From: Winfield Hill
Subject: Re: Help - Power mosfets - difficult load
Date: 27 Oct 2002 03:17:22 -0800
Organization: Rowland Institute
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> Just in case you didn't already realise...
>>> 1) Considering fet temperature rise, I have in my favour the
>>> fact that the motor will be powered up for around 10 seconds
>>> at most, every 5 minutes or so at worst.
>> 10 seconds is in your favor, but thermally 5 minutes is forever.
> I was unclear here. I meant that worst case overall duty cycle
> would be 10 secs on, 5 mins off.
Oh, that's another matter entirely. You can guareentee ten
seconds max, even if by assertion of careful manual operation?
If so you can rely on the thermal mass of certain components,
for example, using only a small heat sink, or more accurately
a small aluminum or copper heat block. Cooling fins would not
be needed, given a 5-minute off time, although you'd also have
to stick to short test bursts during the debugging phase.