Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:55:49 +0200) it happened Richard
Rasker wrote in
et:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker wrote in
et:

So my question: is this a simple case of "bad luck", or are there other
ways a LED in an opto-isolator may fail in this weird way (current OK,
yet no light)?

Perhaps some part internal to the opto-isolater did break of due to
vibration and blocks the light path?
Did you open the defective one?

No, I didn't (yet) -- but isn't this very, very unlikely?

Richard Rasker

I could also imagine a bind wire coming lose of the photo transistor.
Before doing any destructive investigation, perhaps you could also check
the photo transistor.
Vbe and Vbc diodes, if it has the base on a pin, multimeter + on
collector, - on emittor, and feed the base from the collector via say 100k
Ohm. Should draw some current.

The HCNR201 isn't a normal opto-coupler; it doesn't have one photo
transistor, but two photo diodes, one of which is normally used in a
feedback circuit driving the LED. Both photo diodes behave the same, i.e.
they don't respond to any current I send through the LED.

Richard Rasker
--
http://www.linetec.nl