Terry Pinnell said:
See the section of a fairly long thread, starting here, where I had a
lot of expert advice form Tony Williams:
Newsgroups: sci.electronics.design
Subject: Re: Simple 555 PWM - disappointing performance
Date: Thu, 26 May 2005 09:43:18 +0100
Thanks. I snagged the model, but only had time to browse the subsequent
discussion a bit; will read it more carefully later. I also didn't read the
fine print when I dl'ed LTSpice. Is it a demo with limitations? or is it the
real deal?
Anyway, it's a stepper, with much simpler physics than a PMDC. I'm more
interested in what's happening on the gate side of the MOSFET. Wondering if
I can't make it work with an opamp comparator for current sense/limiting
instead of the more traditional PWM chopping. Quad opamps are pennies these
days. I think I can squeeze a whole second motor onto the PIC if it can
off-load the current limiting part. (More for futzing around's sake than any
real economy. How many controllers would I need to make to recoup the $1.50
I save on the second PIC? What an upside down world. The protection diodes
alone cost more than the power MOSFETS.)