James,

What sort of reset circuit do you have on the PIC's /MCLR pin?  It sounds
possible that your circuits do not get a reliable startup reset.

One other possibility is that the current surge into the led circuits could
be causing the pic to operate strangely.  If the caps are discharged, you
will have 20mA of initial charge current.  If several of the leds are
commanded to be on at once, this could disrupt the pic.

This doesn't explain why your circuits always work the first time but not
subsequent times.  Are you 100% certain of this?  As far as stored charge
goes, the diode in series with the pic pin should avert problems there.

One other thought - if your batteries get low, their internal resistance
will rise and the startup surge could make the pic start up at voltage
levels too low for correct operation.

HTH,
Tom


At 11:46 AM 10/11/2003 -0700, you wrote:
>I have a simple circuit using a a 16F84A running with a 4Mhz crystal.
>
>I have 12 LED's that I want to randomly turn on and then fade out.
>Instead of using the chip to fade it out, I have a simple RC circuit for
>each LED.

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