IR Hack - additional LEDs in parallel

I was thinking about hacking a TV remote by adding additional LEDs to it, hopefully making it stronger and more likely to reach the robot through all sorts of visual obstacles.

would wiring additional LEDs in parallel enhance the signal?
Electrical circuits are not my strong side.

I can gather that the additional LEDs will lower the overall resistance of the circuit, thus increasing the current draw which should theoretically increase the power p=VI so for a given V=const, larger I means larger P, right?

also does anyone know if all Remote controls use an interchangeable IR LED? could I dismantle some from any old remote?
could I buy a bunch at the local electronics supply store?
thanks for the help!
-Leav

There is no easy answer, but in general, you have it right.

Putting more LEDs in parallel (they are voltage devices, so they all need to see the same voltage) will add to the collective light output - to a point. The point is reached when whatever is supplying voltage to the LEDs can’t give any more - that’s the larger P you noted. Some remotes can drive more LEDs than others. (Some are brighter than others, too!)

Most IR LEDs are the same, or same enough for this purpose. Instead of hacking apart another remote (which should work OK), go to radio shack, spend the dollar and buy an IR LED brand new. Be sure to get polarity correct!

For teams who want to pump out enough IR light to melt aluminum :ahh: you can put a properly designed Op-Amp circuit between the LED output and the bunch-of-LEDs, there are Op-Amps that can drive a dozen or more LEDs easily.

Just be advised that you really will not need a lot of IR light, and excessive light will only interfere with everyone - including reflections that will hurt your own range as well. One or maybe 2 LEDs should be more than enough for the 50 or so feet you’ll need it for.

Don

Rather than use a complex op-amp circuit, generally used in analog circuits, an IR remote is a fairly simple digital circuit. A high current power mosfet or transistor should do the trick nicely. Having an IR array of 40 LED’s should do nicely strapped to the bottom of a remote…or palm m100

Before we all get out of control here…
Most remotes have a either a transistor switching current to the LED or the output of the encoder drives the LED direct. Regardless of the design, the LED has a series current limit resistor to set it at the correct forward operating current. If you were to put LEDs in parallel, the added current across this resistor will raise the voltage drop across it, in effect sharing the current between the two. You could add another series resistor for each LED but you could still damage the remote control’s output stage which may not be repairable. But there is still another problem in your way and the reason that remotes generally don’t carry more than one LED. Think back to your wave tank experiments in Physics. Two emitting devices will cause interference where sometimes the waves will entirely cancel out and others where the waves will add. The position of the interference is relative to the distance between the two emitting devices and their individual radiated signal. Your best bet is to experiment with the remote you have and see what the effective distance is. My Sony universal can change channels from upstairs if I aim it at the wall in the stairwell. That is reflecting off a wallpaper surface and hitting the TV at an angle at least 45 degrees off axis with a total path loss of at least 30 ft.

We modified our remote to have 1.5 watts of power (by hooking in a external battery pack) we also wired in five LEDs that are high intensity, Overall it increase rage by about 70%. So to anwser you question, It works!

"We modified our remote to have 1.5 watts of power (by hooking in a external battery pack) we also wired in five LEDs that are high intensity, Overall it
increase rage by about 70%. So to answer you question, It works! "

I think your increase is due to the increased current through a single LED, not by having 5 of them. To increase intensity by simply adding LEDs the emissions would have to be in near perfect phase. That is only practical if the multiple LEDs are built into the same device by the manufacturer.

To increase intensity reliably here, increase the current through the LED to whatever maximum it can handle. Or replace the LED with a LED with a higher current capacity or higher intensity given the same current.

HTH

The downside to this is your IR receiver will not receive accurate commands when the robot is very up close. I do not know how to put this in technical terms but that is what I get from the IR experts.

I believe that excessive boosting of IR capabilities is a blatant violation of GP as a large enough sensors is equivalent to a jammer when pointed anywhere near other teams robots. TV remotes are designed to be highly directional devices–hundreds of LEDs wired together are not.

In addition to GP there are several other reasons not to boost your remote–you’re alliance mates may have a great deal of trouble operating their robots if you are flooding the field with IR as they start closest to you. Also an extremely strong IR signal can bounce around the field reflecting off of the various field elements creating enough IR background noise to cause your robot (and other robots) to do preform unplanned actions.

Perhaps rather than devoting so much time and energy to improving your remote you should work on directional receivers or solutions which boost power, but maintain only a thin beam of communication.

In technical terms, you can overload (saturate) the receiver. Kind of like how your eyes are saturated when a flashlight is shined directly in to them, you can’t see much of anything else.

Binome’s comments are accurate; a digital logic circuit (not sure which TTL logic family) that has a high fan out drive capability will do the trick as well, with far greater simplicity.

Al Skierkiewicz, light does indeed interfere constructively and destructively, but in a practical sense several LEDs clustered closely will not exhibit this effect over a longer distance (several feet, think ‘far field’), actually because the light beams are not all that uniform. Modulation doesn’t change this much.

Don

We did some testing with ours and we were able to run it about 40-50ft away with the reciever covered and facing away from us. I’m not sure how much you really would need to increase signal. It seemed to work fine for us.