Robotics - Motor Drivers and 3rd "Wheel"

Intro | Update 1 - Motor Driver & 3rd Wheel

To conserve room on Bob, and to keep things simple to start, I've decided to switch to the PIC 16F628A. The reason being - I don't need variable speed all that much. Later when I get to the point where I want to program "moods" into him, I'll upgrade to a 16F76.

For Bob's motor driving circuitry, I decided to use 2 x TC4424 (Microchip) dual Mosfet drivers. These babies operate on 4.5 to 18 volts, and can handle 3 amp peak currents (I measured Bob's motor current at about 700mA stall current, at 4.5 volts). They are driven directly from the PIC via two logic inputs. I ran a simple test program, making Bob drive around on a programmed path for a couple minutes, and the TC4424's weren't even warm.

Unfortunately, this programmed test-drive revealed a problem. I miscalculated the third wheel's sideways-sliding resistance, and it tends to grip the carpet rather solidly.

Tommorrow I'll drop by a hobby store and see if I can't find a large, polished-wood or plastic beat, instead of the unidirectial roller.

 

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