Looking for BIG capacitors.

[Colin McGregor]

--- Kareem Shehata <kareem-d+8TeBu5bOew5LPnMra/2Q at public.gmane.org> wrote:
> On Wed, 2007-07-04 at 14:19 -0400, Colin McGregor
> wrote:
> 
> > I am looking to clear an old electronic project
> that I
> > started a while back and then never got finished.
> The
> > problem was the design I was following calls for a
> > 0.33 F  capacitor (yes, 0.33 F or a 330,000 uF
> cap.,
> > which is HUGE). Fortunately the highest voltage
> this
> > capacitor should have to take is 5 volts, so it
> > doesn't have to be a very high voltage capacitor,
> just
> > high capacitance. I have not been able to source
> such
> > big capacitor locally, I have tried the usual
> places
> > (Active Surplus, Active Components, Electrosonic,
> > Sayel, Above All) with no luck.
> > 
> > Anyone know of a place locally that sells HIGH
> value
> > capacitors? Or am a looking at the mail order
> route?
> 
> 
> Very surprised active surplus didn't have anything,
> but they're stock
> changes all the time.  Sayal sometimes has good
> stuff, otherwise you're
> best bet is something on the internet.
> 
> BTW:  What in the world are you looking to store
> that much charge for?
> Audio application or power conversion of some sort?

Comes back to my on-going love/hate relationship with
MythTV (great program but a TOTAL resource PIG!).
Anyway what I want is an infrared transciever, so the
MythTV box can both understand an IR remote, and can
control other IR devices (like cable box, and VCR).
The receiver part is painless, there are good, easy to
build IR receivers plans available (I wrote about one
for linuxjournal.com :-) ), the transmitter is the
problem. How do you provide power to light the IR LED?
Well, the conventional answers are:

- You don't really, basically you just put in an IR
LED and a resistor on the serial port. Works, but you
get an IR transmit range measured in inches.

- You connect the transmitter up to a wall tumour
style transformer and power the IR LED that way.

Neither of the above is ideal. Then I ran across a
design that uses a high capacity capacitor as a
battery. The serial port is always trickle charging
the capacitor, and the IR LED gets its power off the
capacitor. As long as you don't go for high duty
cycles the IR LED should have a range in tens of feet.

So, long range, and just one (serial) cable from PC to
IR box. Only downside is one pain in the butt part to
source (plus the previously noted smaller problem of
looking for a really nice looking way to package the
final result).

> Good luck!

Thanks.

> -kms
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