I've had similar problems with all of my pic projects, the hardware solution
is a Motorola part MC33064 reset chip, three leads in a transistor package.
This is fairly reliable, 98% of the time. Using the watchdog timer seems to be
the software solution and is reliable. The power supply is not the issue, I
use $200
Hammond power supplies and the problem still occurs. If the POR fails then the
watchdog will bring it up after the timeout.

At 18:57 10/30/96 +0500, you wrote:
>I have a prototype circuit that, about 75% of the time, does not do a
>proper power-on reset.  The power supply is a wall-wart transformer with a
>10uF cap across the leads ffeding a 7805 regulator with a 100uF cap across
>+5V and gnd. (The capacitor values were chosen by the scientific method of
>looking into the junkbox and picking out what was in there)
>
>Is there a small, cheap external circuit I can build to guarantee a
>power-on reset?
>
>Thanks,
>        -Matt
>
>
>  "DOS Computers manufactured by companies such as IBM, Compaq, Tandy, and
>millions of others are by far the most popular, with about 70 million
>machines in use wordwide. Macintosh fans, on the other hand, may note that
>cockroaches are far more numerous than humans, and that numbers alone do
>not denote a higher life form."
>
>
 Thanks.
     __           Micheal Yano
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