Harold's suggestion is good, but it can be improved by using an
appropriate valued zener for the diode ... also gives overvoltage
protection.  It's saved my breadboard circuits from frying more
than once.
 - Nick -

Harold Hallikainen wrote:
>
>         How about a series PTC then a shunt diode.  The diode will conduct if
> the batteries are put in backwards, opening the PTC.
>
> Harold
>
> On Mon, 8 Nov 1999 05:26:07 -0800 mazzoni michele <mazzoni@TECHEMAIL.COM>
> writes:
> >Hello List,
> >
> >I have realized an alarm for my bycicle using a 12C508. It is powered
> >by two AA
> >size alkaline battery.
> >
> >I would like to know if there is a simple (and economic!!) solution
> >which
> >I can use to protect my circuit against polarity inversion during
> >battery change.
> >(I know it's a remote possibility, but it exists)
> >
> >I thought to use a serie diode, but the voltage drop bring the PIC
> >power voltage
> >near the power supply limit of the MCU.
> >
> >Thanks.
> >
> >
> >Best regards,
> >Michele
> >
> >_______________________________________________________
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