AVR-Chat

OOPS!  Thanks for the catch.  I accidentally put in a P-channel fet.  

Anyways, the driver circuit is a small part of a larger circuit.  The
whole thing is reverse polarity protected by one diode on the +12V
line (which gets distributed to the rest of the parts... like this). 
If I tied the +12V line shown in this schematic, to the other end of
that diode, it won't conduct.  Therefore, any spikes above 12V won't
get shorted out.  Let me know if that makes sense, I can draw up a
quickie schematic addendum.

Ryan

--- In AVR-Chat@yahoogroups.com, Robert Adsett <subscriptions@...> wrote:
>
> At 12:28 AM 7/20/2006 +0000, Ryan wrote:
> >Alright, ideally, I could place a diode across the flyback source
> >(solenoid)... but in this case I can't.  (The solenoid is connected
> >remotely)  I can't figure out how to do this and provide reverse
> >polarity protection.  If I place a polarity protection diode on the
> >+12 input to the driver circuit, it will block any positive voltages
> >I'm trying to "short" to +12.
> >
> >Does that make sense?  I'm still a little confused myself.  See
> >circuit diagram here:
> >
> >http://i5.tinypic.com/20hjytt.jpg
> 
> 
> D2 is your flyback/freewheeling diode.
> 
> Add a diode between Aout and your diode pair if you want some polarity 
> protection on the load.
> 
> BTW Q2 is reversed, it will always conduct.
> 
> Robert
> 
> 
> http://www.aeolusdevelopment.com/
> 
>  From the Divided by a Common Language File (Edited to protect the
guilty)
> ME - "I'd like to get Price and delivery for connector Part # XXXXX"
> Dist./Rep - "$X.XX Lead time 37 days"
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> Dist./Rep - "that is the lead time given because our stock is
live.... we 
> currently have stock."
>