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Question about a line follower!!!

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auto_mitch

New Member
Hi!!!!
i would like to built a mobile robot with a microcontroller.
The robot will follows a double path (something like circle) which consist of two dark lines.
The 2 dark lines crosscut 10 times from the beginning of the path to the end.
I would like the robot to recognise the crosses and at the first round to go only at the right
ways(between two crosses) and at the second round to go only at the left ways!!! I dont know if photoresistors work as sensors to recognise the crosscut!!!
Any ideas???
Thanks for your time!!!
 

spock

New Member
I built a Line follower some time ago. It was programmed for following a dark line in a light background and it was able to recognise crossings and decide which to take.

I used an easy PIC16F877. They are cheap and easy to programm.

For detecting the line I used a CNY-70 sensor. It is a photodiode in infrared region and a photo-transistor. The both are toghether encapsulated and work perfectly. So you must not bild your own sensor, which is quite complicate and gives a lot of problems.

You can use a DC Vcc for the transmiter and then detect also DC amplitud in the receiver or if you want to avoid the effect of ambiental light you can transmit a modulated signal of some khz and then use a filter in reception. Anyway the receiver has an small optic filter for ultrared and it is no so sensitive to light, I used it without modulation and it worked perfectly.

You should use at least 3 sensors for detecting the middle of the line and the edges but it works better if you make it with more (5 or more). Anyway I tried an edge-algorithm detecting the edge of the line and with 3 sensors it was enought and the robot was quite fast.

For motors you can use even Servos from RC-autos they are quite fast, cheap.


good luck.

david
 

jh001622

New Member
i agree with spock regarding the number of sensors used, but i think three is enough for that kind of track... :D

regarding the right and left line, if they are identical (color, texture and all), i really don't know if you can do it without programming it.

from what i know, you can only use the sensors to turn left or right and program the microcontroller to shift the other line after a number of shifts in the state of the bot. (count the turns until it completes the track)

hope this helps... gluck!
:p
 
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