Servo - July 2009

involve other “cable” management devices. You can get plastic clamps of various styles and sizes that are designed to hold bundles of wire and cable together. A single eyelet is used to anchor the clamp. Use a large clamp for round-case motors, and secure the clamp in place by drilling a hole into your robot’s base; secure with a nut and screw. Use a clamp on each end of the motor to keep it stationary. Depending on your goals, design, and the weight of your motors and other parts, you may also find a thick rubber band to be a useful fastener. If you can’t wrap the band around the object that you want to secure, thread the ends through holes in the base and then use wire twist wraps (the kind they use in grocery stores in the produce section) to keep the band taut and in place. The disadvantage of this method is that you may need to make fairly large mounting holes in the base in order to accommodate the larger thickness of the rubber band.

Toys and Household Materials

I’m far from the purist and don’t mind reusing things like LEGO bricks in my prototypes. Construction toys

are excellent sources of cheap and reusable parts. One method you can try is using LEGO extras and discards for making customized accessories.

The snap-on nature of LEGOS allows you to easily reuse them for different prototype projects. Glue (double-sided tape works too) some LEGO plates onto your base and then use Technic beams and other LEGO parts for attaching things to the plates. For example, you might glue the flat bottom of a standard R/C servo motor to some LEGO blocks. (It’s okay to use glue here because you’re able to re-use the motor as much as you’d like, because you can simply pull it off the LEGO plate when you’re done.) Use the servo motor to quickly and effortlessly attach a sensor turret to your base. Just add a bracket and ultrasonic or infrared sensor on top of the servo, snap the servo into place on the base, and you’re done. The same concept works for other components as well, such as compass-es, accelerometers, microcontrollers, speakers, lights, you name it. The idea is to mount the part to one or more accommodating LEGO pieces, ensuring that everything is aligned. This allows you to press one LEGO part into the next.

The idea doesn’t stop with LEGO

Art Supply.com is an online source for sheets of foam clad board, corrugated plastic, and other materials useful in creating robotic prototypes.

beams, plates, and other parts. You can also use plastic or metal construction set pieces from an Erector Set. One benefit here is that if you make accessories using these parts, they are easily transferred to full robots once you have successfully prototyped the design. For instance, you can permanently mount a short Erector Set beam to a servo motor and use it as a mounting bracket for a cardboard-based prototype. Use screws to secure the bracket to the base. Once you have everything worked out, simply remove the bracket from the cardboard base and re-attach it to your robot’s permanent base. Finally, be on the lookout for common household items that can be repurposed for quick and easy robot protos. The ubiquitous Popsicle stick — sold in bags by the hundreds in craft stores — is a good example. Use them to make temporary bumper pieces for your robot, or stack them and poke or drill small holes in them to make mounting frames for your electronics.

You can also use small plastic jars or cut-up water bottles for housing speakers, buzzers, LEDs, and other small parts, plus, the caps of water bottles for undercarriage “skids” (for two-wheeled robots). Remember: The idea isn’t to make a permanent robot that will withstand hours and hours of experimenting, but something that will hold together long enough for you to find the bugs in your design, and make it better.

Sources

Online is a great source to find items such as laminated foam and plastic, but shipping can get expensive because of the size. Check your local home improvement or hardware store, as well as most well-stocked craft supply stores for things like foam board or corrugated plastic sheet. If you can’t find what you need locally, try out some of the resources here to use in your next robot prototype.