Peter Cousens wrote:

> Tjaart van der Walt wrote:
> snip
> >
> > Ha! you saw the pitfall! Because I am just comparing the average drop, Ican check for overcurrent
> > (or undercurrent) anywhere in the loop. I had to
> > average the drop with a resistor and cap because I switch the MOSFET
> > hard on.
>
> I can't see how this is going to work ?
> Your I/voltage drop will be swamped buy the pwm off voltage and will
> be 99% dependant on your pwm mark/space
> ie: when the fet is off it looks like your drawing lots of amps
>
> I know you don't want additional heat but a resistor will probably be
> the
> best (with the opamp you only need very low Ohms)

The LM324 works down to 0V. I need the divider to bring the
voltages within the input range of the opamp. When the MOSFET
is on, the output of the opamp goes high. This difference is averaged
over the complete cycle.

--
Friendly Regards

Tjaart van der Walt
mailto:tjaart@wasp.co.za

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