Strength of jack signal

[Mastiff]

Hi!
I have connected an external IR diode to the jack, one that I have from a set of IR extenders. But the signal is much weaker than when used with the IR extender. With that I can control everything from the other side of the room, with the jack out on the USB-UIRT everything beyond 3 feet is impossible. Is it possible to adjust the power of this in any way, or is that set in stone? And is it possible to find emitters that can blast any better? I would like two, or even four connected to it, so I can put emitters in the rooms instead of the IR extender senders. When there's an IR emitter receiver in the same room as the sender, the loop creates problems when controlling some equipment.

Thanks in advance!

[jrhees]

First of all, I would assume that you are using a SINGLE IR LED, and not multiple in series.

There are two things you can do here (besides an amplified circuit):

1) Go for a more efficient IR emitter. Emitters come in all specifications, and some must be driven very hard, and others are designed for efficiency (much the same as speakers). You really have no idea what 'flavor' comes out of a piece of existing equipment.

2) Reduce the series resistance built into the USB-UIRT's emitter circuit. To do this, you'll have to be somewhat skilled with a soldering iron. This involves opening up the USB-UIRT and replacing (or easier, adding across the existing resistor) a resistor in the circuit with a lower-value one.

There is some limitation on how far you can go with increasing the current. Because the USB-UIRT is powered off of the USB bus, there's a limit to how much current we can pull. Often amplified emitters will drive literally >1 amp into IR LED's for short bursts. The USB-UIRT uses high-efficiency emitters to try and eek out a bit more with the limited current budget.

-Jon

[Mastiff]

Thanks for the quick answer!

Yes, I tried with single LEDs, but I would like to use multiple in parallel, if possible. But finding a better emitter might be a problem, I guess, since I can't see what kind is efficient. Do you have any types you can recommend?

As for reducing the resistance won't that hurt the internal IR emitter? I assume the ristance is built on what that emitter needs/demands. Or is there a good marginal there? My brother is an electronics engineer, so he's really handy with his iron, so to speak... What ohm value is there now, and what value should be put in as a replacement?

Thanks again!

[jrhees]

There are (3) Three internal resistors in the USB-UIRT.

- One is for the internal LED's, and is very low resistance. This shouldn't need to be changed.

- Two others feed both the tip and ring connections on the 1/8" jack. The jack is STEREO and this was done so that those handy with electronics could have two separate current-limited outputs on the 1/8" jack.

You can change one or both of these two resistors. They are surface-mount 1206-size components. Each is 82 ohms.

Probably the easiest thing to do is simply to tack another resistor on top of these resistors in parallel. This is far easier for most than lifting the old part.

You can probably go down to as low as 10 ohms. Be careful, though about the following:
Since the 1/8" jack is stereo and I have wired a separate limiting resistor to each (left and right) channel connection, when a MONO plug is inserted into the jack it essentially shorts one channel to ground. This is not a problem when 82 ohms is installed, but if you lower this resistance you'll end up loading down the drive transistor too much. Unless you're planning on wiring a stereo connector, I would suggest changing ONLY the resistor which feeds TIP.

-Jon

[Mastiff]

Thanks again! I have spoken to my electronics/computer engineer brother and he'll do it for me this weekend! So you'll hear how it went on Sunday or Monday. And I actually will be using stereo plugs, so he'll change both. I'll only mark the jack on the UIRT with "Stereo plug only" and attach a splitter plug right away.

[Mastiff]

Well, the deed is done. I tested with different cable resistors, from 50 (which almost put me back to the 80 you originally had) and down. I had to go all the way down and use nothing but cable, but now it works great!

I have one emitter on the side of the bedroom that's opposite of the TV and receiver (only around 8 feet, though), and that controls them both. As for the living room set it turned out that it was a bit more demanding, obviosly those IR-extenders put out pretty strong signals. But by using a jack to two jacks splitter and two emitters, one in the stereo rack and one just below the tv, it all works (exept for that pesky Force DSS receiver, of course...) . Next step will be to fit one in the home theater, and I expect no problems since this "turbo" unit obviously can run two parallel emitters without any problems. Thanks for your help!

[Quixote]

Hi guys. I'm about to undertake the same project, and I'd like a little help if that's ok. I have my UIRT set up with 3 emitters that work excellently, but I've tried to add another 2 and the original 3 no longer work. I can get the 2 to work alone, however. I'm almost certain that it has to do with the resistors you've been discussing. I really don't want to destroy my UIRT though by melting it. I'll link to a diagram tomorrow showing how I've wired the extra 2 LEDs. Any pointers in the mentime would be greatly appreciated.

Thanks!

[Mastiff]

Sorry, mate, but I can't help you. My brother did it, and I have no idea where he soldered what. But I can say that I have had this mod on my USB-UIRT for three years now without any problems. And I have added a few more emitters as well. So I'm satisfied.

[Quixote]

No problem, I'm sure that Mr Rhees can hook me up with a diagram or description. (?)
How many emitters do you have working in total?
I'll have to make that diagram today after lunch...

[Quixote]

Here is a diagram.
I've tried using them on there own, connected to the jack and they work fine, but as soon as I try to wire them in series with the original 3, either the original 3 stop working, the 2 new ones, or all of them.