IR Jamming from 2 or more remotes - results

We ran a few tests yesterday which confirm a lot of what others have said regarding IR jamming. We also went through the effort of switching IR receivers with those sensitive to different carrier frequencies.

The receiver on the IR board is sensitive to 38kHz.

We ran an additional board with a receiver sensitive to 36kHz, and another at 56kHz.

What we found was that an IR remote transmission at any of the 3 frequencies was able to jam another at any of the 3 frequencies.

Is anyone else worried that a RoboCoach, by simply holding down a button on a remote, might effectively render a good part of the field "IR-useless?"


I suspect that part of the reason the robocoach stations are positioned where they are is to help prevent inter-alliance jamming.

I’m trying to lead our hybrid design in a direction that minimizes our emissions both to avoid adding to the problem and to reduce our vulnerabililty to it.

Thanks for the reply. Would you be willing to share ideas on this, in the thread? The reason is, we’re now initiating the same type of design, BUT it is dependent on what all the other alliance IR emissions are.

I think it will be vital to get the word out to all teams expecting to use IR, that they WILL need to do more than just use a TV remote.

FYI, I believe your alliance may CHOOSE which end of the field your RoboCoach will be stationed at, meaning you could have opponent RoboCoaches beaming IR commands right beside you.

My gut feeling is telling me to do this:

  1. Add a lens in front of the IR LED. Make sure it produces a nice parallel beam, that spreads only enough to give some margin of aiming error.

  2. Throw bright visible, non-interfering LEDs around the IR LED, so you can see your beam, and know where you’re aiming.

  3. Make 6 of these, and ask your alliance partners and opponents use them if they haven’t already got something cooked up.

The way I can see it, there are two concerns here

  1. There may be times when you will not be able to communicate with your robot because of other team’s IR.
  2. Your communications with your robot might interfere with your alliance’s communications

A solution to #1 is to make sure that you don’t have any time-dependent routines among your 4 hybrid modes. For example, rather than having “drive forward” as a response to a given button press, have “drive forward 5m”. Rather than “turn left”, have “turn left 90 degrees”. This way, a sudden loss of your ability to communicate will not doom your robot in hybrid mode, it’ll just mean you will start your next command a little later once the interference clears.

A solution to #2 is probably more difficult. Perhaps you could make an IR ‘gun’, with a long IR-absorbent tube in front of your remote’s IR emitter, to increase your aiming accuracy. On the robot, mount a little visible-light LED that lights up to confirm reception of the command so you know when you ‘hit’. Another solution would be to simply co-operate with your alliance partners so that only one of your is signalling at a given time.

FYI, I believe your alliance may CHOOSE which end of the field your RoboCoach will be stationed at, meaning you could have opponent RoboCoaches beaming IR commands right beside you.

The opponents may be beside you, but the lane divider will be between them and your robots at the start. Someone should check if the material the lane divider is made of is opaque to IR transmissions. If it is, then the only interference your robots will deal with at the beginning of hybrid mode will be from your alliance partners.

Or: “Drive to ball position #2, knock down the ball, then proceed to drive laps while avoiding other robots”

Our programmers are thinking big…we’ll see how it works out… :slight_smile:

My emission control strategy is more tactical than technical. If we get the autonomous part of our hybrid mode to work properly, the robocoach will signal two or fewer times, which should leave a lot of available airtime for our partners. Add to that a bit of shielding on the robot to make sure that we don’t pick up signals from the remote robocoach station or the opponent stations, and we should be fairly interference-friendly.

Adding a targeting/transmit warning LED to the remote to help the alliance coordinate against interference would probably be a good idea. If you’re looking to loan them out, how are you looking at making them modular enough to work with a variety of remote shapes?

Gents, sorry to reign this thread in, but the issue isn’t what your robot should do once it receives an IR signal.

It’s receiving an IR command at all!

Waiting for the interference to clear up, and sending a non-time dependent command isn’t a viable solution. Neither is sending a “do everything” IR command. Both won’t cut it if they never get to the robot.

RoboCoach 1: hits IR command and holds it

RoboCoach 2: hits IR command, it doesn’t work. Thinking he can sneak in the command when “interference clears up,” he continues to hold the IR command, hoping everyone else will let up, even for a split second.

RoboCoach 1: IR command is now jammed by RoboCoach 2. Thinking he can sneak in the command when “interference clears up,” he continues to hold the IR command.

Deadlocked :frowning: ?

Actually, it is about what your robot does with the command, because if you are really clever with your programming, your robot will only need one command at the beginning of hybrid period that will tell it what to do for the rest of the period, and you can just ignore the IR inputs after it receives that one command. Jamming problem solved.

Just make sure you’re never stuck as “RoboCoach 2” above :smiley: .

yeah…you would want a directional tube on the IR reciever, and some cooperation with your alliance partners!

We bought a couple of “Fyre Fly” IR Transceivers ( and have been experimenting with them. Although operating at IRDA wavelengths, they have a different carrier frequency. The range is about 100 feet with both the narrow and wide LEDs running at 12VDC, line-of-sight, in a dark room. TV remotes don’t seem to interfere with their IR. We are head-mounting one of them on our robotcoach, and are trying to figure out the best mounting configuration on the robot.

What about an entire remote? If a team (alliance member or opponent) gave you a custom remote that had a targeting light (illuminates where it’s pointed), indicator light (shows when in use), and a nice tight parallel IR beam, would you be willing to re-train your IR board to use it?

Or would you insist on using your own IR remote?

Or what if you supplied your entire alliance with three remotes wired together via circuit that prevents them from transmitting at the same time? Or even does some clever time-slicing?

I agree, any attachment requiring integration of existing remotes would be messy.

I still don’t see the big problem if you set up the robot to accept one of 4 commands at the beginning of the period, and then ignore inputs after that.

all that is required is that you coordinate with your alliance partners as to when you will be sending a signal, and make sure you don’t both/all3 try to send a signal at once, and that you have your IR board set up to be somewhat directional (pointing towards your corner of the field).

The problem is that a malicious opponent (or overzealous alliance partner) could simply hold a button down and flood the playing field with IR, thus preventing you from sending your command if he starts before you do.

Gents, sorry to reign this thread in, but the issue isn’t what your robot should do once it receives an IR signal. …

There are two cases here:

  1. The interfering IR source is your allies. In that case, ask them to stop driving-by-remote for a second and send your command. Maybe afterwards, help them code up a routine that requires less IR input.
  2. The interfering IR source is your opponents. It might be a good idea to put a IR-opaque shield on the left side of your board, since your opponents will always be on the left side of your robot to start. This will prevent them from being able to interfere with your own IR communications. So at least, you’ll be able to get a single command in before your robot makes the first corner and enters your opponent’s zone.

Another idea I just had:
-Mount the IR board on the rear of the robot facing backwards so that it is facing directly towards your alliance robo-coach station. This will reduce the set of potential interfere-ers to only your alliance partners, over whom you have greater control.

Well now that people have realized that this is a problem there are several ways to go about solving it–the most obvious is to avoid using the supplied IR equipment altogether and go with a different signaling mechanism.

You could also have your robot wait 3 secs for a command and then begin a default autonomous period.

Oh and Squirrel–The problem is that you may not even be able to get that first command to your robot because everyone is trying to do the same. As your alliance partners are all pointing their remotes right where you are pointing your you may end up not able to do anything.

In our tests, we could get a command in every few seconds with 1 remote jamming, but not with two.

You wouldn’t be aiming your remote at your alliance partners’ robots. Why would they be pointing theirs at yours? And if you narrow your sensor’s field of view enough, only one remote will be visible to it anyway.

I think I’ll suggest mounting our IR sensor near the floor, with a shield above it. Only someone holding a remote a few inches off the ground should be able to get a command through to it.

Your alliance partners start the match very close to your robot–It would require a very directional sensor on everyone’s part not to be pinging other peoples robots.

Something as simple as a paper towel tube ought to suffice. Consider bringing a handful of them to the field and handing them out to your alliance partners if it looks like they’ll be spraying IR all over the place.

Shhhhh … dont tell them our secret :stuck_out_tongue:

I toilet paper roll tube for the robot … 50 cents and Cots (once roll is used :stuck_out_tongue: )
1 paper towel roll tube for robocoach … 50 cents and cots (again once roll is used :stuck_out_tongue: )
Being able to block all IR but your own for the initial command … priceless