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Differential Beacon - New Concept

 Differential Beacon  - New Concept


The Idea is So:-

Take 2 TV Remote control units - place them close together but separated by a (large) light-proof card.

On TV Remote 1 stick down the for example the "Right" button so it continuously streams out "Right" code commands.

On TV Remote 2 stick down the for example the "Left" button so it continuously streams out "Left" code commands.


So now you have two separate areas - one being blasted with "Right" code IR signals the other being blasted with "Left" code IR signals - light travels in a straight line so the light-proof card in the middle should keep the two areas relatively free from cross talk.

By using an IR RX module   IRRX_0.jpg

on your Bot, it will pick up the signals ie either "Right" code or "Left" code depending if it is left or right of the centerline.


The differing codes can be used to guide the Bot directly to the beacon.

This is just a concept - not tried yet - but on the ToDo list.

How does this idea Grab you - any refinements or comments would be welcome.


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Allright guys, yes you are all right about the IR bouncing all over the room. Yes. And I have tried this very set-up including putting the emiters in tubes with no-go results. The solution is putting the sensor in a very small tube. With my sensor in a 2" long tube with a 1/16" hole in the end, I had 100% repeatable results finding the center of a beam coming from an unshielded IR led. These "repeatable results" means I could "find" a beam within +or- 2 servo steps.

Now the in this video, the code was written very poorly, quickly and does not reflect the quality of the sensor set-up. However, the proof of concept is wicked solid and with a little refinement of the code, I think the robot could center itself in just a couple moves.


Similar setup with a 6mm diameter tube with a length of about 80mm(3 inches). In most cases I can read the data clearly.

This was tested with 2 beacons and a 40 degree sweep for the tests. 



I like the general idea, the code would be very similar to a line follower. I agree with Jklug80 that reflection off walls and furniture would be a problem. Reducing power to the IR LED until it can barely be detected from the far side of the room would be your best bet.


Doesn't the IR's bounce quite a lot?

I don't have to point the TV remote at the TV at all to change channel. That would suggest that you'd need some sort of filtering to make sure that it's only the direct signal that gets picked up by your bot. 

I've mentioned that numerous times and no one has ever said anything about it. when I was playing with picaxe and IR sensors I could put the remote under the table and the robot on top of the table would pick it up. IR bounces around a LOT.
I don't recall seeing your posting on this issue, as if I had I would have posted/responded on it. I've done quite a bit of experimention with ir as I've been working on my beacon project.
Maybe its better to put the IR leds into tubes and narrow the beam a bit - just a thought

It's easier to put the sensor in the tubes than the emmiter. though you could but the emmiter in a box that has a narrow field of view out to reduce the ir exposure.

 Edit, putting the sensor in a tube that is wrapped in black ecletrical tape seemed to do the trick for me.

Shrink wrap around the emmmiter also would work for keeping the emmiter directional, but that wouldn't be ideal for the beacon I would imagine as  you 'd want the sensor to be able to detect it from various angles/locations.



 You might get some design ideas from the Pololu IR Beacon.



Sounds good but it will require some tinkering. As it gets close or even far away from the card it will still pick up both signals unless the robot is on either side of the card.