Servo - January 2007

the robot’s left. I

^FIGURE ¹⁴^._Project _boxused self-tapping after cutting screws and some hot ^{large hole}glue to hold them ^{for cable.}both in place. The BOE was mounted inside the hinged lid opposite of the robot’s back (see Figure 15).

Breadboard Layout

FIGURE 13. Project box with Dremel™ cutting the plastic like a hot knife through butter.

If you do not have precut holes or you want to run cables in a different way, follow the hole cutting procedure outlined here. Measure and mark the hole on the bottom of the box. Be sure to make the cut big enough for the connector to pass through.

You will want a hole cut for the ribbon cable, DB9 connector, and two switches. I decided to cut the hole for the ribbon cable on the bottom of the box, the hole for the DB9 on the side, and one on the top and the other on the side for the switches.

I used a standard cabinet hinge for the project box. I like to use a hinge because I know I will return to the robot to hack and hack again. If you are planning on very little modifications, you can use the standard screws to close the box and

leave it that way.

The best way to cut holes in plastic that I have found is a Dremel™ type hand tool with a metal striated bit. With the bit spinning at high speed, the friction heats the plastic up and it cuts like a hot knife through butter (see Figures 13 and 14).

Mount the BASIC Stamp and Parallax Board of Education

Place both of the L293D motor driver chips (quadruple half H drivers). Place the 74HCT164 shift register chip.

Starting at the top of the breadboard, place the first L293D centered on the breadboard. The top of the L293D (pin 1) should be in the fourth row, and be sure the other chips have three holes (rows) between them. Place the 74HCT164 shift register last (see Figure 16). Follow the schematic and photos in Figures 15-17 for details of component placement.

FIGURE 15. Back of Roger showing the terminal block on the upper left, breadboard upper right, and BOE lower center.

Place the Board of Education (BOE; see Figure 2) or your microcontroller board of choice into the project box. Make sure it will fit before you start drilling holes. It is best to mark the holes inside the project box so you know were to drill before you start.

Doublecheck to be sure all of the holes match up, then start drilling. Use a bit that is smaller than the self-taping screws so the screws will have something to grab onto when you tighten them. Place the stand-off spacers on the holes, place the BOE on the spacers, and drive the screws through the BOE and spacer to secure it to the inside of the project box.

Inside the box, I mounted a standard breadboard on the robot’s right side and a terminal block on

Terminal Block and Breadboard Layout

Pick a terminal block that you like and be sure it will fit inside of your project box. In Figure 18, I used the one in the upper right hand corner.

Number the terminal block 1-15. Solder the ribbon cable wires to the terminal block according to the Cable Pin Connection Chart in Figure 11. On the other side of the terminal block attach the lead wires for the breadboard in the order in Figure 19. Use wire markers or masking tape and a pen to number the wires near the end that plugs into the breadboard. My breadboard came with two columns, then a space, five columns, a gap, five more columns, a space, and two more columns. I used the first two for the Ground buss (G1 and G2). For this chart, “G” stands for ground and on the breadboard it is the first and second column. I numbered the next 10 columns 1-10. The last two columns are numbered P1 and