Color Sensors

[wilsonmw04]

Does anyone have any experience with color sensors? We are looking at ways of controlling the length of belts and bands by placing colored or reflective tape at stop and start points. We have never used sensors outside of the KOP. How can we make sure what we get is compatible with the control system FIRST uses?

[Molten]

I used color sensors for a marble sorter for PLTW and hated it. I never got mine to work. Good luck and hopefully the next person will have advice on the matter.

[seanwitte]

If your belt is a uniform color then you can use contrasting paint to mark a line and sense is with a photoresistor. An example is a white line painted on a black belt. There are tons of examples online for line-following applications. The circuit uses a photoresistor or phototransistor in a voltage divider. To make it even easier you can get a pre-packaged unit like this:

http://www.acroname.com/robotics/par...E-LINE-IR.html

[Alan Anderson]

Originally Posted by wilsonmw04

How can we make sure what we get is compatible with the control system FIRST uses?

If the sensor provides an analog signal from 0-5 volts, the RC analog inputs will accept it without problem. If the sensor provides a digital signal of either 0 or 5 volts, the RC digital inputs will accept it without problem.

The kit of parts in previous years included optical sensors from Banner. The output was an "open collector" transistor circuit, essentially a contact closure to ground. The RC digital inputs have an internal pullup resistor to +5 volts, so they work with that type of sensor without problem as well. (That's what this year's Gear Tooth Sensors provide.)