/H3QRddzO.png
My coat fell off of its hook and partially covered this charger. It was too hot to touch and seemed like a fire hazard.

I figure the smaller chargers that live right in the socket are likely safer. Less likely for something to cover/insulate it. https://i.sstatic.net/lygNJY9F.png

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