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From: Erik Johansson <lirc@er...> - 2004-04-04 21:45:21
Together with a friend I'm trying to build a serial ir receiver and
transmitter that doesn't need external power. Unfortunely the circuit 
that we have constructed doesn't work. It works when we use external power,
but without it, we only get 3,6 V between RTS and ground. This is not enough
since the voltage drops about 1,7 V over the 78L05 and the receiver needs at
least 4,5 V to work. Without the circuit we get 12 V at RTS.
With the circuit connected we measured the current coming from RTS to 17 mA.
To us this doesn't seem like much, shouldn't the serial port be able to
So now we're wondering if anyone here knows if it's even possible to supply
the circuit without external power? If so, what have we done wrong? Maybe
someone has a working circuit we can take a look at?
We're grateful for any help we can get.
Thanks for making lirc, can't wait to start using it without external power ;)
(using 0.7pre3 now).
 - http://www.lysator.liu.se/~erre/img/ir.png
Nice joke Scotty, now beam my clothes up ...
Erik Johansson <lirc@...>