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I goofed! Dead IR LED reciever /transmitter

 
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pcrider



Joined: 11 Nov 2010
Posts: 8

PostPosted: Thu Nov 11, 2010 3:41 pm    Post subject: I goofed! Dead IR LED reciever /transmitter Reply with quote

I have been messing with an older URC8810 remote trying to install codes for all my stuff which meant re-learning JP1.
Well at one point it was not doing anything to turn on the tv, and I knew the IR light should be picked up by my IR security cameras.

When it wasn't there I wondered is it the software in the remote or the LED that is dead?
So I hooked up the led to a power supply and slowly turned up the voltage while watching a camera for light.... oops, should'a been watching the voltage!

So heres the funny part, since then I have the remote working but I don't have an LED to put in it.

Now comes the question, is it an LED, or is it a IR detector diode/transistor, or is it both in one package?
I need to get one, but I have never run across this question before.
It is a learning remote, and it only has the one device(LED), so logic says its both right?
So what do they call this little wonder? Can I get one at Radio Shack?
It looks like an ordinary LED.

Thanks, PcRider
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Tommy Tyler
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Joined: 21 Sep 2003
Posts: 410
Location: Denver mountains

PostPosted: Thu Nov 11, 2010 7:05 pm    Post subject: Reply with quote

The device is an infrared LED. Although it is primarily an emitter, it will also function as a receiver and give a small electrical signal when properly biased and illuminated by another infrared LED. So it is, as you say, both a transmitter and a detector in one package.

The Radio Shack part (catalog #276-143) is a good choice for replacement.
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pcrider



Joined: 11 Nov 2010
Posts: 8

PostPosted: Thu Nov 11, 2010 7:30 pm    Post subject: Reply with quote

Tommy Tyler wrote:
The device is an infrared LED. Although it is primarily an emitter, it will also function as a receiver and give a small electrical signal when properly biased and illuminated by another infrared LED. So it is, as you say, both a transmitter and a detector in one package.

The Radio Shack part (catalog #276-143) is a good choice for replacement.


I'll pick one up in the morning and give it a try.

Thanks! PcRider
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cauer29



Joined: 03 Feb 2010
Posts: 235

PostPosted: Thu Nov 11, 2010 10:40 pm    Post subject: Reply with quote

pcrider wrote:
Tommy Tyler wrote:
The device is an infrared LED. Although it is primarily an emitter, it will also function as a receiver and give a small electrical signal when properly biased and illuminated by another infrared LED. So it is, as you say, both a transmitter and a detector in one package.

The Radio Shack part (catalog #276-143) is a good choice for replacement.


I'll pick one up in the morning and give it a try.

Thanks! PcRider


If you understand how semiconductors work, it'd be clear that applying a fixed voltage directly to an LED, is going to result in disaster. A quick examination of the VI curve for an LED, would show that the current rises extremely quickly as the voltage is increased. That's why for applications where the LED is kept on continuously, a series resistor is used to bring the near vertical slope of the VI curve down to a more manageable slope allowing for a reasonable variation in voltage without the current varying wildly. So next time you want to see if an LED is working, use a series resistor.

A.A.
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vickyg2003
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Joined: 20 Mar 2004
Posts: 7057
Location: Florida

PostPosted: Thu Nov 11, 2010 10:46 pm    Post subject: Reply with quote

I don't understand how semiconductors work, but I do know that when I was playing around with learning how to write protocol executors, I did something that caused the ir emitter to go on continuously, instead of flash, and within a minute I had killed the IR emitter. Those emitters don't like to be on continuously!
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Tip: When creating an upgrade, always include ALL functions from the oem remote, even if you never plan on assigning them to a button. Complete function lists makes an upgrade more helpful to others.
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pcrider



Joined: 11 Nov 2010
Posts: 8

PostPosted: Fri Nov 12, 2010 12:24 am    Post subject: Reply with quote

cauer29 wrote:
If you understand how semiconductors work, it'd be clear that applying a fixed voltage directly to an LED, is going to result in disaster. A quick examination of the VI curve for an LED, would show that the current rises extremely quickly as the voltage is increased. That's why for applications where the LED is kept on continuously, a series resistor is used to bring the near vertical slope of the VI curve down to a more manageable slope allowing for a reasonable variation in voltage without the current varying wildly. So next time you want to see if an LED is working, use a series resistor.

A.A.

That makes sense to me. I do know a 220ohm, or 330ohm resistor is common for current limiting on LED's. I really didn't understand it in those terms though. I just figured I would see the LED light long before it reached the critical point. I still wonder why it didn't.
In the future I will do as you suggest though thats for sure.

Thanks for the Info,
PcRider
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cauer29



Joined: 03 Feb 2010
Posts: 235

PostPosted: Fri Nov 12, 2010 10:33 am    Post subject: Reply with quote

vickyg2003 wrote:
I don't understand how semiconductors work, but I do know that when I was playing around with learning how to write protocol executors, I did something that caused the ir emitter to go on continuously, instead of flash, and within a minute I had killed the IR emitter. Those emitters don't like to be on continuously!


IR remotes obviously don't normally turn their IR LEDs on continuously, though like you, I've messed up a remote or two resulting in a burned out IR LED. IR remotes don't usually have a resistor in series with the LED or if they do, it's quite small and not sufficient to prevent burning out the LED if misprogramming results in continuous on time. IR remotes only transmit very short bursts at extremely high current compared to what the LED can stand continuously. It's not uncommon for the LED current to be in the range of 1 amp or more, where the same LED can only handle 10-20 milliamps continuously. That 1 amp of current in short bursts gives us a decent range of operation. Those little stick-on IR emitters used in IR distribution systems typically run their LEDs at very low currents by comparison and they end up with a usable range of only an inch or two.

A.A.
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vickyg2003
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Joined: 20 Mar 2004
Posts: 7057
Location: Florida

PostPosted: Fri Nov 12, 2010 2:46 pm    Post subject: Reply with quote

Thanks for the explanation.
_________________
Remember to provide feedback to let us know how the problem was solved and share your upgrades.

Tip: When creating an upgrade, always include ALL functions from the oem remote, even if you never plan on assigning them to a button. Complete function lists makes an upgrade more helpful to others.
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pcrider



Joined: 11 Nov 2010
Posts: 8

PostPosted: Fri Nov 12, 2010 11:56 pm    Post subject: Reply with quote

pcrider wrote:
Tommy Tyler wrote:
The device is an infrared LED. Although it is primarily an emitter, it will also function as a receiver and give a small electrical signal when properly biased and illuminated by another infrared LED. So it is, as you say, both a transmitter and a detector in one package.

The Radio Shack part (catalog #276-143) is a good choice for replacement.


I'll pick one up in the morning and give it a try.

Thanks! PcRider


Got it working tonight, I've tried out the learning already and that works too. I never did get to town though, I just borrowed an IR LED from another old remote that I can't use anymore. I also found jumper 6 on the board was not soldered in on one end. That may explain a lot of the trouble I was having, I'm not real sure what that jumper does.

Now to finish getting all my devices set up!

Thanks all,
PcRider
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