photoresistor sumo robot

BOB55

Hi,

Im trying to build a mini sumo robot using two photoresistors instead of QTI sensors. I went through all the projects in the Boe Bot project book but none of the programs give me a general program·that i can use for all sorts of light conditions. Can someone please help me with a program or point me in the right direction?
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BOB55

Franklin

What are the parameters that have to be met and which photoresistors are you using (datasheets)? What have you tried program wise? (how do you know they don't work?) How do you have them mounted and where do they get their illumination?

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- Stephen

BOB55

The photoresistors im using are the radio shack ones (http://www.radioshack.com/product/index.jsp?productId=2062590&tab=summary). On my robot they are located on the bottom of the robot thats right on the floor, probalby a millimeter off the ground. I know the programs aren't working because as i went through them, the ones that did work in one location, didn't work in a different location.




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BOB55

agfa

Check out Robotics with the BOE Bot starting at page 193.· It references using them in voltage divider circuits as well as in RC circuits and the RCTIME command.· ·http://www.parallax.com/Portals/0/Downloads/docs/books/edu/RoboticsV2_2.pdf

Using a light source near the surface you are trying sense will help, such as some LEDs mounted near your sensors to illuminate the surface.

The product you mention is an assortment.· Probably all different, as far as their reaction to light.· If you use a voltage divider·circuit it will have to be adjusted for each individual Cds cell.· And different·light levels will also effect this.· With RCTIME you could compensate for different light levels using some kind of calibration routine.

Cds cells are slow to react to changes, and using RCTIME will slow your program down even more.· I've used IR photodiode pairs salvaged from PC mice for line following with good results.· This is also less sensitive to indoor ambient light.

Hope this helps.

BOB55

Thanks Franklin and agfa.

I·put two LEDs on the bottom and now the program works.
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BOB55