Looking for BIG capacitors.

[phiscock-g851W1bGYuGnS0EtXVNi6w at public.gmane.org]

> Peter P. wrote:
>> and 3 AA NiCd (not NiMh) cells of the cheapest kind
> I thought NiMh replaced the very toxic NiCd cells.
> Can you even buy Ni-Cads these days?
>
Just to clarify, you can't just put a resistor in series with a voltage
source and 'trickle charge' one of these batteries, that will ruin it.
There are sophisticated IC's that manage the charging of these batteries.
Dunno about NiMH, but for Nicads, you need to charge at constant current
and then when the battery is fully charged drop the charging voltage and
carefully control the trickle current.

Look for 'Battery University' on the web for the gory details.

I'd support the suggestion of stealing the PC power. There are usually
spare connectors that could be used for this. The PC power supply could
easily supply the necessary power with no affect on the rest of the box.
The 4 pin connectors have +5V and +12V available at gazillions of amps. If
you do that, I'd recommend putting in a current limiting circuit of some
kind (fuse or electronic limit) so that a short circuit doesn't lead to
'flaming debris'.

Peter



-- 
Peter Hiscocks
Syscomp Electronic Design Limited, Toronto
http://www.syscompdesign.com
USB Oscilloscope and Waveform Generator
647-839-0325

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