Opto-coupler failure question (HCNR201)

[Richard Rasker]

Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated linear
signal transfer application. I have about two dozen of these in a not
completely unimportant application aboard sea ships, in a rather hostile
environment: the machine room, with heat (>40 degrees centigrade),
vibration and moisture. For these reasons, I designed the whole thing to be
very, very robust, and for a year or so, all was fine.

Recently, however, I got a complaint that one of those devices had failed,
and a bit of research showed that the opto-isolator was the cause: from the
outside, the LED still behaves like a LED diode, but none of the two photo
diodes produce any output -- which strongly suggests that the LED doesn't
produce any IR output any more.

Now I'm a bit puzzled by this, as the whole input circuitry is designed in
such a way that the opto-isolator LED would be among one of the very last
components to break down in case of a voltage spike or such -- there are
zener diodes, low-ohm SMD resistors and an SMD opamp which would blow
first, and under no conditions, should the total LED current be able to
exceed 15mA (with 40mA absolute maximum rating). Destructive testing with a
circuit here confirmed this: I managed to blow up a handful of parts --
twice -- but never the opto-isolator. Overvoltage, reverse voltage -- it's
all handled the way I designed it.

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)?

Thanks in advance, best regards,

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

 

[Joerg]

Richard Rasker wrote:

Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated linear
signal transfer application. I have about two dozen of these in a not
completely unimportant application aboard sea ships, in a rather hostile
environment: the machine room, with heat (>40 degrees centigrade),
vibration and moisture. For these reasons, I designed the whole thing to be
very, very robust, and for a year or so, all was fine.

Recently, however, I got a complaint that one of those devices had failed,
and a bit of research showed that the opto-isolator was the cause: from the
outside, the LED still behaves like a LED diode, but none of the two photo
diodes produce any output -- which strongly suggests that the LED doesn't
produce any IR output any more.

Now I'm a bit puzzled by this, as the whole input circuitry is designed in
such a way that the opto-isolator LED would be among one of the very last
components to break down in case of a voltage spike or such -- there are
zener diodes, low-ohm SMD resistors and an SMD opamp which would blow
first, and under no conditions, should the total LED current be able to
exceed 15mA (with 40mA absolute maximum rating). Destructive testing with a
circuit here confirmed this: I managed to blow up a handful of parts --
twice -- but never the opto-isolator. Overvoltage, reverse voltage -- it's
all handled the way I designed it.

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)?

Both LED and photodiodes can die upon rather small reverse voltage
spikes. Without seeing your circuit it's hard to say which one is
vulnerable. I also don't know abs max because this miserable Acrobat
Reader crashed on that particular datasheet when scrolling.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Jan Panteltje]

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard Rasker
<spamtrap@linetec.nl> wrote in
<4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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?

 

[propman]

Joerg wrote:

Richard Rasker wrote:
Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated
linear
signal transfer application. I have about two dozen of these in a not
completely unimportant application aboard sea ships, in a rather hostile
environment: the machine room, with heat (>40 degrees centigrade),
vibration and moisture. For these reasons, I designed the whole thing
to be
very, very robust, and for a year or so, all was fine.

Recently, however, I got a complaint that one of those devices had
failed,
and a bit of research showed that the opto-isolator was the cause:
from the
outside, the LED still behaves like a LED diode, but none of the two
photo
diodes produce any output -- which strongly suggests that the LED doesn't
produce any IR output any more.

Now I'm a bit puzzled by this, as the whole input circuitry is
designed in
such a way that the opto-isolator LED would be among one of the very last
components to break down in case of a voltage spike or such -- there are
zener diodes, low-ohm SMD resistors and an SMD opamp which would blow
first, and under no conditions, should the total LED current be able to
exceed 15mA (with 40mA absolute maximum rating). Destructive testing
with a
circuit here confirmed this: I managed to blow up a handful of parts --
twice -- but never the opto-isolator. Overvoltage, reverse voltage --
it's
all handled the way I designed it.

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)?


Both LED and photodiodes can die upon rather small reverse voltage
spikes. Without seeing your circuit it's hard to say which one is
vulnerable. I also don't know abs max because this miserable Acrobat
Reader crashed on that particular datasheet when scrolling.

FWIW, this datasheet for the HCNR201:

http://www.datasheetcatalog.com/datasheets_pdf/H/C/N/R/HCNR201.shtml

......displays fine with Foxit Reader(freebie PDF reader that takes less
resources etc than Adobe Acrobat):

http://www.foxitsoftware.com/downloads/index.php

 

[Richard Rasker]

Joerg wrote:

Richard Rasker wrote:
Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated
linear signal transfer application.

....

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)?


Both LED and photodiodes can die upon rather small reverse voltage
spikes. Without seeing your circuit it's hard to say which one is
vulnerable. I also don't know abs max because this miserable Acrobat
Reader crashed on that particular datasheet when scrolling.

(I use xpfd; works very fast, never crashes)

The circuit is based on Figure 15A (page 11) of the datasheet
(a loop-powered receiver).
In my case, D1 is a 3.3V zener diode, R1 is 10K, and R3 is 10R.
Also, there's a 100R resistor in series with the LED, and a 4.7V zener diode
across +Iin and -Iin, plus a small cap (0.1uF) parallell to D1 and PD1.

So any reverse voltage across the input is always kept below 1V, and in case
of severe spikes, the zener diodes and caps should (and do) limit voltages
to below 3.3 volts. In forward mode, with feedback from PD1 shorted out,
the forward LED current maxes out at 15mA. Any increase in input
current/voltage results in first frying the 10R resistor, then shorting out
the 4.7V zener.

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

 

[Richard Rasker]

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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
--
http://www.linetec.nl

 

[Spehro Pefhany]

On Wed, 09 Sep 2009 20:02:38 +0200, Richard Rasker
<spamtrap@linetec.nl> wrote:

Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated linear
signal transfer application. I have about two dozen of these in a not
completely unimportant application aboard sea ships, in a rather hostile
environment: the machine room, with heat (>40 degrees centigrade),
vibration and moisture. For these reasons, I designed the whole thing to be
very, very robust, and for a year or so, all was fine.

Recently, however, I got a complaint that one of those devices had failed,
and a bit of research showed that the opto-isolator was the cause: from the
outside, the LED still behaves like a LED diode, but none of the two photo
diodes produce any output -- which strongly suggests that the LED doesn't
produce any IR output any more.

Now I'm a bit puzzled by this, as the whole input circuitry is designed in
such a way that the opto-isolator LED would be among one of the very last
components to break down in case of a voltage spike or such -- there are
zener diodes, low-ohm SMD resistors and an SMD opamp which would blow
first, and under no conditions, should the total LED current be able to
exceed 15mA (with 40mA absolute maximum rating). Destructive testing with a
circuit here confirmed this: I managed to blow up a handful of parts --
twice -- but never the opto-isolator. Overvoltage, reverse voltage -- it's
all handled the way I designed it.

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)?

Thanks in advance, best regards,

Richard Rasker

When you say that the LED behaves like an LED diode, you mean that Vf
is just what you'd expect from figure 9 of the datasheet? Is the
reverse leakage close to typical values?

40mA is allowed for a maximum of 50ns (!).

Might just be bad luck.. but as someone else suggested, this sounds
like mechanical damage of some kind to me if the diode appears
electrically sound. No deliberate modification of the package such as
bending of leads? Could the package be cracked
at the leadframe or elsewhere due to inadequate support of the PCB?

 

[Joerg]

Richard Rasker wrote:

Joerg wrote:

Richard Rasker wrote:
Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated
linear signal transfer application.

...

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)?

Both LED and photodiodes can die upon rather small reverse voltage
spikes. Without seeing your circuit it's hard to say which one is
vulnerable. I also don't know abs max because this miserable Acrobat
Reader crashed on that particular datasheet when scrolling.

(I use xpfd; works very fast, never crashes)

Yeah, I have to get something better than this dreaded Adobe stuff.
Foxit doesn't work with all docs but maybe xpdf does.

The circuit is based on Figure 15A (page 11) of the datasheet
(a loop-powered receiver).
In my case, D1 is a 3.3V zener diode, R1 is 10K, and R3 is 10R.
Also, there's a 100R resistor in series with the LED, ...

I was going to say, the figure 15 schematic is pretty hokey there. A
recipe for ... phut ... *POOF*.

... and a 4.7V zener diode
across +Iin and -Iin, plus a small cap (0.1uF) parallell to D1 and PD1.

So any reverse voltage across the input is always kept below 1V, and in case
of severe spikes, the zener diodes and caps should (and do) limit voltages
to below 3.3 volts. In forward mode, with feedback from PD1 shorted out,
the forward LED current maxes out at 15mA. Any increase in input
current/voltage results in first frying the 10R resistor, then shorting out
the 4.7V zener.

That all sounds quite diligent and robust. If the layout is of same
quality the failures are probably more in the category of bad luck, or a
bad batch of devices although I have never had that happen with HP/Avago
in over 20 years.

Thanks to Propman, for posting a working link.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Spehro Pefhany]

On Wed, 09 Sep 2009 20:55:49 +0200, Richard Rasker
<spamtrap@linetec.nl> wrote:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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

It's incredibly likely compared to what seems to be the only
alternative- an LED which acts exactly like a AlGaAs D but doesn't LE.

OTOH, an electrically damaged diode that measured something like a
short would not be unusual at all. Could be something like lightning
or RF damage. You don't have the opto in there because it's a benign
environment, eh?

 

[John Fields]

On Wed, 09 Sep 2009 20:02:38 +0200, Richard Rasker <spamtrap@linetec.nl>
wrote:

Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated linear
signal transfer application. I have about two dozen of these in a not
completely unimportant application aboard sea ships, in a rather hostile
environment: the machine room, with heat (>40 degrees centigrade),
vibration and moisture. For these reasons, I designed the whole thing to be
very, very robust, and for a year or so, all was fine.

Recently, however, I got a complaint that one of those devices had failed,
and a bit of research showed that the opto-isolator was the cause: from the
outside, the LED still behaves like a LED diode, but none of the two photo
diodes produce any output -- which strongly suggests that the LED doesn't
produce any IR output any more.

Now I'm a bit puzzled by this, as the whole input circuitry is designed in
such a way that the opto-isolator LED would be among one of the very last
components to break down in case of a voltage spike or such -- there are
zener diodes, low-ohm SMD resistors and an SMD opamp which would blow
first, and under no conditions, should the total LED current be able to
exceed 15mA (with 40mA absolute maximum rating). Destructive testing with a
circuit here confirmed this: I managed to blow up a handful of parts --
twice -- but never the opto-isolator. Overvoltage, reverse voltage -- it's
all handled the way I designed it.

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)?

---
I'd suspect the rather high ambient temp is taking its toll by reducing
the lifetime of the emitter.

 

[N_Cook]

Richard Rasker <spamtrap@linetec.nl> wrote in message
news:4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net...

Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated
linear
signal transfer application. I have about two dozen of these in a not
completely unimportant application aboard sea ships, in a rather hostile
environment: the machine room, with heat (>40 degrees centigrade),
vibration and moisture. For these reasons, I designed the whole thing to
be
very, very robust, and for a year or so, all was fine.

Recently, however, I got a complaint that one of those devices had failed,
and a bit of research showed that the opto-isolator was the cause: from
the
outside, the LED still behaves like a LED diode, but none of the two photo
diodes produce any output -- which strongly suggests that the LED doesn't
produce any IR output any more.

Now I'm a bit puzzled by this, as the whole input circuitry is designed in
such a way that the opto-isolator LED would be among one of the very last
components to break down in case of a voltage spike or such -- there are
zener diodes, low-ohm SMD resistors and an SMD opamp which would blow
first, and under no conditions, should the total LED current be able to
exceed 15mA (with 40mA absolute maximum rating). Destructive testing with
a
circuit here confirmed this: I managed to blow up a handful of parts --
twice -- but never the opto-isolator. Overvoltage, reverse voltage -- it's
all handled the way I designed it.

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)?

Thanks in advance, best regards,

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

I once had a failure in a HV isolation section of a scope, stored in a damp
environment. Cracking it open, mould had grown over the light tube causing
an electrically conductive path between both sides. If mould grew on the
face of the light guide it would block the light. Opto-isolator was
otherwise sealed , but only to non-military spec.
Try cracking one open one and look under a microscope for petri-dish-like
mould spots

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

 

[nesesu]

On Sep 9, 11:02 am, Richard Rasker <spamt...@linetec.nl> wrote:

Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated linear
signal transfer application. I have about two dozen of these in a not
completely unimportant application aboard sea ships, in a rather hostile
environment: the machine room, with heat (>40 degrees centigrade),
vibration and moisture. For these reasons, I designed the whole thing to be
very, very robust, and for a year or so, all was fine.

Recently, however, I got a complaint that one of those devices had failed,
and a bit of research showed that the opto-isolator was the cause: from the
outside, the LED still behaves like a LED diode, but none of the two photo
diodes produce any output -- which strongly suggests that the LED doesn't
produce any IR output any more.

Now I'm a bit puzzled by this, as the whole input circuitry is designed in
such a way that the opto-isolator LED would be among one of the very last
components to break down in case of a voltage spike or such -- there are
zener diodes, low-ohm SMD resistors and an SMD opamp which would blow
first, and under no conditions, should the total LED current be able to
exceed 15mA (with 40mA absolute maximum rating). Destructive testing with a
circuit here confirmed this: I managed to blow up a handful of parts --
twice -- but never the opto-isolator. Overvoltage, reverse voltage -- it's
all handled the way I designed it.

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)?

Thanks in advance, best regards,

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

FWIW, many years ago were designed a high voltage control system that
needed 6000V isolation between the controller and the controlled
circuit. the intended environmental conditions were similar,
especially the high vibration. We chose the GE H11A1 optocoupler since
it was one of only a few at that time that was rated for 6000V
standoff. The system worked as designed but under a lengthy series of
environmental tests, we began to see failures of the optocouplers.
That was traced to a drastic reduction of the 'current transfer ratio'
of the device and by slicing several new and failed devices we were
able to track it down to the emitter which, as in your case, looked
normal electrically, but had much reduced IR emission [as low as 1% of
new]. It was finally determined as a process issue at GE and later
'improved' batches did not display such behaviour. The system was
released and worked well for many years with a low failure rate.

Neil S.

 

[Jan Panteltje]

On a sunny day (Wed, 09 Sep 2009 20:55:49 +0200) it happened Richard Rasker
<spamtrap@linetec.nl> wrote in
<4aa7fa35$0$725$7ade8c0d@textreader.nntp.internl.net>:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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.

 

[Richard Rasker]

Joerg wrote:

Richard Rasker wrote:
Joerg wrote:

Richard Rasker wrote:
Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated
linear signal transfer application.

...

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)?

Both LED and photodiodes can die upon rather small reverse voltage
spikes. Without seeing your circuit it's hard to say which one is
vulnerable. I also don't know abs max because this miserable Acrobat
Reader crashed on that particular datasheet when scrolling.

(I use xpfd; works very fast, never crashes)


Yeah, I have to get something better than this dreaded Adobe stuff.
Foxit doesn't work with all docs but maybe xpdf does.

Um, I'm afraid xpdf is of little or no use to you -- it's Linux only, and
from your reference to Foxit I surmise you're running Windows.

The circuit is based on Figure 15A (page 11) of the datasheet
(a loop-powered receiver).
In my case, D1 is a 3.3V zener diode, R1 is 10K, and R3 is 10R.
Also, there's a 100R resistor in series with the LED, ...


I was going to say, the figure 15 schematic is pretty hokey there. A
recipe for ... phut ... *POOF*.

No, in have about double the number of components in the primary circuit as
the example in Fig. 15A -- and almost all extra components are safeguards
and the likes.

... and a 4.7V zener diode
across +Iin and -Iin, plus a small cap (0.1uF) parallell to D1 and PD1.

So any reverse voltage across the input is always kept below 1V, and in
case of severe spikes, the zener diodes and caps should (and do) limit
voltages to below 3.3 volts. In forward mode, with feedback from PD1
shorted out, the forward LED current maxes out at 15mA. Any increase in
input current/voltage results in first frying the 10R resistor, then
shorting out the 4.7V zener.


That all sounds quite diligent and robust. If the layout is of same
quality the failures are probably more in the category of bad luck, or a
bad batch of devices although I have never had that happen with HP/Avago
in over 20 years.

Thanks to Propman, for posting a working link.

I usually have good experiences with those optical devices as well -- that's
also why I'm still a bit puzzled.

But anyway, thanks for you reaction.

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

 

[Richard Rasker]

Spehro Pefhany wrote:

On Wed, 09 Sep 2009 20:02:38 +0200, Richard Rasker
spamtrap@linetec.nl> wrote:

Hi all,

I'm using an HCNR201 opto-isolator device in a galvanically isolated
linear signal transfer application.

[snip mysterious breakdown]

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)?

When you say that the LED behaves like an LED diode, you mean that Vf
is just what you'd expect from figure 9 of the datasheet?

Hmm, I get a Vf of 1.3V @ 10mA If, so that's rather low, but still just
within specifications.

Is the reverse leakage close to typical values?

I don't know what typical valueas are, but at Vr = 1V, I got about 1uA of
leakage current, rising rapidly with higher reverse voltage. At Vr = 3
volts and up, the LED starts conducting whole milli-amps (current-limited
to 2mA) -- so I guess that if the LED wasn't broken to begin with, it is
now.
But during all this, I monitored both photo diodes, and at no point did they
produce any sigificant voltage into 10MOhm voltmeter inputs.

40mA is allowed for a maximum of 50ns (!).

I know, and 20mA max is recommended. But as I said, the current is limited
to some 15mA in several different ways. Under normal operating conditions
(i.e. with working feedback circuitry), it can't exceed 5mA. And the rest
of the original circuit is fine -- I stuck in another HCNR201, and it
worked perfectly right away. So no other components have failed, at least
not in any permanent manner.

Might just be bad luck.. but as someone else suggested, this sounds
like mechanical damage of some kind to me if the diode appears
electrically sound. No deliberate modification of the package such as
bending of leads?

Nope, I just bent the legs slightly inwards for normal assembly, as is usual
with DIP cases. And I'm pretty certain that I didn't overheat it either
during soldering.

Could the package be cracked at the leadframe or elsewhere due to
inadequate support of the PCB?

The PCB is quite small (5x8cm, or 2x3 inches approx.) and very well
supported. Also, the opto-isolator case doesn't show any cracks or other
damage.
But I guess I'll try to crack it open, although I seriously doubt if I can
find anything -- if only because cracking it open will certainly disturb
anything blocking the light path anyway.

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

 

[Richard Rasker]

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:55:49 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7fa35$0$725$7ade8c0d@textreader.nntp.internl.net>:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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

 

[Richard Rasker]

Spehro Pefhany wrote:

On Wed, 09 Sep 2009 20:55:49 +0200, Richard Rasker
spamtrap@linetec.nl> wrote:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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

It's incredibly likely compared to what seems to be the only
alternative- an LED which acts exactly like a AlGaAs D but doesn't LE.

OTOH, an electrically damaged diode that measured something like a
short would not be unusual at all. Could be something like lightning
or RF damage. You don't have the opto in there because it's a benign
environment, eh?

Hehe, spot on -- this is a 24V ship's electrical installation, with heavy DC
motors and other possible sources of interference. That's why I also use
DC-DC-couplers (with a wide-range input) to supply the rest of the
circuitry. That way, input, output and supply are all galvanically
separated.
But the LED still behaves as a LED -- in an electrical sense, that is. It's
not shorted out or anything.

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

 

[Joerg]

Richard Rasker wrote:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:55:49 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7fa35$0$725$7ade8c0d@textreader.nntp.internl.net>:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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.

Somehow sounds like a busted LED.

BTW, it's best not to split groups and follow-up fields differently, it
mangles your thread.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[John Fields]

On Thu, 10 Sep 2009 19:30:16 +0200, Richard Rasker <spamtrap@linetec.nl>
wrote:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:55:49 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7fa35$0$725$7ade8c0d@textreader.nntp.internl.net>:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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.

---
My guess would be that the high ambient temp in which the device works
has taken its toll on the LED.

 

[Richard Rasker]

Joerg wrote:

Richard Rasker wrote:
Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:55:49 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7fa35$0$725$7ade8c0d@textreader.nntp.internl.net>:

Jan Panteltje wrote:

On a sunny day (Wed, 09 Sep 2009 20:02:38 +0200) it happened Richard
Rasker <spamtrap@linetec.nl> wrote in
4aa7edbe$0$730$7ade8c0d@textreader.nntp.internl.net>:

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.


Somehow sounds like a busted LED.

BTW, it's best not to split groups and follow-up fields differently, it
mangles your thread.

Hm, I /did/ set the follow-up to sci.electronics.repair. I don't know what
went wrong ...

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