Re: Prob. a very basic Q re: capacitors

Kris Krieger wrote:
Joerg <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote in
news:MsHjk.15101$cW3.10285@xxxxxxxxxxxxxxxxxxxx:

Rich Grise wrote:
On Mon, 28 Jul 2008 12:09:13 -0500, Kris Krieger wrote:

How is the flow of power out of a charged capacitor be controlled? I've been loking at whatever circuit diagrams I can fond that use
supercapacitors as an energy source, and I'm not clear on whether
control is via the resistors, or transistors.
Supercaps are NOT an energy "source" - they'd be a storage medium, at
best, and they even suck at that.

A battery can store millions of times as much energy as a cap.

But it'll die of exhaustion pretty soon. a lot of stuff gets thrown in
the trash because the rechargeables are nearly dead and too expensive
to replace. Adding Cadmium and other goodies to the landfills.


Yup, that aspect of them really bothers me. Plus, I personally have a probably-irrational level of sheer annpoyance at ahving to replace things all the time - light bulbs, batteries, and other stuff as well ;) I have this admittedly-bizarre notion that everything should last for at least ten years <L!> Yeah, I know it's goofy, but there it is ;)


Same here. And the stuff I design usually _does_ last much longer than 10 years. Heck, the very first ultrasound machine I helped design over 20 years ago is still used and often traded:
http://www.steineredv.de/med/51/435/

Another where I designed parts of in the early 90's is the same. Talked to the CEO recently and he said that they still service a lot of them. The only things that "break" is a worn out monitor and the occasional power supply damage after lightning struck or something. Kind of makes me glad.

I am still using some tools in the lab that I built as a kid over 30 years ago, such as these:
http://www.analogconsultants.com/ng/images/oak2.jpg
For some reason none of this ever needed fixing.


At any rate, I'll design e bodies of my stained-glass tunits so that the Solar "stuff" (it'll all be in/attached to the top/"lid") can be removed, so that, if/when it dies, the main body of the stained-glass piece can still be used as a candleholder or some other form of decor. But I like the idea of a long-lived power source, so teh capacitor-as-"battery" idea also appeals to me aesthetically in a weird sort of wayI don't know how to explain.

But that's why I was wondering about "flow control". I still have waaaay more knowledge-*gaps*, than knowledge, so I'm probably thinking of this totally wrong, but if electricity is analagous to waterh, with Volts as "water pressure" and current as "flow rate (amount of water that goes through over a given period of time", I'm trying to figure out whetehr/how somethign analagous to a "valve" can be applied to the capacitor so that the energy is only allowed out slowly, rather than pouring out all at once.

THat probably sounds woefully ignorant, and I still have a very long way to gho in my learning, but I still think tht the "capacitor rather than battery" idea is just too *nifty keen* <LOL!> to ignore ;) And I think it'd be just soooooo cool if I could actually pull any of this off <L!>


I don't know much about super caps but I've heard that many of them also have a tendency not to last forever. To get the most energy from them you'll need a switcher that can almost squeeze the last electrons out even if the voltage dips below a volt. It also avoids the power waste of any linear circuit.

Also, many super caps are meant for low current RAM backup, meaning the Ri is way too high for any serious other use.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
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