Looking for BIG capacitors.

[James Knott]

Colin McGregor wrote:
> 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).
>
>   
So, why not use a battery?


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