Looking for EV3 Infra Red Sensor and Beacon Specs

[tabbycatrobots]

Has LEGO or anyone else published specs on the IR beacon and the IR sensor? I'd like either a basic spec, or
a descriptive one that for the beacon, tells how the signal that is broadcast differs for each of
the 4 channels, and for the sensor, how well does it ignore channels other than the one specified in a program.
I think either spec would help me understand why my robot is failing.
I'm trying to build and program a robot that will in turn, seek and travel to four beacons; each beacon on its own
channel, 4, 3, 2, 1. The desired operation is for the robot to travel to beacon broadcasting channel 4, stop about
6 inches away, rotate until it detects channel 3, travel to beacon 3, stop, rotate, detect channel 2, travel to
beacon 2, etc.
Currently, if I only have beacon 4 on and start the robot, the robot travels to beacon 4 stops about 6 inches away, and
starts rotating. If I then turn off beacon 4 and turn on beacon 3, the robot detects beacon 3 and travels to it,
stops, and starts rotating.
If I turn on both beacon 4 and beacon 3 and then start the robot, the robot travels to beacon 4, but does not stop,
and it runs into beacon 4. It's as if having more than one beacon transmitting causes problems for the proximity
detection of the IR sensor.
Thanks for any ideas or suggestions.
Howard

[mightor]

There has been nothing published by LEGO regarding how the beacon works.

= Xander

[donttell]

My IR sensor is not usable in signal mode. But it is working well in the other modes. I have sent e-mail to customer service.

[holler]

The signal key on the EV3 IR remote sends a PF combo PWM command (Float) whereas the other keys do send PF combo direct commands. That's at least what I've used with the IRLink to send EV3 IR signals. The description of the "LEGO Power Functions RC" protocol describes the encoding of those signals.

Alexander Holler

[donttell]

Somewhere deep in the Ev3 manual I found information that signal mode works only in a distance range of about 70 cm to 2 m.
In my first tests I was simply too close.

Howard, did you know this already?

[gloomyandy]

Which documentation was this information in? What exactly do you mean by "signal mode". The Lego docs talk about proximity, beacon and remote control mode...

[donttell]

In the German documentation Lego calls the beacon mode "Signal Mode".
I found this distance information on the Lego Education site describing the IR sensor in more detail:
http://www.legoeducation.us/eng/product ... ensor/2571

And there is again a difference between the wording in the German version compared to the English version.
In my oppinion the English version is totally unclear. Originally, I have read the German description first. And there it is a little bit more clear that the proximity detection starts at a distance of 50 - 70 cm.

I am working on a project "car with trailer". I tried to have the beacon on the trailer and IR sensor on the car's back side. But I failed to get trailer's orientation with this setup.
Actually, I found a tricky way with the light sensor to measure trailer's angular.

Cheers, Jürgen

[inxt-generation]

Just a note about the beacon - it uses the same protocol as the Power Functions IR remote. The two sticks on the PF remote send the same signals as the up/down buttons on each side of the remote. Any signal coming from the correct channel will act as a 'beacon' for the IR Sensor. Basically, the only functional difference is that the EV3 beacon has a toggle beacon mode and fifth button.

[philoo]

Ah - interesting indeed! So we can actually use any PF handset with permanently activated button as beacon... (but perhaps there are IR beam width considerations?)

[tabbycatrobots]

Thanks for all the ideas. Regarding distance in beacon mode, I've found that 2 m is about the limit with
fresh batteries. And with just one beacon turned on, the robot is pretty good at stopping at about 15 cm
away, per my program, give or take a little from run to run. With multiple beacons, even on different
channels, the proximity doesn't work. Talking to a friend, who is an engineer, he was not surprised by my
description, saying IR does reflect all over from almost any surface, open to interference, and thus not easy
to use. He added that some open cell foam is a poor reflector. I got some foam with which I'm going to
line some corrugated boxes, to make some IR black "caves", and put a beacon at the rear of each cave.
I'll post any results. Regarding interference using the IR sensor, it doesn't work outdoors in the sun.