IR LED to repair remote control

[Andrew]

Unfortunately my Logitech harmony 880 remote stopped working. When
pointing it into a digital camera, I can no longer see the IR LEDs
lighting up (there are two). Logitech tech support has confirmed that
the IR LEDs are probably dead, but they have been less than helpful.

In an attempt to fix the remote myself, I bought two sets of IR
emitter/detector packs from radioshack (quick and easy), part number
276-142 (http://www.radioshack.com/product/index.jsp?
parentPage=search&summary=summary&cp=&productId=2049723&accessories=accessories&kw=ir
+diode&techSpecs=techSpecs&currentTab=features&custRatings=custRatings&sr=1&features=features&origkw=ir
+diode&support=support&tab=summary).

I used just the emitters (tinted package) and replaced both of the
emitters that were on the remote. The old emitters were clear
package, FWIW.

The remote worked great again after this for two days, but now, has
apparently died again. I suspect that there is either some other
problem with the board that is blowing the LEDs, or the radioshack
replacements were not within spec. I'm really hoping it is the LEDs
not within spec, because I don't want to deal with logitech tech
support any more. Or, since I'm conveniently out of warranty, shell
out for them to repair it, when seemingly I can repair it myself for a
few dollars.

I've never really worked with IR LEDs before, so I was wondering if I
could get a few pointers in trying to order some IR LEDs from
digikey. I realize it may be difficult without knowing the details of
the design of the remote. My plan, though, is to get the highest
rated LEDs and hope for the best.

The wavelength of the emitter that worked from radioshack was 940nm.
On digikey I see that there are LEDs ranging from 860nm to 950nm.
This is one area where I'm not clear. Just because the 940nm LED
worked (and worked really well on all my devices I might add, it was
not flaky at all), does that mean that I should stick with that
wavelength? Or is it likely that the other wavelengths are close
enough that they will also work well?

And what ratings should I pay particularly close attention to when
trying to spec an LED for this purpose? I'm thinking a combination of
the highest pulse forward current and highest continuous current? For
that purpose I saw the LITE-ON LTE-5228A, digikey part no 160-1062-
ND. 250mW power dissipation, 3A peak forward current, 150mA cont
current, 7.2V reverse voltage, and 940nm wavelength. It seems to be
the highest ratings in all categories for the 940nm wavelength LEDs
digikey stocks, and is my top choice right now. It also uses a clear
package like the original emitters, if that even matters.

Any thoughts overall on the matter?

 

[James Arthur]

Unfortunately my Logitech harmony 880 remote stopped working. When
pointing it into a digital camera, I can no longer see the IR LEDs
lighting up (there are two). Logitech tech support has confirmed that
the IR LEDs are probably dead, but they have been less than helpful.

[...] I bought [...] part number 276-142 [...]
The remote worked great [...] but [...] died again.
[...] I was wondering if I
could get a few pointers in trying to order some IR LEDs[...]
The wavelength of the emitter that worked from radioshack was 940nm.
On digikey I see that there are LEDs ranging from 860nm to 950nm.
[...] does that mean that I should stick with that
wavelength?[...]

And what ratings should I pay particularly close attention to when
trying to spec an LED for this purpose? I'm thinking a combination of
the highest pulse forward current and highest continuous current? For
that purpose I saw the LITE-ON LTE-5228A, digikey part no 160-1062-
ND. 250mW power dissipation, 3A peak forward current, 150mA cont
current, 7.2V reverse voltage, and 940nm wavelength. It seems to be
the highest ratings in all categories for the 940nm wavelength LEDs
digikey stocks, and is my top choice right now. It also uses a clear
package like the original emitters, if that even matters.

Any thoughts overall on the matter?

Measure it. Put a couple 1n4001 rectifiers in series with a 0.1 ohm
resistor, then operate the remote. View waveforms with an
oscilloscope.

Or just get DigiKey's hardiest IRLEDs (one of each wavelength),
salvage some LEDs from another cast-off remote.

Might help us to know if the failed LEDs failed open, shorted, etc.

Cheers,
James Arthur

 

[John Popelish]

Unfortunately my Logitech harmony 880 remote stopped working. When
pointing it into a digital camera, I can no longer see the IR LEDs
lighting up (there are two).

If you could ever see them light up, they were almost
certainly 880 nm LEDS, not 940 nm types. A few IR receivers
are also narrow band filtered for 880 nm sources.

(snip)

I used just the emitters (tinted package) and replaced both of the
emitters that were on the remote. The old emitters were clear
package, FWIW.

The filter serves no function in emitters, except for visual
identification. Some manufacturers tint 940 nm units but
put 880 nm units in clear packages (or vice versa), to
distinguish them. I don't know how standardized this
practice is.

The remote worked great again after this for two days, but now, has
apparently died again. (snip)

The wavelength of the emitter that worked from radioshack was 940nm.
On digikey I see that there are LEDs ranging from 860nm to 950nm.
This is one area where I'm not clear. Just because the 940nm LED
worked (and worked really well on all my devices I might add, it was
not flaky at all), does that mean that I should stick with that
wavelength? Or is it likely that the other wavelengths are close
enough that they will also work well?

Most receivers work with either wavelength. Only a few
based on narrow band gallium arsenide aluminide detectors
work only with the 880 nm types.
http://www.optodiode.com/pdf/SEN5249e.pdf

The great majority of receivers use silicon detectors with
long pass optical filters that block most visible
wavelengths that the silicon is also sensitive to.

And what ratings should I pay particularly close attention to when
trying to spec an LED for this purpose? I'm thinking a combination of
the highest pulse forward current and highest continuous current? For
that purpose I saw the LITE-ON LTE-5228A, digikey part no 160-1062-
ND. 250mW power dissipation, 3A peak forward current, 150mA cont
current, 7.2V reverse voltage, and 940nm wavelength. It seems to be
the highest ratings in all categories for the 940nm wavelength LEDs
digikey stocks, and is my top choice right now. It also uses a clear
package like the original emitters, if that even matters.

I don't think the package color matters, but high peak
current rating and high milliwatts per steradian output
intensity are good. Though, the highest intensity units are
also the narrowest beam width units, meaning you have to aim
them pretty accurately.

A good choice might be the TSAL6100 (950 nm) or its high
output cousins (assuming you can use the 5mm diameter package).
http://www.vishay.com/docs/81009/tsal6100.pdf
http://www.vishay.com/docs/81090/tsff5210.pdf

But if I was going to order something, I would get both 940
and 880 nm variations. If the control has more than one
emitter, I might use some of both.

 

[Andrew]

If you could ever see them light up, they were almost
certainly 880 nm LEDS, not 940 nm types. A few IR receivers
are also narrow band filtered for 880 nm sources.

I didn't look at the remote ever in the digital camera before hand,
but I tested another remote just to be sure I could see IR, and the
tech support were the people who asked me to try it to look for the IR
lighting up. I presume they expected me to see results this way. I
guess that means that at least one of the two transmitters was 880nm?

The filter serves no function in emitters, except for visual
identification. Some manufacturers tint 940 nm units but
put 880 nm units in clear packages (or vice versa), to
distinguish them. I don't know how standardized this
practice is.

From what I can tell, in the T 1 3/4 (5mm) package, which is what I

need, it seems that all the 940nm that digikey carries are clear
package. But that radioshack emitter at 940nm was tinted, and the
radioshack matching emitter was clear. Go figure?

Most receivers work with either wavelength. Only a few
based on narrow band gallium arsenide aluminide detectors
work only with the 880 nm types.http://www.optodiode.com/pdf/SEN5249e.pdf

The great majority of receivers use silicon detectors with
long pass optical filters that block most visible
wavelengths that the silicon is also sensitive to.

So it seems that a more "universal" wavelength of this purpose would
be 880nm?

A good choice might be the TSAL6100 (950 nm) or its high
output cousins (assuming you can use the 5mm diameter package).http://www.vishay.com/docs/81009/tsal6100.pdfhttp://www.vishay.com/docs/81090/tsff5210.pdf

It seems that the LITE-ON 940nm I listed has similar, if not a little
"better" specs in all categories than the 950nm TSAL6100? And a
little wider viewing angle to boot. Was there something about the
LITE-ON LTE-5228A that you didn't like? (http://rocky.digikey.com/
WebLib/Lite-on/Web%20Data/LTE-5228A.pdf).

But if I was going to order something, I would get both 940
and 880 nm variations. If the control has more than one
emitter, I might use some of both.

Yeah, there are two emitters, so I think I might try an 880 and a
940. Likely the 880 from Vishay and the 940 from lite-on.


As an additional question. Does anyone have any clue why these diodes
would both go out completely randomly in the original unit? It was
about a year and a half old, and I found a number of posts of the
exact same thing happening to other people after almost the same
amount of time. I could see one of the diodes going out, but both
simultaneously? Maybe they are connected in series? Or maybe one
went out and I never noticed, then the other went? I wouldn't mind
examining it a little further to find the root cause, or at least
hopefully the new diode I put in exceeds the original diode's
specifications such that the problem isn't repeated.

 

[John O'Flaherty]

I didn't look at the remote ever in the digital camera before hand,
but I tested another remote just to be sure I could see IR, and the
tech support were the people who asked me to try it to look for the IR
lighting up. I presume they expected me to see results this way. I
guess that means that at least one of the two transmitters was 880nm?


need, it seems that all the 940nm that digikey carries are clear
package. But that radioshack emitter at 940nm was tinted, and the
radioshack matching emitter was clear. Go figure?


So it seems that a more "universal" wavelength of this purpose would
be 880nm?


It seems that the LITE-ON 940nm I listed has similar, if not a little
"better" specs in all categories than the 950nm TSAL6100? And a
little wider viewing angle to boot. Was there something about the
LITE-ON LTE-5228A that you didn't like? (http://rocky.digikey.com/
WebLib/Lite-on/Web%20Data/LTE-5228A.pdf).


Yeah, there are two emitters, so I think I might try an 880 and a
940. Likely the 880 from Vishay and the 940 from lite-on.

As an additional question. Does anyone have any clue why these diodes
would both go out completely randomly in the original unit? It was
about a year and a half old, and I found a number of posts of the
exact same thing happening to other people after almost the same
amount of time. I could see one of the diodes going out, but both
simultaneously? Maybe they are connected in series? Or maybe one
went out and I never noticed, then the other went? I wouldn't mind
examining it a little further to find the root cause, or at least
hopefully the new diode I put in exceeds the original diode's
specifications such that the problem isn't repeated.

You could have an intermittent bad connection in the remote, which
would explain the replacements failing soon. You might check for
voltage with a meter, or preferably a scope, at the exact moment when
you know there is no light coming out.

 

[John Popelish]

I didn't look at the remote ever in the digital camera before hand,
but I tested another remote just to be sure I could see IR, and the
tech support were the people who asked me to try it to look for the IR
lighting up. I presume they expected me to see results this way. I
guess that means that at least one of the two transmitters was 880nm?

880 nm LEDs give off a faint bit of visible red light. If
you look into the LED in total darkness you will see a faint
red glow, if the LED is on long enough for your eye to
respond. 940/950 nm LEDs are generally totally invisible to
the eye.

need, it seems that all the 940nm that digikey carries are clear
package. But that radioshack emitter at 940nm was tinted, and the
radioshack matching emitter was clear. Go figure?



So it seems that a more "universal" wavelength of this purpose would
be 880nm?

I think so.

It seems that the LITE-ON 940nm I listed has similar, if not a little
"better" specs in all categories than the 950nm TSAL6100? And a
little wider viewing angle to boot. Was there something about the
LITE-ON LTE-5228A that you didn't like? (http://rocky.digikey.com/
WebLib/Lite-on/Web%20Data/LTE-5228A.pdf).


Yeah, there are two emitters, so I think I might try an 880 and a
940. Likely the 880 from Vishay and the 940 from lite-on.


As an additional question. Does anyone have any clue why these diodes
would both go out completely randomly in the original unit?

An overload is the only reason they should fail. Their
driver may have failed and put DC across them, instead of a
train of pulses.

It was
about a year and a half old, and I found a number of posts of the
exact same thing happening to other people after almost the same
amount of time. I could see one of the diodes going out, but both
simultaneously? Maybe they are connected in series?

Quite likely. Their normal voltage drop is about 1.4 volts,
so a two cell supply will drive two of them with little
current regulation.

Or maybe one
went out and I never noticed, then the other went? I wouldn't mind
examining it a little further to find the root cause, or at least
hopefully the new diode I put in exceeds the original diode's
specifications such that the problem isn't repeated.

The failed LEDs should show either a low resistance in both
directions, or some leakage in the reverse direction and
normal drop (about 1.2 to volts with1 mA forward bias) with
a diode check function.

 

[Andrew]

You could have an intermittent bad connection in the remote, which
would explain the replacements failing soon. You might check for
voltage with a meter, or preferably a scope, at the exact moment when
you know there is no light coming out.

Yes, I intend to take a peek when I get home. The g/f says it was
broken again so I need to confirm and investigate further. From a
light visual inspection the first time, there was nothing I could see
wrong, and I know the solder joints were good both times. I'm going
to poke around when I get home, though.

I'm not sure it is an *intermittent* connection because I beat it up
pretty good looking for a bad connection and it didn't work (I know,
bad idea) even for a split second during the beating it up phase. But
gently replacing the LEDs made it work. Last night, with the radio
shack replacements, it was working great. My g/f turned on a DVD, put
the remote on the table and fell asleep, and first thing in the
morning, it wasn't working.

 

[Andrew]

880 nm LEDs give off a faint bit of visible red light. If
you look into the LED in total darkness you will see a faint
red glow, if the LED is on long enough for your eye to
respond. 940/950 nm LEDs are generally totally invisible to
the eye.

I never did notice a red light from the remote. I had thought the
reason that they have you use a digital camera is because the sensor
can pick up a light range that your eye cannot. Are you sure the
digital camera can't pick up 940nm? You might try it if you never
have. It was pretty cool Aim a remote at your camera and watch in
the viewfinder for a purple light.

An overload is the only reason they should fail. Their
driver may have failed and put DC across them, instead of a
train of pulses.

That's what I was afraid of. If it were the driver, would you imagine
it would "die" instantly, never to work agian, or would you suspect
that the driver could have an intermittent problem that may kill
diodes daily or weekly as it "dies" slowly? If it were more a "dies"
slowly scenario, then replacing LEDs may not do the trick. If perhaps
the LEDs were slightly overloaded from the driver from the factory (by
a poor design), then I suppose it is possible that they did not last
as long as anticipated because they were run at or just over their
maximum ratings for a long period of time. In this case, I would
suspect a higher rated diode may correct the problem.

Quite likely. Their normal voltage drop is about 1.4 volts,
so a two cell supply will drive two of them with little
current regulation.

Yes, another reason I suspected them to be in series was because I
replaced one of the diodes at first to see if it would fix the problem
before I opened the second package, and it did not work. I then tried
replacing the second diode, and it worked. This led me to believe it
was in series, or there was something else fishy going on, but I was
so happy it worked again, I sorta forgot about it

The failed LEDs should show either a low resistance in both
directions, or some leakage in the reverse direction and
normal drop (about 1.2 to volts with1 mA forward bias) with
a diode check function.- Hide quoted text -

Yeah, I'll have to inspect the diodes to see how they failed. I'll
also poke around a little more while I'm in there to see what else I
can see.



Thanks for your help everyone!

 

[John Popelish]

I never did notice a red light from the remote. I had thought the
reason that they have you use a digital camera is because the sensor
can pick up a light range that your eye cannot. Are you sure the
digital camera can't pick up 940nm? You might try it if you never
have. It was pretty cool Aim a remote at your camera and watch in
the viewfinder for a purple light.

Most digital cameras will respond at least a little to
either wavelength, but more strongly to the 880 nm.

That's what I was afraid of. If it were the driver, would you imagine
it would "die" instantly, never to work agian, or would you suspect
that the driver could have an intermittent problem that may kill
diodes daily or weekly as it "dies" slowly?

Honestly, I would expect it to never work again, if the
driver failed. The fact that you restored operation, for a
little while, with new LEDs, sounds like you just need
beefier ones.

 

[Don Klipstein]

Unfortunately my Logitech harmony 880 remote stopped working. When
pointing it into a digital camera, I can no longer see the IR LEDs
lighting up (there are two). Logitech tech support has confirmed that
the IR LEDs are probably dead, but they have been less than helpful.

In an attempt to fix the remote myself, I bought two sets of IR
emitter/detector packs from radioshack (quick and easy), part number
276-142 (http://www.radioshack.com/product/index.jsp?
parentPage=search&summary=summary&cp=&productId=2049723&accessories=accessories&kw=ir
+diode&techSpecs=techSpecs&currentTab=features&custRatings=custRatings&sr=1&features=features&origkw=ir
+diode&support=support&tab=summary).

I used just the emitters (tinted package) and replaced both of the
emitters that were on the remote. The old emitters were clear
package, FWIW.

The remote worked great again after this for two days, but now, has
apparently died again. I suspect that there is either some other
problem with the board that is blowing the LEDs, or the radioshack
replacements were not within spec. I'm really hoping it is the LEDs
not within spec, because I don't want to deal with logitech tech
support any more. Or, since I'm conveniently out of warranty, shell
out for them to repair it, when seemingly I can repair it myself for a
few dollars.

I've never really worked with IR LEDs before, so I was wondering if I
could get a few pointers in trying to order some IR LEDs from
digikey. I realize it may be difficult without knowing the details of
the design of the remote. My plan, though, is to get the highest
rated LEDs and hope for the best.

The wavelength of the emitter that worked from radioshack was 940nm.
On digikey I see that there are LEDs ranging from 860nm to 950nm.
This is one area where I'm not clear. Just because the 940nm LED
worked (and worked really well on all my devices I might add, it was
not flaky at all), does that mean that I should stick with that
wavelength? Or is it likely that the other wavelengths are close
enough that they will also work well?

And what ratings should I pay particularly close attention to when
trying to spec an LED for this purpose? I'm thinking a combination of
the highest pulse forward current and highest continuous current? For
that purpose I saw the LITE-ON LTE-5228A, digikey part no 160-1062-
ND. 250mW power dissipation, 3A peak forward current, 150mA cont
current, 7.2V reverse voltage, and 940nm wavelength. It seems to be
the highest ratings in all categories for the 940nm wavelength LEDs
digikey stocks, and is my top choice right now. It also uses a clear
package like the original emitters, if that even matters.

Any thoughts overall on the matter?

I expect wavelength anywhere from 860 to 950 nm to be OK.

I think better would be LEDs with higher current capability, both
continuous and peak.

Then again, I see enough inconsistincies between LED datasheets and
actual performance...
If the unit is indeed out of warranty, one thing I would do is add a
resistor in series with each LED. Go ahead, splice resistors in, do a bit
of surgery/hacking if the unit is out of warranty!
I think that a 10 ohm resistor in series with each LED should make a
difference - by dropping half a volt at 50 mA. 1/8 watt resistors should
be adequate and are very compact.

The above Lite-On LED does have a datasheet making a claim for higher
current and power. I give some fair chance this is true and likely to
help.
But beware, it has a wider beam width (35 degrees), and that can detract
from the beam intensity and reduce your range - especially if you need
resistors to keep eve these from blowing.
Should you need resistors, go for higher mW/sr intensity LEDs (they tend
to have narrower beams) and be prepared to use 15 possibly 22 ohm
resistors to keep the LEDs from blowing.

==============================================

By any chance, are you using lithium batteries instead of alkalines?
The extra .1 or so volt per cell could make a difference if the product
design is not tolerant of that extra voltage.

==============================================

You may do well by using rechargeable batteries (NiMH or NiCd) - the
voltage is a little less than that of fresh alkalines - that may save your
LEDs.

=====================================

- Don Klipstein ([email protected])

 

[Don Klipstein]

I never did notice a red light from the remote. I had thought the
reason that they have you use a digital camera is because the sensor
can pick up a light range that your eye cannot. Are you sure the
digital camera can't pick up 940nm?

It appears to me that in general, digital cameras have some ability to
"see" the "glow" of 940-950 nm LEDs. They do indeed, as mentioned,
usually appear purplish, often a shade close to "lavendar".
However, 880 nm ones show up with a similar, maybe slightly different
color (still usually purplish/"lavendar") to digital cameras.

- Don ([email protected])

 

[Hammy]

snip

I just built a dual beam IR Tx/Rcv using the TSAL6100 and Panasonic
detector. If you don't have a scope you will be limited in determining
any problems.

One thing you can check with a DVM is the DC voltage that is applied
to the drive circuit. If you can determine the regulator then verify
with a DVM it's regulating properly. If it's a low dropout type and
it's failed this might explain why it works for a while after you
change the LED's. All components have probably been derated for at
least an ambient temp of 50 deg C. So if an extra 0.3V to 1V is
applied to the circuit it won't immediately be destructive. Depending
on the duty-cycle it may even be able to take substantially more
voltage (standard three terminal regulators) 2-5V for a time. I
designed mine for max range and 60 deg C ambient and they could
survive an extra three volts for a minute or so (this is continuous
use 10% overall duty cycle).The extra voltage drops across the current
limiting resistor, in my case almost doubling the current, and the
power dissipation in the LED's.

The TSAL6100 has a Radiant Intensity = 80mW/sr min - 130 typ mW/sr @
0.1A,and 650mW/sr min - 1000 typ mW/sr at 1A.

Versus the 18 to 37 mW/sr at 0.1A for the LTE-5228A.

And yes a digital camera can see IR at 940nm. I used it to align my
TX/Rcv.

If you can get the model of detector for your remote you want to match
the emitter wavelength to the detector for max sensitivity.

 

[Ira]

Andrew, I have the same problem with my 880 Harmony, it happened
Tuesday afternoon (Sept 25th). Everything on the LCD screen looks
normal, but my devices don't respond to the remote. I took it apart
and measured about 1.6v on the diode with a digital multi meter. I
also concluded that the diodes were bad.
One thing I have to add to the disscussion is that a couple of days
ago I noticed that the IR shield was very warm, the only source of the
heat was the IR diodes. The remote was sitting flat and nothing was
hitting any buttons, but I was a little freaked out, so imediately I
pulled out the battery. I rebooted the remote, and everything worked
fine for a couple of days. Untill it stoped working...boo.
I sent a letter to Logitech customer service, but it seems like they
might not be too helpful, I asked for the diode specs, but that's
really just wishfull thinking. Let me know how some beefier diodes
hold-up and I'll keep you advised of anything I find.

 

[whit3rd]

Unfortunately my Logitech harmony 880 remote stopped working.
In an attempt to fix the remote myself, I bought two sets of IR
emitter/detector packs from radioshack

[and another Harmony user has a remote that almost works, but low/no
output]

As you suspect, the peak current rating for the remote may be higher
than the Radio Shack LEDs; the replacement pair could have failed
due to overcurrent.

I've seen a weak battery kill a remote that functioned fine (used
under
1 mA to run the smarts) until a command was sent (using 100 mA to run
the LED). Always try replacing the batteries first.

Because you have the phototransistors, you can make a simple
integrating detector
to calibrate the remote output. Use a shoebox, with a hole in the
leftside to shine
your remote in, a hole in the right side with the phototransistor, and
a separator
in the middle of the box (tape in a card, with a small hole in the
center, to leak
light from the illuminator side to the detector side). You'll need to
use a pullup/pulldown
resistor pair to bias the phototransistor from (for instance) a 5V
supply.
I'd use a couple of 1k ohm resistors. If the signal (into an AC
voltmeter
or oscilloscope) from a known-good remote control is 0.5V, you're
sensitive enough. Change the hole in the separator card to change the
sensitivity.

It's easier to find unneeded remotes than to buy the LEDs new.
Scavenging is your
first source of supply!

 

[Ira]

Logitech support said that their warrenty department would contact me
in 5-6 days. So, even if my remote is covered, which it's not, it
would take probably 4 weeks to get it repaired (1 week for contact, 1
week to ship it there, 1 week to repair, and 1 week to ship it back to
me). This is not really acceptable, so I'll continue trying to fix it
myself.

I shorted out one of the harmony diodes with a diode from an old
remote, which got the other harmony diode working. Only one diode was
blown. Also, the replacement diode did not light up; I'm assuming
this is because the current is too low to run the replacement diode.

I made some more measurements on the remote, and here are my results:

Angle between the two diodes: 25 deg
Current through one diode: 54mA
Diameter: 5mm

Note, I measured the current by connecting my DMM to the leads of the
bad diode, and pressing the volume button which seemed to give the
fastest flashes, but the current measurement may be low?

With these measurements in mind I think a diode with a 30 deg emission
angle and a rating of 100mA continuous forward current will work. I'm
going to order a couple of diode sets from Digikey, and I'll let
everyone know if I find one that works well.