21 Feb 2006 cschur   » (Master)

Hi all,

A very busy week for the Geobot, we added two pwm processors to the drive train and can now do something other than full on and full off on the track drive. Our test was to do a S curve, something not easy with a tank tread drive! Anyway it works fine, and now we can do any type of turn we wish to avoid large trees and rocks or home in on a distant target by simply veering one way or the other.

Our PWM drive was done this way: Both motors are driven with the dual L298 motor driver from Solarbotics. the Enable line is the PWM input, and the other two inputs provide the direction for the H bridge.

What we did was drove these inputs with a 16F628 PIC we programmed to accept a serial data stream at 9700kb on its input containing the two direction bits, and a 0 - 255 pwm percent bit. So to go straight for example, I blast off a single serial command from the main processor to this motor driver PIC and it changes and stays that way until we send off another serial command to change it. Set and forget control. If anyone is interested in the hex file for the PWM driver, and want to make thier own free serial to PWM chip, email me.

Were moving on now to the 4 channel matrix sonar array, and have a unique approach to obstacle avoidance tied right to the PWM for each motor, youll like it...



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