Light Sensing Robot

[billbo911]

Originally Posted by sparksandtabs

to test my programming skills with a PIC(when i get it) i was gonna make a light sensing robt, to go to the brightest spot, or the darkest, but i dont know how i would sense the light, i could use a photoresistor or photo transistor but that would measure the like where the sensor is not out away from it

for example if the robot was in the shadow outside it would sense the shadow not the sun light

Here are some suggestions:

1) Use two photo resistors facing the same direction, separated by a piece of foam a couple inches long, or anything else that will block light. Measure the difference between the two cells to determine which side is brighter. Adjust your steering to go toward the brighter side until the values of the two cells are equal (within a certain window or dead band). This will allow you to steer toward light.

2) If neither cell is seeing enough light to determine which way to steer, like your shadow scenario, set the program to run a searching pattern. A spiral outward works well and is simple to implement.

Both of these suggestions will take some experimenting to find what values work well. Photo resistors are notorious for not being matched, so you should grab extras to sort through to find a set that are close. Then you may need to build a custom circuit to give you a real good match, slightly modifying the resistance of one leg over the other of the sampling circuits.

Oh Bummer. Alan beat me to the punch while I was typing.