Re: Big capacitors

Nick wrote:
Thanks for the magic words 'memory backup'; I see even Maplin sell them.

I need them to keep an ADSL modem alive during mains brownout
conditions. Tried a cheap UPS but it didn't stop the brownouts reaching
the modem and latching the firmware/hardware.

Hmm, typically these will draw several hundred mA. A 0.1F capacitor
will keep the supply up for a few seconds, which may be enough or may
not.

It seems rather more straightforward to get some batteries
always-being-trickle-charged instead.

And you might want to stay away from the "memory backup caps" (which
are optimized for a discharge current way below a mA) and stick with a
conventional electrolytic. 100000uF at 16V is like $10 here in the US.

Tim.

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