Ir LED stops emitting IR 2

[felixc]

I'm repairing my old TV remote. (a vintage Sony with a metal-clad top for which I have the schematics) I expected the classic broken crystal or dirty contacts. What I found is the IR LED that still behaves like a diode, but does not emit light anymore. The IR emission can be easily seen through a digital camera. Nothing. Checked with a scope, the waveforms were okay around the LED, the ASK modulation lokked okay. Just to make sure I've put a visible LED in place, and the LED was correctly emitting visible light. The IR LED was buzzing off in one direction and giving a Vf of about 1.5 volts in the other. So electrically it looks fine. Sure the next step is to buy a replacement LED, but has anyone seen an LED stopping to emit light and still behaving like a good diode?

 

[Skogsgurra]

No, haven't "seen" that - not even with an IR detector.

The 1.5 V you mention sounds more like an ordinary red LED. IR LEDs are usually around 1.3 V. Something funny may have happened - don't throw it away!

Gunnar Englund

http://www.gke.org

 

[itsmoked]

Sure, just remember which came first! There were diodes before they coaxed them into emitting light. So something has changed so this one has failed in a manner so it doesn't produce a flood of photons anymore.

 

[zeitghost]

Leds do wear out...

 

[MikeHalloran]

Just checked my remotes with my new digital camera. Cool. The one with the dying battery was kind of dim.

Those LEDs are typically driven hard, with no current limiting resistor. Measure the current. Look for cracked solder joints.





Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Make sure you drill out the remote and put about three LEDs in, instead of one measly one. You'll reduce the missed command syndrome greatly.

Heck while you have it open put in a transistor and drive the LED really hard. If you get the drive right it will control the TV thru your hand. Just don't look into it.....

 

[fsmyth]

I know for a fact that LASER diodes can be damaged and
quit LAS-ing, but act otherwise good. Although I have not
witnessed infrareds exhibit this behavior (that I know of)
it may be a similar breakdown. Now that I think about it,
I never checked IR led's for forward/reverse; just replaced
them if there was no IR output. Interesting.
<als>

 

[IRstuff]

Laser diodes are different in that their output facets can be damaged by excessive optical power. LEDs don't tend to get that kind of output power though. Particularly TV remotes that are supposed to be eye-safe

TTFN

 

[felixc]

This Sony remote is nicely designed, as it does use a transistor and a current limiting resistor. When I get the replacement LED I'll update the thread. It was the first time I saw a correctly connected LED failing.

As itsmoked suggested, I am tempted to drill my Samsung remote though. Even with new batteries this one sucks. If I drive the LED too hard, I'll scan it over a thermal paper to decode the modulation scheme.

 

[agram]

I have seen IR LED-s behaving like normal diode but emiting nothing many times. I'm not sure in Your case, but it is a good chance that You only need to replace IR LED.

 

[felixc]

Thanks for your comment agram, so it does exist. The replacement IR LED is on my list for the next Digikey purchase round.

 

[itsmoked]

Yeah, gotta make that dang $20 or pay the penalty..

BTW Mouser doesn't hit you with that.

Also keep in mind that Mouser's site takes Digikey part numbers directly.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

- kcress@<solve this puzzle>

 

[MikeHalloran]

A star for Mouser. I've been dealing with them off and on for ten years or so, and have never been disappointed in the slightest way.





Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Thanks Mike.
Here's some more observations.
--------------------------------------
Annoying things about Mouser..
Their search results can be really uselessly overwhelming sometimes. You have to then step thru a zillion results trying to find what you're looking for.
Digikey's parametric search is much better.
--------------------------------------
Mouser lets you easily page thru the catalog.
Digikey flat doesn't allow it. This can be a major pain in the rear. You can search for something and land on a catalog page. Then you discover the description of that part is on the previous page and you have no way of getting to it without knowing a part number that lives there.
--------------------------------------
Mouser's paper work is totally sketchy and often incomplete. I'm often left wondering where some part actually showed up on paper. This can be especially confusing when getting three packages for an order of say 10 parts.
Digikey's paperwork is excellent. And with a NOTE added they will include the shipping charges on the packing slip. (normally missing)
--------------------------------------
Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

- kcress@<solve this puzzle>

 

[felixc]

Problem is that I'm in Canada and Mouser has no cdn office like Digikey does. So hello shipping and customs fees. I hope that they will realize how moch business they're losing to Digikey in Canada because of this.

 

[itsmoked]

Hi felixc.

You should write them.

I write both of them often and they actually make suggested changes and respond. Those two are locked in fierce competition and a clear, "Mouser help us in Canada so we aren't forced to go to Digikey" letter could be just what's needed to move up a plan or start a plan to fix that problem for you and your compatriots.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

- kcress@<solve this puzzle>

 

[felixc]

Mouser belongs to TTI. I spoke of this to the TTI salesperson quite a while ago and he said that they aren't interested to open a Mouser office in Canada. TTI themselves have offices in Canada but they do not want to be used to channel Mouser parts. So it looks like they have chosen to stay out of the canadian business area.

(your nickname is consistent with your company's name aren't you afraid that it may scare people? )

 

[felixc]

Well, I installed another IR LED from Sharp, and it works like new!

Two things, I used to identify the polarity of LEDs by looking at the inside of it, the larger part being the cathode. Wrong! On the Sharp LED the bigger part is the anode. Then I tought oh yeah, the flat. Yes the flat designated the cathode correctly.

The forward voltage was around 1.6 volts for the Sharp LED as well as for the other one that ceased to emit light.

 

[itsmoked]

Thanks for the feedback..

We're all glad you don't have to get up now everytime to change channels....

Naw the name doesn't seem to scare anyone too badly!
Of course a lot of stuff I design gives off smoke as it is often controls for heating processes.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com