Placing different LEDs in parallel is always a bad idea.  Due to the
differing foward voltages, only one LED (the one with the lowest foward
voltage) will light.  In your case I would have expected either the LED or
the opto to work, but probably not both.

If you wish both to work, each LED should have it's own current limiting
resistor, assuming the driver can supply enough current to supply both LEDs.

Regards

Mike

> -----Original Message-----
> From: Graham North [SMTP:graham.north@LANDINST.COM]
> Sent: Thursday, August 31, 2000 10:50 AM
> To:   PICLIST@MITVMA.MIT.EDU
> 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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