Hi Kevin,

Check this site :

http://www.angelfire.com/electronic/hayles/charge1.html

He did something same.
I am designing a similar circuit and have not even
asked tehse questions myself so i am interested in
ideas of others / your results.

grtz

Simon

>Hi Everyone,
> I am attempting to build a smart battery charger for
> NiMH batteries (8-AA), with a F877. I am going to
> use PWM to control a LM317, and sample the voltage
> with the ADC to look for the delta V.
> I was planning on: (I got these from Panasonic)
> trickle charge .05C which would be 5% duty cycle
> Soft charge    .20C which would be 20% duty cycle
> fast charge    .75C which would be 75% duty cycle
> I have a couple questions:
> 1.) What frequency should the PWM be ?
> 2.) Anybody know a simple circuit to control the
> LM317 with the PWM PIC pin ?
> 3.) How often should I use the ADC to look for the
> delta V to turn off or switch to trickle charge ?
> Any help would be appreciated.
>
> Thanks,
>         Kevin
> PS. I am a programmer not an EE, if you couldn't
> tell from above :)
>


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