Re: [avr-chat] Running AVR off a supercapacitor & USB?

[Graham Davies]

Pertti Kellomäki wrote:

> Would it be possible (and practical) to run
> a small AVR board off a supercapacitor, which
> would every now and then be topped by plugging the
> board into a USB cable?

What kind of AVR board?  Doing what?  What kind of supercapacitor?  The kind
put in electric vehicles or the kind used instead of batteries in electronic
equipment?  What do you mean by "every now and then"?

> I have no idea of prices and availability of
> supercapacitors, so this might be completely
> impractical, but the idea is rather tempting.

Well, why not find out?  For example, Digi-Key have a Panasonic high-value
capacitor of 1 farad, 5.5V in stock at $5.41 for one piece.  One farad will
give you one coulomb of charge per volt.  So, if you charge to 5 volts and
your AVR will keep going down to 3 volts you have two coulombs.  That's an
amp for two seconds or, more usefully, a milliamp for two thousand seconds
which is about half an hour.  Now we're stuck because you didn't provide any
information in your question for us to figure out what your power draw is or
how long you want to stay up before recharging.

Graham.