Budget Robotics (Base on a Budget)

Sometimes building your own robot is easier said than done. It can be easy to visualize what we want but then to actually build it can be more difficult or in some cases seemingly impossible. Other times it is more a matter of not having a budget for the entire robot. Spare parts can be found in a number of places and different people have different interests in specific microcontrollers so I won’t focus on that in this article. Instead the focus here will be on getting a usable robot platform built on a minimal budget.

The Drive Train

The drive train determines how the robot will move so that is the first thing you should decide on before getting started. Wheel robots are the easiest to build and often the simplest to control in terms of movement so that is what will be used in this article as an example.

Parallax Inc offers a Motor Mount and Wheel Kit (#27971) which was used in this article (sans wheel encoders) but you can use any type of drive motor and wheel combination to achieve the same results as you will see in some of the examples.

A Wooden Robot?

Why not? When we think of robots, most of us probably wouldn’t think of wood. We would visualize a metal robot or even plastic. But wood has several advantages for the budget hobbyist over metal and plastic. For starters it is cheap. You can get wood for a robot from any hardware store and an inexpensive saw to cut it if you don’t have one. It is durable and also lends to using wood screws instead of nuts & bolts to secure parts. This can further reduce the cost of mounting hardware. It is also easy to cut into the shapes you need without requiring special tools or a mold.

This robot is built from several pieces of wood shaped into a kind of box. Everything was held together using sheetrock screws and the accessories such as wheels were attached using wood screws. The total cost of the wooden chassis including hardware and tail wheel was $10.00. The wood was pine, the tail wheel was a generic caster wheel and the hardware was a handful of screws all purchased from a local hardware store.

Two Parallax HB-25 motor controllers (#29144) are being used to control the motors in this robot. Power and signal wires are routed through holes in the top to a BASIC Stamp 2 on a Board of Education (#28850). A 7Ah sealed lead-acid battery was salvaged from a radio controlled tank project and used for power and for testing, a radio was salvaged from a crashed R/C plane to allow for selective radio control of the robot. You can see a video of this robot in action here. More photos can be found here.

Moving Up To Aluminum

When I finished the wooden robot chassis, I posted it to a thread in the Parallax Support / Discussion Forums where members were talking about creating a robot chassis for the wheel kit, which at that time had not been released yet. The thread is 15 pages long at the time of this article and led to the robots discussed in this article.

Some of the feedback was related to creating a metal chassis and I had already considered what I thought to be the ideal platform in my mind, though I had not yet built it. Parallax Forums member MarkS rendered my description into the image you see here. While this was what I wanted to build, I too was constrained by both a budget as well as the need to create something easy to build.

I finally decided on a square frame and the results can be seen in the photos above. This robot chassis was built using a single piece of 1” aluminum square tube (1/20” thick) obtained from a local hardware store. The tube was cut into four pieces measuring 11-1/2” long and two pieces 12-1/2” long. The pieces were held together using right angle brackets and some screws. The only tools used were a hacksaw and a drill. The hardware consisted of a handful of nuts, bolts and washers and this time two caster wheels were used bringing the cost of this chassis to $20.00! Still very modest, and the same type of motors and wheels were added, but again, any surplus units will work as well. Once the chassis was built I added a top deck and installed some HB-25 motor controllers. Next I decided to add a BASIC Stamp 2 Microcontroller, PING))) sensors and a battery for some simple roaming. More photos and information can be found here.

From Wood To Metal And Back Again…

One of the great things about a tight-knit robotics community is that you always have a large group of dedicated hobbyists willing to share their thoughts and ideas. Many post pictures of their completed work and some of the ideas that were spawned in the aforementioned thread include the following robots.

This is Big BoE and his even bigger brother by Brian_B. You can find more information at the bottom of this page.

Ken Gracey of Parallax shows how even plywood can be used as robot base. More information can be found on this page.

Ken’s robot gained much interest and forum member Tom C created his own version and later added a second deck. One thing you may notice about the 2-deck version is that Tom used threaded rod for the standoff / spacers. This proves that you really can find a lot of good solutions at your hardware store. More information can be found on the pages here and here.

Build Your Own Wooden Robot

This plywood robot was a concept robot that Ken Gracey built to show how useful plywood could be in making a robot chassis. Ken recently refined his wooden platform using additional Parallax hardware to accent the wooden base. He even added CCFL tubes and special machined PING))) mounting brackets. The revised design is shown here. By request of the Parallax forum community Ken is making the DXF drawing of this robot base available free to all. You can download the DXF file from the Servo Magazine website or from the attachment below.

Final Thoughts & Additional Resources

Robotics can be expensive or it can be done on a budget. I have seen robot bases made from balsa wood, plastic pill bottles (solar bots), a mailbox, a toaster, a garbage can, a wheel chair and even from recycled toys such as radio controlled tanks and cars. Once you have the base, adding the electronics is next step and varies based on your microcontroller platform. This forum thread and this forum thread have more custom robot examples and information.

Examples of other robot platforms can be found here on the Savage///Circuits website. Challenge yourself to make something out of recycled parts and don’t be afraid to add accessories to your robot that are recycled from other toys / products. One common accessory to recycle from toys and add to robots is Nerf® missile launchers.

Resources

Wheel Platform Robot – Project

Discuss this project on Savage///Chats

This article was published in the February 2010 issue of Servo Magazine