Poll: what sensor for pooper?

[Illyana]

If you want to use vex light sensor with flashlight for ball color detection, you gotta read this first:

LDRs, LEDs and the color of VEX field tiles

Part 1. One of the long term items on my “to do” list has been to get hold of a VEX light sensor and see how suitable it is for detecting colored objects, specifically the color of the alliance starting tile. Before jumping into that I’m going to deviate a little into some basic color science that needs, at least partially, to be understood so the behavior of the light sensor is a little clearer. As you all know from high school physics, visible light is part of the electromagnetic spectrum w…

@jpearman

So that was an awful lot of technical information to arrive at the conclusion that many of you probably know already.

Use the VEX flashlight with a red filter over the light sensor I would also turn the flashlight on and off under software control and look for a difference in the light sensor output. This should help eliminate effects due to additional ambient light that may be present at some competition venues.

Color Sensor

Yes but if you use a color filter it should allow you to detect the amount of a certain color A nice explanation: http://scienceblogs.com/dotphysics/2010/05/04/how-do-color-filters-work/ Disclaimer: I’ve never actually used color filters. I prefer just to use jumper clips to set different settings rather than rely on the robot’s calibration, which can sometimes act funny in different competition lighting.

Color Filter

Last season I had two light sensors right next to each other- one standard and one filtered with yellow tape- and compared the values given by the two to identify cones. It worked well (as long as the cone was right up against it of course). Because the tape absorbs most non-yellow light, the closer together the values of the two sensors are are, the closer the light is to the color of the filter. I don’t know the exact brand of tape I used (I’ve had it for years for electronics work), but here …

Sacramento State Management & Venue Problems

Hey everyone, Last weekend, my team, 5776A, participated in the VEX Sacramento State Championship, which we’d been looking forward to ever since we qualified in November. Honestly, after over 3 months of meeting every day working on driver practice, tuning our programming skills/autons, and scrimmaging with local teams, we felt like we were ready to compete at our best and beat our previous skills score of 43. Sadly we found that this wasn’t the case. Our robot uses 3 line sensors, two to dete…