PIC power backup with "super capacitor"

[Luciano]

Hi,

See this link:
http://www.qsl.net/zl1bpu/MICRO/CLOCK/index.htm

From the above link:
When the AC supply fails, D3 conducts, D4 is reverse biassed, and the
clock continues to operate from the battery with no loss of time.
However, since R2 is no longer able to keep micro input PD2 (pin 6) high,
the micro detects power failure and displays a "BATT" message. The battery
can be a small alkaline 9V type if power failures are rare, and will last
normal shelf life. If power failures are frequent or the clock is used as a
portable time source, a 6-cell 500mAH or better NiCd or NiMH battery pack is
recommended. R1 can be added to slowly charge the battery from the AC supply.

Schematic:
http://www.qsl.net/zl1bpu/MICRO/CLOCK/CLOCK2.GIF

* * * *

Best regards,

Luciano

[sayzer]

...

Schematic:
http://www.qsl.net/zl1bpu/MICRO/CLOCK/CLOCK2.GIF
...

Luciano,

9V battery in that schematic is indeed a good idea.

Thanks.

[flotulopex]

Well,

So many ideas..... :-)

I think, I'm going to make it the simple way first.

I found a super cap on an old PC motherboard so give me a few hours and I'll come back with some news.

Thanks to everybody for all your information. Really Great ;-)

[skimask]

Well,

So many ideas..... :-)

I think, I'm going to make it the simple way first.

I found a super cap on an old PC motherboard so give me a few hours and I'll come back with some news.

Thanks to everybody for all your information. Really Great ;-)

By the time you get done messing with a super-cap, you might find (as I did) that a diode-protected lithium coin cell might do exactly what you wanted the super-cap to do, easier and possibly cheaper (with an occassional replacement). I just wish I could find NiMH coin cells in similar size to the lithium coin cells...for cheap anyways...