Re: Big capacitors

Roger Hamlett wrote:
"Nick" <me@xxxxxxxxxxx> wrote in message news:43e8ce89$0$64385$892e7fe2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I'm looking for a big electrolytic; at least 0.1F @ 16v.

Don't want to pay a fortune.

I'm in the UK.

Any ideas?

Nick
Depends 'massively', on what other features you want it to have..
You can get such a capacitance, in a very small space, by series connecting (with suitable resistors to ensure voltage balance), some of the 'memory backup' capacitors (supercapacitors). 3*5.5v 1F capacitors, will give you 0.33F. If you want something with better ESR etc., then the cost starts to rise.

Best Wishes

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.

So rather than spend £400 on a true UPS, I thought I'd try a big capacitor and a relay (to stop the capacitor shorting the supply) on the low voltage side of the wall wart.

Thanks again Roger.
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