Josh Koffman wrote:
> Alternatively I could use PWM and some sort of home built driver. The
> circuit here: http://www.solorb.com/elect/solarcirc/pwm1/ suggests the
> use of a FET. Having never controlled this large a DC load before, I
> have no idea if this is a good or bad idea. Any thoughts?
>   
Basically, where I'd start is to drive a fet with the PWM output from 
the PIC, and use that.  The schematic you reference above basically does 
the same thing but with an opamp instead of a PIC generating the PWM.

Depending on the exact FET you use, and frequency, etc....You may need a 
FET driver or similar circuit, if you can't find a fet which will switch 
the 11 or so amps fully on when driven directly from the PWM output of 
the PIC.   And 'driver' might be as simple as another transistor. 

-forrest


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