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IR Emitter Question
This thread has 14 replies. Displaying all posts.
Post 1 made on Tuesday October 10, 2017 at 03:49
montyy
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Hi All,

Sorry if this isnt in the right section I am new here.

I recently started a installation with a RTI XP3 where due to cabling requirements I am needing to join IR emitters but am having issues.

From my IR port from the XP3 I have the jack cable which splits into a cable that has two IR cables connected to it in parallel. E.G A 4c cable from the tvs needing to be IR controlled using red and black on IR1 and IR2 using white and green which then connect onto the stripe/non stripe of the IR output jack cable respectively. I have checked the cable connections which are correct and I have also tested those cables for any faults which they are also fine.

IR1 works fine but not IR2. If I disconnect IR1 then IR2 functions correctly.

Is there anyone who can shed some light on this for me? I know you can get double IR emitters but due to the distance between the TV's this will not work for me. Is it even possible for me to parallel up the 2 IR's in this configuration?

Thanks!
Post 2 made on Tuesday October 10, 2017 at 08:19
buzz
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Parallel is not a viable plan unless the the two emitters (diodes) have absolutely identical characteristics (there is virtually no chance of this fortunate accident occurring in the field). Since they are not identical, one emitter till turn on first and cap the voltage below the other emitter's turn-on voltage -- exactly duplicating your results.

The solution is to wire the emitters in series. Don't carry this to far, two or three will usually work, sometimes four. The output of each emitter is lower, but this is typically not an issue.
Post 3 made on Tuesday October 10, 2017 at 10:26
Mario
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Or get an IR connecting block.
[Link: google.com]
Post 4 made on Tuesday October 10, 2017 at 14:08
Ernie Gilman
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On October 10, 2017 at 08:19, buzz said...
Parallel is not a viable plan unless the the two emitters (diodes) have absolutely identical characteristics (there is virtually no chance of this fortunate accident occurring in the field).

EXACTLY, except since LEDs are made in batches, with all in the batch having values very close to one another and packaging happening in batches, it's quite possible for them to turn on at the same voltage. The problem is that you can't plan on it, so a method should be used that solves the problem before you even see it.

Since they are not identical, one emitter will turn on first and cap the voltage below the other emitter's turn-on voltage -- exactly duplicating your results.

Yes, EXACTLY.

The solution is to wire the emitters in series. Don't carry this too far, two or three will usually work, sometimes four. The output of each emitter is lower, but this is typically not an issue.

This will probably work if the IR system uses a 12V supply, but I've seen them using 5V supplies. Two LEDs in series off of five volts gives you limited output current. Three probably simply won't work.

So it's good that there's another solution, which is exactly how IR distribution blocks are made: wire them in parallel, but add a resistor of, say, 100 ohms in series with each LED. (In some power amplifier circuitry where transistors are more or less in parallel, such resistors are called sharing resistors.)

Think of what happens when you have two LEDs in parallel that don't start to conduct at PRECISELY the same voltage, and you apply an IR emitter voltage that increases from zero.

A crucial point is that an "IR emitter voltage" is a signal with resistance in series with it.

At some voltage, one of the LEDs turns on. A further increase in the applied voltage will only make the LED conduct more current. The voltage across the LED won't change* and the other LED won't turn on because that voltage isn't high enough to make that one start to conduct.

If you have a resistor in series with each LED, once the first one turns on, the voltage at that LED won't get any higher, but the voltage applied to its series resistor will get higher... this voltage is also applied to the second LED through its series resistor, and when that voltage gets high enough, the second LED will also turn on. The fact that the two LEDs don't turn on and off at exactly the same voltage won't matter because the added resistors have forced the voltage and current to be shared between the two LEDs. This is why those resistors are called sharing resistors.






*In the real world, this is not exactly true, but it's okay to assume it's true as the real voltage change is minimal.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 5 made on Wednesday October 11, 2017 at 00:34
tomciara
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I see your technical reasoning behind why two emtters in parallel will not work. I also see the original poster can't get them to work. Only trouble is, I have done it many many times without an issue.

In fact, I order what amounts to being a mini plug splitter, that would normally be used for two sets of headphones off of an audio device, and I use it to drive two emitters off of one port.

I did it today when the client wanted me to add an emitter to control his old Denon compact disc changer with his URC remote. It worked.

Perhaps there is something forgiving about URC base stations, or URC emitters. Whatever the case, I have done it multiple times over the years and have never had it fail.
There is no truth anymore. Only assertions. The internet world has no interest in truth, only vindication for preconceived assumptions.
Post 6 made on Wednesday October 11, 2017 at 01:11
crosen
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On October 11, 2017 at 00:34, tomciara said...
I see your technical reasoning behind why two emtters in parallel will not work. I also see the original poster can't get them to work. Only trouble is, I have done it many many times without an issue.

I've been able to do this with Control4 emitters consistently.
If it's not simple, it's not sufficiently advanced.
Post 7 made on Wednesday October 11, 2017 at 02:26
Ernie Gilman
Yes, That Ernie!
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On October 11, 2017 at 00:34, tomciara said...
I see your technical reasoning behind why two emitters in parallel will not work. I also see the original poster can't get them to work. Only trouble is, I have done it many many times without an issue.

That's not trouble. As I mentioned, LEDs are made in batches and the units in the batches are substantially identical to one another. That means that in the usual world of manufactured double LEDs, or taking two LEDs from a package, they will most likely work. I said we should use sharing resistors to ENSURE that any possible different turn-on voltages won't cause failures. One unmatched pair will drive you nuts until you remember this thread, so I recommend standardizing on curing the potential problem first.
In fact, I order what amounts to being a mini plug splitter, that would normally be used for two sets of headphones off of an audio device, and I use it to drive two emitters off of one port.

Are these emitters probably from the same batch? Do they have resistors built into them? (To test this, vary the voltage applied to them through a resistor. If, after the LED starts to conduct, the voltage across the LED [or LED plus resistor] increases as the applied voltage increases, then there's a resistor built in in series with the diode.)

See, it doesn't matter if these have all worked. What will matter much more to someone is if a pair doesn't work.

I did it today when the client wanted me to add an emitter to control his old Denon compact disc changer with his URC remote. It worked.

Perhaps there is something forgiving about URC base stations, or URC emitters. Whatever the case, I have done it multiple times over the years and have never had it fail.

If the URC emitters have resistors in series with the LED, that would take care of the potential problem.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 8 made on Wednesday October 11, 2017 at 06:42
montyy
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Absolute legends, cheers guys for the help and espically the in depth explanation of how the issue was caused.

All is working well now!
Post 9 made on Wednesday October 11, 2017 at 08:21
buzz
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On October 11, 2017 at 00:34, tomciara said...
Perhaps there is something forgiving about URC base stations,

I have never looked into the exact details of the URC emitters and base stations, but if they include a series resistor in each emitter, this may create enough isolation between LED's to enable parallel connections. If there is a series resistor in each controller output, then the value and ratio between this resistor and any resistors included in the emitter become important.

Series resistors in the controller outputs attempt to protect from excessive external loads. Series resistors in the emitters protect the LED's from potential excessive current that may be available from the controller (depending on its output impedance).

Some of these little combiner/splitter boxes are a simple resistor/diode matrix, while others have separate drivers for each output.
Post 10 made on Wednesday October 11, 2017 at 16:17
Ernie Gilman
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Everything in this post is true. Everything in this post becomes moot if a person will just submit to the fact that Xantech does it right every time.

On October 11, 2017 at 08:21, buzz said...
I have never looked into the exact details of the URC emitters and base stations, but if they include a series resistor in each emitter, this may create enough isolation between LED's to enable parallel connections. If there is a series resistor in each controller output, then the value and ratio between this resistor and any resistors included in the emitter become important.

Use Xantech distribution blocks to expand the number of LEDs you run off of one output, but be aware that LED outputs already have a resistor in them, so you might not be able to run more than two LEDs. The screw terminals and jacks of these terminal blocks keeps you from having taped or crimped connections in the air where they can get snagged and broken.

Series resistors in the controller outputs attempt to protect from excessive external loads. Series resistors in the emitters protect the LED's from potential excessive current that may be available from the controller (depending on its output impedance).

And all of this is moot if you'll just submit to reality and use Xantech products.
Some of these little combiner/splitter boxes are a simple resistor/diode matrix, while others have separate drivers for each output.

The 789-44 is just connectors and resistors. Other products have resistors, some have amplifiers so even more LEDs can be driven. But did I say... Xantech?

Oh, yes, another thing that's often misunderstood about the 789-44: it's two separate products wired together properly.

It has an input for 12 volts, and a jack for an IR sensor. That jack supplies 12 volts to run the sensor. The output of the sensor is available at the output screw terminal. This output is connected to the otherwise independent second part -- distribution. Distribution consists of that sensor output terminal plus four ports. Each port is a resistor feeding an LED output jack.

The often-missed point is that there is ZERO need for a 12 volt connection to the 789-44 if you're just using it to go from an IR signal to four IR LEDs. That 12 volts is ONLY for powering an IR sensor. If you don't use one, you don't need a power supply connection.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 11 made on Wednesday October 11, 2017 at 17:24
Mac Burks (39)
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Ditch the blinking emitters and go with non blinking.
Avid Stamp Collector - I really love 39 Cent Stamps
Post 12 made on Wednesday October 11, 2017 at 17:29
Ernie Gilman
Yes, That Ernie!
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I like the blinking emitters because you can SEE if they're working. It's not nearly as easy to see non-blinking LEDs using a phone, but it's possible. I've also heard there's a bit more of a voltage drop across blinkers, meaning they won't perform as well in series. I haven't needed to pursue that.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 13 made on Thursday October 12, 2017 at 00:09
Mac Burks (39)
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On October 11, 2017 at 17:29, Ernie Gilman said...
I like the blinking emitters because you can SEE if they're working. It's not nearly as easy to see non-blinking LEDs using a phone, but it's possible. I've also heard there's a bit more of a voltage drop across blinkers, meaning they won't perform as well in series. I haven't needed to pursue that.

I like them for the same reason...but...in my career i have only experienced 2 IR related issues. I have used speaker cable, RG6, Cat5. mono (and stereo when forced) 1/8" extenders to extend IR emitters.

The two issues have been

#1. More than 1 blinking emitter on a single IR output caused them both not to work. The solution was to replace with non blinking emitters.

#2. With a Phast Card Frame and IR Receiver card i found that i could not use Cat5 to extend IR receivers. We Kustomed IR receivers into the in wall speakers so that they would hide behind the grill. We used Pronto TS-1000's in each room to send commands back to the rack. The IR receiver card had 3 ports. Signal would jump across the Cat5 to all ports causing the TV channel to change in all 3 rooms. The solution there was to buy 2 additional IR receiver cards and put each IR receiver on its own card.
Avid Stamp Collector - I really love 39 Cent Stamps
Post 14 made on Thursday October 12, 2017 at 01:46
Glackowitz
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On October 11, 2017 at 17:24, Mac Burks (39) said...
Ditch the blinking emitters and go with non blinking.

It looks funny when you light up a cabinet with 4-5 blinking red lights when you volume up or change channels. It’s as bad as a blinking 12:00 on the vcr.
There's no worse feeling than that millisecond you're sure you are going to die after leaning your chair back a little too far.
Post 15 made on Thursday October 12, 2017 at 02:30
Ernie Gilman
Yes, That Ernie!
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On October 12, 2017 at 01:46, Glackowitz said...
It looks funny when you light up a cabinet with 4-5 blinking red lights when you volume up or change channels. It’s as bad as a blinking 12:00 on the vcr.

But isn't the entire purpose of having IR emitters on the components that they are in a cabinet and you want to be able to close the door? Close the door!

On October 12, 2017 at 00:09, Mac Burks (39) said...
I like them for the same reason...but...in my career i have only experienced 2 IR related issues.

I had the coolest one in a home in Malibu that faced due south.

During setup we found that the IR didn't work. It was a Xantech system. We kept assembling components. The next day, all was good. Then it didn't work.

We finally figured out that the IR system didn't work for about 90 minutes in the afternoon... when the sun's light was bouncing off of thousands of individual little waves in the ocean and into the room.

The cure was to close the curtain in front of the south-facing windows. This required planning because the curtain had a Makita drape control which was run by... IR.

When the sun wasn't quite due south in the sky, the system resumed operation.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw


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