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Line follower project

Hi guys, I'm working to build a linefollower robot to compete in both linefollowing and maze solving contests, but I've a few questions and problems I hope you could help me resolve.


Well, the first problem are the motors. At the beginning I was using two 3v - 6v motors and this worked fine, but I had to duplicate the H-Bridge chip on my Picaxe 28X1 Started Pack due to the high amperage they required.

Now I need a more accurate speed control, so what would you do? Could I use two brushless motors with two ESC controllers on my board instead of PWM? I think this would be better because it would only take two output pins instead of the four required with the L293D. If this is better, what do I have to do to make them work? I've understood that they use a regular servo signal to work...

And the last question about the motors... Do you recommend me any particular brushless motor? To make an idea of the weight and size of my robot, it's like a slot truck but a little heavier because of the batteries and other robotic stuff.


The second problem is that I may need another kind of batteries of a higher voltage to run the motors, because now I'm using the 3x4,5v baterry pack that came with the starter pack, so my question is: If I replace them for a 11.1v Li-Po battery, would you use one voltage (5v) to run the PIC, another one (6v) to run the servos and the 11,1v to run the motors (powered through the ESC) or only one to run both PIC and servos (5v) and the 11,1v to run the motors? If I do the last thing, how can I take that 5v out of 11.1v?


Well, that is my last problem. At the begining I wanted to build a linefollower module with 6 CNY70, but recently I found an 8 reflectance sensor array on Pololu that could be better than that and there are two different versions, the analog one and the digital one. I want to use the digital one, but I don't know how because the Picaxe board only has 4 analog inputs, so is there any solution or I will have to buy the digital one? If you know any other kind of sensors that would be better just tell me...


I thinks that's all. Thanks for your help!!

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Well, I will look on the other post and see if I can find a good solution... if not I may use the digital version or perhaps I buy a Picaxe 40X2 chip, which has more ADC input pins, but I've to think on that...

And what about the other questions? Any suggestion?

Faris's picture

Check out Tamiya Planetary Gearbox. http://letsmakerobots.com/node/3106?s=l

Faris's picture

I use these http://www.pololu.com/catalog/product/1134 for edge avoiding.

They are extremely sensitive to dark colored objects.

I found that out when I was testing my robot, It detected the Picaxe programing cable as an edge and moved backward. That was bad news for me because the robot wouldn't function well on a dark surface ( it will think its flying :) ).

These sinsors can detect a thin black line easily, I am going to use them for my next robot ( A line following ).

But how will I get the readings separately? I mean, if I could light the sensors one by one I would be able to read them separetely, because the ones connected to the same pin would return nothing, but this is not possible, because the Pololu board only let you decide to light all the sensors or none of them, all at the same time...

I don't know if this is possible, but if I could separate the power of the sensors in two different lines, it would be possible to take the readings in two times, using the 4 ADC pins on the board and powering one line first and then the other one, but I think this is too difficult to do, because I would have to solder on the sensor's board an all that...

Somebody was talking about these in a previous posts. Type "Pololu QTR-1RC Reflector Sensor with Digital Output" in search and read up on that users complaints on which model is better or how to decide..........Good Luck.

Faris's picture

Yes, I posted that, and I stell don't know how to use them.

Everyone argued which way I want to use it and froget about my question :(

I guess I will have to post again.


I've connected 3 Sharp GP2D12 sensors to one ADC channel before and all 3 worked just fine and succeeded like a Fool because I'm Cool like that. You gotta get crazy with this crap and you'll be rewarded. Usually if it's not recommended, I recommend it..............

That looks good, but I would like to have the 8 sensors... is there any way to 'join' the Pololu pins' signals and send all the information to only one ADC pin like the Lynxmotion Line Sensor does? Maybe some type of multiplexer or something like that...

You gotta get High on PortC. Or you could always buy the Lynxmotion Line Sensor.