Switching to Rear-Wheel Drive

I’ve made two versions of the Open Face Sandwich robot to show off the color copper clad boards that I bought. The first version is a front-wheel drive robot with a red PCB. That robot suffered from oversteer.

The rear-wheel drive version has the motors rotated around and a blue PCB.

Rear wheel drive robot with blue printed circuit board

Rear wheel drive robot with blue printed circuit board.

The circuit board has a place to directly solder a small DPDT switch, to change from light-line following to dark-line following. That particular switch does not feature a center-off position to completely disable the motors for debugging purposes. Therefore, I attached a full size switch to the rear of this robot to provide complete functionality.

Rear switch mounted on small PCB Rear DTDT switch circuit

Left: Rear switch mounted on small PCB. Right: PCB circuit.

Spare room on the 4x6 copper clad board allowed me to make the mounting board containing the switch’s wiring out of blue PCB. Having a printed circuit is much easier than connecting the necessary wire loops and soldering all of the wires directly to each lead on the switch.

Battery Snap

I have long preferred a hard molded plastic battery snap rather than the thin flexible kind. Now, I’ve found an improved version the covers the metal connectors atop the battery. The complete covering prevents errant wires, screws, or tools from accidently making contact and shorting the battery.

Nine volt molded plastic battery cap with shroud

Nine-volt molded plastic battery cap with shroud.

This part has wires that come out of the wide portion of the snap, as opposed to the side. The shape is called a “T”. Depending on how the battery is mounted, this arrangement can reduce strain on the wires and can provide a more direct route to the circuit board.

The shrouded battery snap is made by Eagle Battery Holders, part 123-4016-GR from Mouser Electronics.

Color Circuit Boards

I’m really excited about colored boards coming to the market. Hopefully, experimenters and case moders will encourage PCB suppliers to produce and supply a wide variety of colors. Given the volume of electronic devices, and the potential aesthetic and functional value of color coding, it seems like a golden opportunity for PCB manufacturers to offer a selection of substrates.