[sdiy] Supercaps!

[Bert Schiettecatte]

Sure, but can't you circumvent that by using some circuit to boost the
voltage and keep it regulated until the cap has discharged almost
completely?

-----Original Message-----
From: Roy J. Tellason [mailto:rtellason at blazenet.net] 
Sent: maandag 9 augustus 2004 0:58
To: Bert Schiettecatte
Subject: Re: [sdiy] Supercaps!


On Sunday 08 August 2004 06:32 pm, Bert Schiettecatte wrote:
> Hi All,
>
> I came across super capacitors while browsing some catalogues, and I 
> am interested in trying to power an Atmel ATTiny26 from a supercap for

> one hour or so. While googling for supercapacitors and 
> microcontrollers I found this information:
>
> http://ww1.microchip.com/downloads/en/DeviceDoc/51337a.pdf
>
> It says on page 21 of this document: DO NOT use this circuit as a 
> general design practice. I am a bit puzzled now. Some other 
> electronics guru today told me he would never use a supercap for 
> powering a device except a PIC in sleep mode (what this app note is 
> all about). What is wrong with powering something with a super 
> capacitor? It seemed like a very cool idea instead of going through 
> all the hassle of builing a lithium-polymer battery circuit to power 
> my microcontroller...
>
> Any comments? Suggestions? Super cap hate mail?

It would seem to me that the discharge curve with any nontrivial current
draw 
would be what would make such a use a not real terrific idea... 

That curve starts out darn near vertical.