At 02:45 PM 10/8/01 +1000, Jonathan Luthje wrote:
>G'day all,
>     I have a question relating to the 16F84A processor - basically all I'm
>doing is switching on and off a couple of relays via a 1.6mA base current to
>a pair of BF246 NPN transistors. There are 3 pins (RB0,1,2) set to output -
>the rest are set to input, some tied high, some tied low, all via 2k0
>resistors, all unused pins are tied together, set to input and tied to
>ground via a 2k0 resistor. I have regulated and filtered 6vdc supply rails
>powering the thing.
>
>The circuit and program were working beautifully up until the time where the
>circuit "browned out" and caused the PIC to get very hot (hot enough to put
>a blister on my thumb - ouch). I've since installed a reset-on-brownout
>circuit as given in the 16F84A datasheet. This is PIC #3 that this has
>happened to ... it's starting to get a little expensive! :)
>
>Is there some fundamental design flaw I'm making here?

One possibility: separate all the unused pins and turn them into
outputs.  I can imagine a situation where one port pin tries to go LO and
another tries to go HI.

Its a long shot but is easy to try.

dwayne



Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

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