Building the Controller

Just like the Sumo Bot, the control system is designed to be cheap and simple, but effective. Unlike other competitions and options that use wireless controller technology, the SumoBots will be tethered. This will keep costs low as the components needed are significantly cheaper than the wireless counterparts, but will also teach a good lesson on simple electronic circuits. The controller uses a DPDT (Double Pole Double Throw) Momentary Switch that is wired creatively to create a forward and reverse for what will be your tank drive-controlled robot. The controller can be built out of any (non-conductive) material that you want. It will also act as the power conduit for the SumoBot to have power in its motors. 

Wiring the Controller

Step One: Follow the Schematic

Looking at the Schematic above you can see that we are making a tank drive robot with forward and reverse using a DPDT (Double Pole- Double Throw) switch as the input from the controller. Each switch will control the direction of each motor giving it 100% power in either direction of rotation when pushed in that direction. These switches need to be hooked up to a DC power source along the common terminals. 

Step Two: Make a Wiring Diagram

A wiring diagram represents the schematic in a more readable way for beginners in electronics and robotics. This diagram directly shows what part is connected to another part. The DPDT switch has six total poles- two common and two throws.  Power will be applied to the common terminals and then dispersed to the throw in the direction that the switch is pressed. The motor is only connected directly to one of the throws so when the switch is pushed in one direction it will go one way, when it is pushed the other way, it will spin the opposite way. 

Step Three: Assemble the Electrical System

Using your wiring diagram connect the pins of the switches using wire. The suggested wire would be 22-28 AWG stranded wire. Stranded wire is a better choice when heavily manipulating wire with repeated bends and moving while building the controller. Solid core wire will tend to crack or snap after repeated manipulation. Depending on your DPDT switch, you will have screws to mount your wires to or will have to solder your wires to the tabs. For instructions on soldering, see our Soldering Page. Since the competition will be using a DC power supply, you will have to attach wired to bolts or some other conductive probes where the power supply is in the wiring diagram. 

Making the Controller

Step One: Start with Paper

Just like we did with the sheet metal profile, it is always best to start 3D modeling with by prototyping. We can do this cheaply and quickly using paper. Draw your surface development on paper. Be sure to mark your bend lines, the holes for any of your switches or buttons, and the holes that will be used for the bolts that will act as your anode and cathode that power your Sumo Bot. Quickly cut out your shape and holes and bend and tape it together. Hold it in your hand to check if you like the size, shape, and position of where the switches will be. If you need to adjust anything, do this now. 

Step Two: Switch to Cardboard or Foam Core

Using foam core or cardboard, transfer your finalized surface development from your paper cutout. Cardboard or foam core will provide you with a stiffer material to prototype with. You could also use any other similar material you have at your disposal. 

Step Three: Bend Foam Core/Cardboard to test fit Electronics

Bend the Foam or cardboard along the bend lines. Because this material is thicker than paper, it will have a higher K-factor than paper. If you use the back side of an X-acto Knife or pen, you can drag it along the bend lines on the inside of the bend. This will pre-deform the bend-line making this material easier to bend along the line. You can see this example more clearly in the steps to build the SumoBot. Use hot glue to connect the edges once bent and add your parts in to test fit. If you are happy with the fit and feel of the controller with all the parts installed, you may move on.

Notice: If you do not have access to a laser cutter/bandsaw, acrylic, and acrylic bender you may skip the following steps. A foam core or cardboard controller will last more than enough time for pactice and a Sumo Bot competition. You can also choose to make a controller out of wood or 3D printing. You can make your controller from any material but you should stay away from metal as it conducts electricity. 

Step Four: Cut Acrylic 

Using acrylic or a sheet of plastic cut the shape profile of your surface development. Be sure to include all the holes you need for your switches, buttons, and bolts. You can cut this using a Laser Cutter or with a bandsaw and hand drill. 

Step Five: Bend the Acrylic

An acrylic bender uses an inductor to provide a heated surface in a straight line. You can use an acrylic bender by lining up your bend lines for your controller. This process is very similar to using a sheet metal brake but softens the material by heating it allowing you to bend it easily. Once you bend it to your desired angle, hold it firmly until it cools and hardens again.

Step Six: Fit the Electronics

After you finish bending your controller, start fitting your electronics, into your controller. Test how the controller fits in your hand and that you can engage all the switches and buttons. If your components are wired, connected, and ready to go you are done. Be sure to fasten the cable between the robot and controller so that one doesn't pull the other out. 

Wiring from the Controller to the SumoBot

Cat-5 Cable is a common cable used for data and other low-voltage applications. Cat-5 cable has 8 wires that are each 24 gauge solid core lines. They are color-coded in pairs and will make the perfect cable for your SumoBot. In general, your robot will need two wires for every actuator (a device that turns energy into motion.) Your SumoBot will have at least two motors for the drivetrain but can have up to two more for other features of your SumoBot. In the past, some SumoBots have even used these connections for flashing lights or buzzers. When working with cable and wire, the most important thing to consider is the current rating that any individual gauge wire can handle. According to a reference from the Handbook of Electronic Tables and Formulas for American Wire Gauge a conservative estimate for 24 gauge, the single core wire has a current transmission is 3.5 amps. With the design constraint that the SumoBot competition has of keeping your entire robot operating at less than 1amp of continuous current, the Cat-5 Cable's eight 24AWG solid core wires can handle more than enough current. 

Full Assembly