I think communicating and documenting stupid mistakes is more important
than communicating successes, so here I go again.

I use an IR LED and a TSOP receiver to let a board-under-test log
messages on an LCD without a galvanic connection. The board-under-test
uses the IR LED to send the message, of course modulated at the
frequency appropriate to the TSOP receiver (I use 36 KHz). To check
whether the pic-under-test does indeed 'blink' the IR LED I put a normal
(red) led parallel (both with their own series resistor).

I know the receiver with LCD screen is OK because I use that a lot. A
new board-under-test worked somewhat: only at very short distances: 1cm,
where 50cm is a more normal distance. 

Now what was wrong? I suspected that the red LED was loading the PIC
output so much that the IR led got nearly 0 current, so I removed the
series resistor of the red LED. Now the communication stopped totally!

A closer look revealed that the IR LED was wired backwards, so it was
not doing anything. The RED led seems to emit enough IR to make
communication at a very short distance possible. Wiring the IR LED
correctly of course make the setup work like it should.

Morale? Don't jump to conclusions, look at the facts. (if you want that
worded in another way read Pratchet)

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu
 

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist