Technical Specs of Vex Line Sensor

For our project we are attempting to use the Vex Line Tracking Sensor’s IR sensor to detect other IR beacons placed around a border. However there is an issue: We can’t trip the sensor. Nothing is working: Remotes, IR lights, even the other Line Tracking Sensor.

What are the specs of the sensor? IE frequency or some other known item that can trip the sensor? Has anyone successfully been able to do this?

Thanks in advance

IR Sensor?

Are you referring to this?

If so, it is a light sensor, not an IR sensor

If you are reffering to the Line sensor which IS an IR sensor that contains both a transmitter and receiver, then the technical specs are on this page and here

He said “Line Sensor” so I think that’s what he was referring to…

oops Misread it - thanks!

The Line Sensor is a self contained unit with it’s own IR source. Any other IR source you try to add to that will simply interfere with the operation of the sensor.

When you say “interfere”, do you mean I will be canceling out the transmitter (value of 0) or will just add more (very high value)?

The IR detector is looking for IR energy of a certain wavelength and pulse rate.

By adding a second IR source, you may overwhelm/saturate the IR Detector and make it unable to detect the signal it is looking for.

For example, suppose you are looking at a light bulb that someone is blinking on and off with Morse code. In a dark room you could easily see when the light was on and off and decode the message.

Now have them put that blinking light bulb in front of the sun. Can you still tell if the light bulb is on or off?

Or, suppose you put that blinking light bulb in front of another blinking light bulb. How do you tell which one is on and which one is off?

That is what you are doing to the IR sensor when you add a second IR source - either overwhelming it or confusing it.

Since I really need this as a feature, can we just open up the sensor and put tape over the transmitter? I really don’t see any other way to read IR data because all the connections are proprietary.

Or maybe I have this all wrong. The goal of this was to be able to put IR transmitters around a border on the ground. The robot would autonomously/blindly go around until it got close to the sensor, sense that it’s close to the border, and turn around. We didn’t want to put up large pieces of wood or program a fixed path, we just want it to bounce around inside of the border. Is there another way to accomplish this?

Thanks for all your help

Sure, Just put a ring of white or black electrical tape around the border and use the line sensor to detect it - that is what it is intended for!

This would be faster and cheaper than trying to rig a bunch of IR transmitters everywhere (you would nee a lot)

That would work fine if it was on a flat ground surface, but this particular robot doesn’t operate on tile floors, it operates on grass. I know, its weird, but that’s what were trying to do. And were trying to define the border subtly. A nice large white tape I guess could be used, but that’s not subtle at all and detecting it is going to be hard among the grass.

Dig a trench, then use a sonar sensor to detect the depth … sorry - I’m running out of suggestions …

Hmmm… wanna try something really different?

Connect the antenna of a 2nd transmitter to a really long wire. Simply lay that wire out along the boundary you want to detect.

Use the 2nd receiver port to detect that energy (You’ll have to press one of the buttons or joysticks periodically to generate a signal you can recognize in the processor)

Take the 2nd receiver antenna (the yellow wire) and wad it up so it is REAL inefficient. Maybe hang it under the robot. Now the processor will only see that signal when it is close to the long transmitter wire and can react accordingly.

It’ll take some experimenting, but could work if you set it up right. Plus it is easy, portable and cheap. If you can bury the wire - even better.

How about that?

How about:

  1. Obtain a docile squirrel
  2. Train it to pace the perimeter, staying as close as it can to the robot
  3. Train it to poke a bumper switch on the robot with its nose whenever that switch is in reach.

Less flippantly:
A variation on the idea rfolea just suggested: Obtain one of the “electronic fences” sold for keeping dogs in yards and build an interface between the collar and the robot.



Never thought of that. There are some issues (power, dragging a wire…) but we just might be able to solve them.

Thanks so much people for the help! I really appreciate it. I’ll post again if I run into any more dead ends.