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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Help - Power mosfets - difficult load
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Date: Thu, 24 Oct 2002 01:55:13 GMT
NNTP-Posting-Date: Wed, 23 Oct 2002 21:55:13 EDT
Bill Allison wrote:
> Hi John
> Have to say thanks for the effort you're putting into this! I'm amazed
> at the amount of interest shown by all. Yes - I had planned to use a
> 4.8v nicad trickle charged via hi value resistor from the 12v to
> supply the RC receiver and control system. And a 9.6v nicad
> (10.something fully charged on load) for the gate drive IC so that
> stiff drive is guaranteed and the 12v rail is powering only the motor
> / fet / diode circuit.
Don't be surprised if you find that the big battery bounces 5 or 6
volts during the pulse cycle. I suggest you run the gate driver off a
second source, so that you don't risk having the fets go linear on you
as the motor battery sags.
> I do have a 2 channel scope and sure, I can find a way of measuring V
> and I in the fet. Easy with initial tests 'cos of course I'll put some
> low value resistance (low inductance I hear you scream...) in series
> with the motor.
No screaming, here. :-)
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