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DC motor soft start

I found this neat soft-start circuit on the eevblog forum. Its neatness is that the gate threshold voltage occurs immediately and then the RC softness kicks in.

V+ ________________________ V+ | | 1M ___________ V- |___1u___| | | | |-- |------| |-- | V- ____________|

As neat as that is, I have a situation where the motor may be run in either direction (either polarity on the input) and the soft start circuit won't handle that. To use it with either polarity, I plan to use 2 of them & isolate with diodes:

_______ V+/- -x-----D>--| |---------x-----V+/- | | | | | | |-----x---------V-/+ V-/+ -----x-__| |_____| | | | | | |_____

Reply to
Bob Engelhardt
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could do this perhaps?

__________ V +/- .--SS--'

maybe add a diode parallel with the 1Ms to make faster resets.

None that's worth bothering with.

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  Jasen.
Reply to
Jasen Betts

That would work ... clever, too. Thanks.

I'm guessing that the "S

Reply to
Bob Engelhardt

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Reply to
Jasen Betts

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OK ... I built this and tried it out. Didn't work as expected & when I put my scope (Tek 465) on it, I couldn't see the trace. It's a 1-shot sort of event & the scope doesn't have the persistence (let alone storage) to see it. Any good tricks for seeing non-repetitive events?

Thanks, Bob

Reply to
Bob Engelhardt

long exposure photography on your scope screen. take a video recording of the scope get a storage oscilloscope. use a sound-card and software PC oscilloscope

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  Jasen.
Reply to
Jasen Betts

I have an iPhone camera - no shutter control. But I just found a feature that does a virtual long exposure (Live photos & Effects). I'm gonna' try it.

Reply to
Bob Engelhardt

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