Servo 112004

Motor mount bracket, motor, and wheel showing collect and brass tubing. The stripes are printed on paper and glued to a plastic backing.

Lock washers, lock nuts, and glues will allow the screws to remain tight with their nut. Lock washers are what I use most, especially for smaller nuts. They are available with inside teeth, outside teeth, or split round washers. Lock nuts — either all metal or nylon inserts — are also good choices. Lock-Tite and similar thread locking liquids are available in several choices: permanent, non-permanent, and with various temperature ranges. In a pinch, putting Super-Glue or other CA (Cyanoacrylate) glue on the threads will lock the two together.

Almost any motor used will require some kind of capacitor across the terminals. This capacitor will reduce the noise that may be induced into the computer. Usually a 0.1 or 0.01 |j.F capacitor connected across the motor terminals will do the trick. If the robot doesn't seem to work after a while, check the capacitor; it may have broken.

On the bottom bat, I added some additional sensors. I mounted two CdS photocells, a servo with the Polaroid ultrasonic sensor, and a light source

Top view, showing VELCRO that holds the Handy Board, the compass, and the wiring through the top.

Top view, showing VELCRO that holds the Handy Board, the compass, and the wiring through the top.

along the front. I also mounted a barrier strip in the rear. The chassis was a little wobbly, so I found some furniture skids from the hardware store and put them at either end. For the front skid, I put some black conductive foam to act as a spring and damper. I used the plastic cover that came with the skid to keep it attached.

Mounting the Polaroid ultrasonic sensor was a challenge. I wanted it on the servo so the robot could "look around." I used the servo arm that came with the servo to attach to a piece of 1/8" plastic. The threaded screws that came with the servo were self-tapped into the plastic. I then mounted a project box on this piece of plastic using 4-40 screws. The project box was cut out to mount the ultrasonic transducer and the board was mounted inside. The transducer was attached to the box using clear silicon adhesive.

Once everything was attached, I screwed the long stand-offs on the bottom using the 8-32 countersunk screws. The top was attached using the same 8-32 countersunk aluminum screws. I drilled large holes in the top, near the center rear for running wires from the bottom sensors and motors to the top where the computer will be mounted.

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