Our team ordered some of the Pro-Gaff “grey” tape that is listed in the game manual as the tape that will be on the tracking line. Unfortunately, when we tested the sensor on it, there was absolutely no difference in reflectivity between the tape and our carpet. We have read from FIRST that we should just use something shiny for testing and then recalibrate at the competition, but have any other teams had this experience with grey gaff tape? The tape does not look at all reflective to the eye.
This was my experience as well. Official gaffers tape on unofficial carpet didn’t have enough contrast regardless of mounting height. Actually, our office has two colors of carpet intermingled, and it worked fine on one and not on the other.
My solution was to overlay the clear packaging tape over the gaffers tape. This upped the tape reflectance in the IR range so that it was easy to distinguish from the carpet.
As long as you get there to be a line of high contrast material, it doesn’t matter whether you use shiny overlay, different carpet, or different tape altogether; as long as it allows you to distinguish and program the robot to drive it, then at the event on Thursday, you can calibrate for the official carpet and tape combo.
Greg McKaskle
Thanks, we’ll do that. We are a little bit concerned about the mounting height - how can we test how high we can mount the sensor off the ground? We want to mount it above the bumper zone to make it easier to adjust the sensors (so the bumpers don’t get in the way), but we don’t know if that will be too high for them to sense the tape…
The tutorial on ni.com/frc discusses mounting just a bit.
If the sensor gets too close to the carpet, less than a few millimeters, there is not a good return path for the reflected light. As the sensor is raised above a few inches, I saw a dropoff in the sensitivity.
Especially if you are going to tune things at the regional, I’d use the built-in LEDs to get a sense of how the height affects the signal using your tape and carpet, and if you can design it, allow for easy changes to mounting height. I used extra pieces of frame to raise and lower by about 1.5" increments.
Greg McKaskle
We also experienced lack of contrast between the official gaffers tape and the carpet we have. Our carpet is a dark blue with some lighter colors mixed in. We wound up testing with regular duct tape that is somewhat shiny. With it, we got a clear difference. Our sensors are mounted aproximately 3.5 inches high, which might be a little much.
Was anyone able to get the orange led to come on that indicates a 2x light return? Looks that that would be ideal, but I don’t know if its possible with the gaffer’s tape.