Try placing LED in series instead of placing it in parallel to optocouple
and reduce series resistance.
Did you check if LED is removed optocouple works fine? It seems your
optocoupler's LED gone short circuited.
Irfan
----- Original Message -----
From: Graham North <graham.north@LANDINST.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, August 31, 2000 9:49 AM
Subject: [EE]: Pic driving Optocoupler & Led with same pin?


> Hi
>
> I currently have a few boards with pics driving triac driver optocouples.
>
> For fault finding purposes I thought it would be a good idea to put an
> ordinary Led in
> parallel with the optocouple.  However when I did this neither the led lit
> nor the optocouple
> triggered.
>
> Between the pic pin and the optocouple is a 330 ohm resistor.  I tried
> reducing this but it
> made no difference.
>
> If the optocouple is removed the Led lights fine.
>
> Any ideas?
>
> Regards
>
> Graham North
>
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