Society of Robots - Robot Forum

yeap, you got the right idea. its 99% correct.

two comments . . .

when gathering initial sensor inputs, put a button operated pause in your code:

cin>>left_sensor_white;
cin>>left_sensor_black;
while(button=0);//wait until you move robot so sensors can see other condition
cin>>right_sensor_white;
cin>>right_sensor_black;

when you determine your threshold, assuming you are using an 8 bit ADC, rewrite it as this:

th_r= right_sensor_white/2 + right_sensor_black/2;
th_l= left_sensor_black/2 + left_sensor_black/2;

it means the same thing, but avoids 8 bit int overflows.


there is one flaw in the autothresholding code that you will probably not encounter -> if the ambient light changes drastically after calibration (such as clouds blocking the sunlight coming in through the windows of the room you are in).

also, since blue contrasts really well with a white line, you may just want to use differencing code, meaning that if two similar sensors get two very different readings, you can assume one is on the line and the other isnt. this removes ambient light problems. the thresholding method works best for 1 or 2 sensors, while the differencing method works better for 3 or more.

this method ignores ambient light, but you need at least 3 sensors for it

do this pseudocode as a loop:

store each sensor value in an array
array = [sensor1, sensor2, sensor3, sensor4, sensor5]

now find the maximum and 2nd maximum value of these equations:
A=sensor1-sensor2
B=sensor2-sensor3
C=sensor3-sensor4
D=sensor4-sensor5

(a maximum means a line edge is detected there)

lets assume B and C are the highest -> that means the line is between B and C.
if the highest were A and B, that means the line is on the left, so you need to turn left.
etc.

its basically edge detection with photoresistors.

as for the ambient light problem
suppose its dark in a room and your robot runs the thresholding algorithm. now your robot goes halfway down the course, then suddenly really bright sunlight comes in the windows -> the thresholds now become invalid and your robot starts attacking kittens 

waiting for the answers please -_- 

thanks alot
 
i will try it and will tell ya the results , hope it works with the blue background .