My team wants to use a light sensor to follow the gaffers tape on the floor in order to get lined up to place hatches/balls. We’re thinking about using a line follow program like the ones frequently used in FLL. In order to do this, we need a sensor with a readout of percent light reflected, but I haven’t been able to find one. Does anybody have ideas?
I haven’t used it, but something like this? https://www.sparkfun.com/products/11769
My money is on this:
It’s rugged, adjustable, and FREE (from FIRST Choice). What more can you ask?
The Rockwell Automation sensor on FIRST Choice appears to be a digital sensor, not an analog sensor like the OP asked for.
You’re right, but with the adjustment knob I think the OP will find that it’s what they wanted, just not what they asked for.
We used something very similar to that (with an adjustment knob) in 2011 Logomotion to great effect on the lines that field had (it came in the kit even, and we still have those sensors).
This looks like what I was looking for. It looks a little on the cheap end, but it can’t hurt to try!
How would you suggest programming a line follow with this? I believe we have these sensors, but we’ve used them for proximity in the past. To me, the advantage of an analog sensor is that we could just use one, but I think you’d need to use at least two of the Rockwell ones. Or is there another way?
Sure, you could use a light/color photo sensor for tracking the line, but you don’t know how close you are to the line.
The logic would be: If the sensor is reporting false, turn the robot until it lines up, and then track, rinse, and repeat. A better approach would be to use a vision camera.
A cheap alternative for vision tracking would be the Pixy 2: https://www.firstchoicebyandymark.com/fc-pixy2
We have used the limelight in the past, which is great and easy to setup. But the compromise is made in price, at $400. https://www.firstchoicebyandymark.com/fc-pixy2
If you had a vision camera, you could get a number that would say the robot is exactly 0.8f away from the white line center, and you could tune driving better.
Thanks! The Pixy 2 looks practical and relatively cheap. We do have a vision tracking camera, but we’re not totally certain we can keep it safe on the underside of our robot.
Yes, what you need to decide is whether or not you need absolute precision, or if what you need is, “I’m pretty close.” Just like Christopher149 said, sensors similar to the Rockwell ones were used in 2011, and teams did fairly well tracking lines on the floor with them. The Pixy is an alternative, for $$$ and complexity. You need to determine just how precise you need to be, and if you’re actually going to make use of all that precision.