Supercapacitors

[Harry Bloomfield]

Clive Arthur explained :

No need for the meter to be connected all the time, just a few seconds to get a reading.

14:00 5.01v 14:20 4.83v

[Dave Plowman (News)]

Thought their main purpose was a very high maximum discharge current for their size?

[Clive Arthur]

There are essentially two types, some for effectively replacing small batteries for memory etc, and some for supplying and absorbing rapid short bursts of welly. The former tend to look like ordinary capacitors, the latter have much thicker tabs to take the current.

Cheers

[Harry Bloomfield]

Harry Bloomfield formulated on Monday :

19:55 4.45v

Its looking very promising.

[Swer]

That?s just one of their main purposes. The other obvious one is that they don?t have a limited life like a battery does.

[tabbypurr]

If your figures are correct it's simple to work out how long it'll keep it remembering for. Others have explained.

NT

[tabbypurr]

If that's from 5v, somewhere in the region of 80 minutes then

NT

[dennis]

Most of that drop will be from the few seconds the meter is connected unless its a very high input impedance. It won't be.

[Bob Eager]

My meter is > 10megohms, so it wouldn't discharge that much ...

[tabbypurr]

AFAIK all digital multimeters are high R_in.

[Harry Bloomfield]

[e-mail] formulated the question :

Yes, I am well aware of that - it was the self discharge I was stuck on, I had no figures and no experience of.

My tests suggest it will do the job more than adequately. The spec. of the IC says that when it fails to be maintained by its backup battery, it defaults to an entry code of 0 (a single press of the zero button). Simple plan is to disable zero button and not use a zero in the access code. I have other ways to get in, if the code lock fails.

[Bob Eager]

Which means "won't be" is nonsense.

[dennis]

50micro amps at 5v how many meg?

[Harry Bloomfield]

dennis@home pretended :

It is a 25 year old LCD digital meter on the 20v range, so what will that be - 1M Ohm?

28 hours later, it is showing 3.94v.

[Cursitor Doom]

It's okay, Dennis the Dunce doesn't have a clue what he's talking about.

[Terry Casey]

I recall an article in Elektor magazine a few years ago which usewd them in conjunction with a cycle dynamo lighting system so that when the dynamo voltage dropped, the supercap turned a pair of high efficiency LEDs until the bike moved again.

(Cycle dynamos were still very popular until only about 5 or 6 years ago on the continent - not surprising when you could buy them for as little as ?5.)

[dennis]

CD still doesn't understand anything I see.

But then he probably doesn't even know what a micro amp is.

[Tim Streater]

Now then children, play-time's over. You will now write out your times tables up to 12 x 12.

[Clive Arthur]

<snip>

Yes, a clever idea. A bridge rectifier made from LEDs was driven by the dynamo with another LED and supercap on the bridge output providing the backup.

Cheers

[Cursitor Doom]

Dennis the Dunce seems to believe everyone is still using the old moving- coil 20kohms/volt (at best) analogue meters (as he presumably still is.) All the same, it's nice to see someone who's so relaxed about their own ignorance they're not afraid to display it to the whole world.