Putting more powerful led in 6131?

[SemperFi]

I bought a 6131 but I don't like it. I have to have the remote pointed directly at the device. I have a radio shack that I just have to point in the general direction.

I was wondering if I can put in a brighter led to remedy this in the 6131? I hate the action of the radio shack buttons but I get really annoyed with the 6131. With the radio shack I can point at my tv to operate my tivo which is about 8 inches below my tv. With the 6131 I have to point it directly at the tivo before it works. I used fresh batts and tried another to be sure.

Does this have something to do with the lens cover over the led on the radio shack? The 6131 just has led sticking out of the case.

[The Robman]

One of the first things I do when I modify the URC-6131 is to push the LED out further than it normally goes. While this won't make it a super-powered remote, it will improve it's performance.

We've discussed other possibilities before. Maybe Tommy Tyler has some electrical wisdom to share.

[afaa]

I'm interested in this topic. What are the other possibilities Rob?
Please excuse my ignorance, but why wouldn't a simple swap of the LED to a better one work? Or maybe reduce the resistance to the LED to increase the current to it?
This would effectively giving more juice to the LED. I know I've done this with the regular green LED from ratshack and it works good. Pushing more current to the LED makes it brighter assuming the LED can handle it.
Dont know about the IR ones in the remote.

[The Robman]

I'm not an EE, but AFAIK reducing the resistance is the best option, followed by replacing the IR-LED. The trick is finding a more powerful IR-LED.

[afaa]

OK, So here comes the next question.
What's a more powerful IR-LED and where to get it? Has anyone else done this?

Or if we know the specs for the IR-LED to one of the proven remotes we can then use that criteria to search for new IR-LEDs from Digikey or other electronic stores.

[johnsfine]

Any chance of finding the specs on the IR-LED that's in there now?

If you just reduce the resistance, you run the risk of burning it out.

Probably SemperFi hasn't yet tried your initial suggestion of just pushing the out LED a little further. I assume the actual ligh emmision point is moderately back from the tip of the LED body, so the angle from that point to the hole in the case may be narrower than it looks. It won't help to make the LED brighter if the case is blocking the signal.

[SemperFi]

No I haven't tried pushing out the led. I will give that a go.

As far as replacing the led goes I'm no engineer mind you, the color measured in wavelength I would think is important. Also then intensity is measured in mcd. I don't know what it stands for. I bought this http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 6&tc=photo It has a lot of specs. The uv led says 100 mcd. That seems really low. I bought some white ones that are 10,000 mcd. I went to ratshack and another local company's website and looked up uv led and could find no specs to compare to.

It looks like I am getting super bright assortment except the uv ones. I am glad I only asked for 5 of those.

I looked at the one for all site for anything a little more technical but I didn't see anything.

[mr_d_p_gumby]

Also then intensity is measured in mcd. I don't know what it stands for.

millicandelas, a measure of light output.

It looks like I am getting super bright assortment except the uv ones. I am glad I only asked for 5 of those.

I'm afraid you'll have to return the uv LEDs, you need IR LEDs for the remote...

Or maybe reduce the resistance to the LED to increase the current to it?

While in concept reducing the resistance sounds simple, it's probably not advisable in this case. The IR LEDs are already pushed pretty hard to current levels beyond their steady-state ratings because the designers assumed pulsed operation with much less than 50% duty factor. The existing resistors are very low in value and reducing them much further would essentially be connecting them right across the batteries.

[johnsfine]

An IR led has a rather low voltage drop, so when you put two in series you may get only slightly less current through them than would have gone through just one. So you get nearly twice the IR output.

Is there room to cut the hole in the case slightly larger and add a second IR LED?

Don't connect them in parallel, even though that's an easier modification to make. They don't work well in parallel.

[afaa]

Very interesting discussion.

The IR LEDs are already pushed pretty hard to current levels beyond their steady-state ratings because the designers assumed pulsed operation with much less than 50% duty factor.

I'm no EE either but my understanding is that LEDs in general have a 10% variance in current capacity. So dropping say 10% resistance to the LED would yield 10% gain to the IR output.

An IR led has a rather low voltage drop, so when you put two in series you may get only slightly less current through them than would have gone through just one. So you get nearly twice the IR output.

Assuming this is true, where and what kind of IR-LED to get?

[mr_d_p_gumby]

I'm no EE either but my understanding is that LEDs in general have a 10% variance in current capacity. So dropping say 10% resistance to the LED would yield 10% gain to the IR output.

The published specs from the manufacturer can be thought of as a guaranteed minimum value. In other words, under the stated conditions of temperature, current, etc., the manufacturer guarantees that the LED will not blow up, and that the light output will be within a certain tolerance. There are variances in the semiconductor manufacturing process, and some of the LEDs will be able to withstand a higher current. If you increase it by 10%, about all that can be said is that some of the LEDs will fail, and some won't.

The point I was trying to make is that in these remotes, the resistor is probably not the only factor in determining the current supplied to the IR LED. In some cases, particularly in 3-volt remotes, the resistor is very low in value and is primarily intended to prevent excessive power dissipation in the transistor that turns the LED on. In these cases, the current supplied to the LED is mostly limited by the batteries themselves.

Another factor to consider is the shape of the light beam emitted by the LED. Sometimes in remotes that use 2 IR LEDs (like some of the Radio Shack models), one LED has a very directional beam pattern, while the other has a wider beam. The directional beam is brighter and will work over longer distances, but requires more accurate aiming. The other LED has a shorter range, but doesn't require the user to have good aim.

[Entropy]

The uv led says 100 mcd.

Actually, that seems absurdly high for a UV LED.

Two things about candela ratings - Candela ratings are a measure of peak intensity, not total output. You can easily have an LED with a high candela rating that has low light output (narrow beamwidth). If you want true comparisons of total LED light output, try to find some lumen ratings. (Good luck... Only high-end LEDs such as Luxeon Stars have published lumen ratings.)

Second thing about candela ratings (and lumen ratings) - they are a measure of brightness of visible light, compensated for variations in the eye's response. The result is that a deep blue LED with the same output power as a turquoise LED will have a much lower lumen rating because the eye is less sensitive, and if the patterns are equal it will always have a lower candela rating. And most importantly, an ideal UV LED will have a lumen/candela rating of 0 no matter what the output power. (In reality there is some visible emission.)

Same goes for IR LEDs... Lumens/candela are meaningless for IR LEDs because they only apply to visible light.

[SemperFi]

Entropy, that was some interesting info.

I am not too interested now that someone pointed out above I can't replace IR with UV.

The thinking must have been cloudy the night I started this thread. Not to mention the pushing out the LED helped quite a bit.