Line folower without motor driver IC

Hi Folks,

I am trying to make a line folower but I am having two problems:

First i have a sensor array: A pololu QTR-8A, however I cant find any source code using this model?

The second is that i would like to get the code working with two transistors to control each motor. Most of what i seem is controled with a L298 and my local maplin doesnt stock these, so it would be much easier to use only 2 mosfets. I dont need reverse.

Any advice?

Regards

http://www.robotroom.com/BipolarHBridge.html http://playwithrobots.com/robotics-pool/motor-driver-circuits/dc http://www.laurentkneip.de/H_bridges.html http://www.instructables.com/id/H-Bridge-on-a-Breadboard/step2/H-Bridge-Theory/ pololu QTR-8A (LIBRARY)

Hi,

I am not looking on how to build an H bridge, in fact for several reasons I want to avoid one and use a single transistor to PWM the motors in forward direction only.

I do, however, have a concern: Does the PID actually need reverse to stop the motors or is this completelly optional, just in case the designer plans to add reverse to the motor?

I am also a bit confused on how to use the library. basically at the moment I initialize the pins and read the digital input (filtered by a LM324)

Thanks

You can get away with using a single mosfet per motor if you are only going forward. However, make sure you do something about the voltage kick whenever you turn the motor off, or you'll fry at least your MOSFET otherwise. PID should work going forward only, at least for speed control. Distance control is another matter, and would be greatly helped by being able to reverse.

Does the PID actually need reverse to stop the motors or is this completelly optional,

What PID ? (PID stands for Proportional Integral Derivative, feedback loop) Does that mean you are going to implement a SW PID or do you plan to use a HW PID to drive the motors ?

Thanks.

The idea is to use a mosfet with associated flywheel diode, as the voltage drop of a H bridge is tipically about 1V, which makes a significant difference when operating on a single lithium cell.

I also have a problem, that when I stop the motors it tipically moves a bit on the direction where it was going and this is causing me stability issues. Sometimes it simply loses the signal.

As far as I know I could just add another mosfet to "short" the motor, but seems that giving it a reverse voltage seems to be the norm. Can someone comment the advantages of both aproaches, or how to make it manageable without any braking at all?

Kind Regards

Does the PID actually need reverse to stop the motors or is this completelly optional, just in case the designer plans to add reverse to the motor?

What PID ? Do you have a PID motor controller ?