Hi folks,
OK, this will be some kind of off-topic, but it is of course related to
electronics.
My sister's birthday is coming up, and I decided to build her a binary
clock ;-) See the schematic here:
http://www.jb-electronics.de/tmp/clock_schematic.png
See the PCB and the housing here:
http://www.jb-electronics.de/tmp/clock_pcb_1.jpg
http://www.jb-electronics.de/tmp/clock_pcb_2.jpg
http://www.jb-electronics.de/tmp/clock_housing.jpg
The idea was to have it battery-buffered, so that she could simply
unplug the wall wart power supply and the clock would keep running with
the LEDs shut off. To do so, the PIC checks if main power is turned on
or turned off with software (over RA2). If it is turned off, the PIC
goes to sleep(); and an interrupt increments the time every 2 seconds
using the clock crystal on RB6, RB7.
Anyway, this worked just fine, or so I thought.
In a little test run, the clock was connected to the main power supply
(wall wart) and worked fine. I let it run for about 1 hour. Then I
removed the wall wart, and it switched to battery. But now get this: The
PIC suddenly got really warm, and when I re-activated wall wart power,
nothing happened. The PIC cooled down, though, but the software hung. So
I removed the PIC, removed the batteries, reinstalled everything, and
the problem has not occured since.
I have had the clock running for another hour now, removed the wall
wart, plugged it in again, and so on, but the PIc keeps cold like ice
and works wonderfully fine as expected.
But I am quite confused. Why did something happen in the first place?
Thanks for your time, I hope you can help me.
Best whishes,
Jens
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