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Lower section: wheels, motors, batteries, motor controller, and wheel encoders.

To the right is the bottom of the robot.  I used 4.5 inch airplane wheels and electric screw drivers for motors.  The caster wheels are for balancing the robot.   U clamps holds the motors in place.

To fit within the Fire Fighting contest 12 inch maximum, I had to cut down the screw drivers and remove any unnecessary parts.   The ends of the screw drivers actually fit inside the wheel to make sure we were within the 12 inch width.

The silver on the inside of the wheels are the reflectors for the wheel encoders.   The reflectors are automotive pin stripes that have self adhesive backing.   The black wheels with reflective silver pin stripes worked well for encoding.

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This is the top of the lower section looking from the back with the middle section pulled to the side.

The four AA batteries supply the 5V supply when the robot is on its own.  When sitting on the bench and being tested and programmed (which is 99% of the time), it runs on a 5V supplied by a bench supply.

There is a switch which can be seen in the lower left hand of the picture.  That turns off the power from the 7.2V batteries.

Two 7.2V (14.4V total) racing car batteries supply the power for the wheels and the on board 12V power.

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This is the front of the bottom section.  The two H-bridge controllers can be seen.  This was one of my earlier purchases and was expensive.  But I liked them because of the high power they could take, and also the screw in connectors made it easy for construction and testing.

You can't really see it in this picture, but running down the center is a strip that allows wires to be attached together.  Also, there are connectors that allow each level to be disconnected from the others.  This is important because you will find yourself tearing your robot apart often.

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This is a close up of the wheel encoder.  Automotive pin stripes were used for the reflectors.  The contrast between the black tires and the silver pin stripes was great, thus it worked well.  The pin stripes has adhesive backing and was easy to stick on.  The hard part was the spacing of the stripes.

The U clamps that hold the motors in place play quadruple duty.  They also connect the middle level to the bottom level and they hold the wheel encoders in place, plus hold the batteries with rubber bands.

In future months, I will write articles going into detail the various sub-systems.

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