Introduction: Simple RC Wedge Robot
I have loved Remote Controlled Robots for years and my kids grew up being exposed to them. My son is finally old enough where he can have his own robot to start getting the hang of driving with a joystick. I went with a really simple wedge design and easy to work with components. Just jumping into robot building can be very daunting at first but with a little advice it can be fun.
With this Instructable I intend to show how I built my son's robot and which parts I used. Many other components can be used in different configurations with equal or better results than mine. Be creative, be safe and have fun driving around the house or the arena!
Step 1: Parts List
I bought the majority of my parts from 2 websites: RobotMarketPlace and HobbyKing
On/off switch - $1.59 - 1x
BaneBots 2 7/8" wheels - $3.00 - 2x
BaneBots Hex Hub - $4.29 - 2x (the hub needs to have an ID to match your motor)
Beetle B16 Gearmotor - $29.99 - 2x (different gear ratios will give you lots of torque or lots of speed)
HobbyKing 35A car ESC (electric speed controller) - $23.55 - 2
Lipo Battery - $15.00 - x1
Electric connector (XT60 or XT30) - $3.99 - x1
Radio transmitter/receiver - $23.55 - x1
Servo - $6.00 - x1
Sheet metal - Fasteners - Double sided tape - Velcro - Wire - Plastic - Battery Charger
The Total cost will be around $200 to build your first robot, budget accordingly.
Step 2: Design Basics
To keep things simple I'll follow the flow of electricity as it travels through the bot. Starting with the blue battery in the upper right the power travels through the yellow electrical disconnect. The disconnect is helpful for easily removing power from the system and also for charging the battery. After the electric disconnect the power is split to each of the electric speed controllers (square pieces with the extruded aluminum fins on top). The ESC that I choose are wired for a power switch so both speed controllers are wired to the simple on/off toggle switch. The Receiver, in the lower left, meters the power to the speed controllers based on the signal from the transmitter. At full forward the receiver opens each speed controller so full power flows to each motor.
I decided to make my bot a bit more interesting so I added a servo powered lifting arm. The servo plugs right into the receivers and gets its power from that. If you wanted to go really easy you could use high speed servos as drive motors, but I have never tried that path.
Step 3: The Body
I didn't have access to any metal working equipment so I made the body of the bot from a simple piece of sheet metal that I picked up at Home Depot. Using tin snips and cut the shape and bent the edges over a piece of wood. To make it safer for my son I wrapped the sharp edges with electrical tape to prevent him from cutting himself. To keep the battery, ESCs and receiver in place a glued Velcro strips in place and the corresponding Velcro to each piece. I like Velcro for this because I am able to easily taking components out to work on them while still holding them in place while driving around.
I used a Dermal cutoff wheel to cut a rectangle in the front of the body to hold the power switch in place.
Step 4: Wheels!
Choosing the right wheels and motor are often what I put the most time into. I didn't want this bot to go flying across the kitchen floor and slam into my wall so I choose a geared down motor and soft grippy wheel. When buying the wheel make sure that the hub ID matches the shaft OD. If the hub is too big or too small it will just make things more difficult. If you have limited access to tools I would recommend getting a motor that has a prefabricated motor mount.
I used a piece of 1" thick nylon to fabricate my motor mounts. After drilling the main hole, that should be press fit for the motor or gearbox, I cut a slit in the side. By drilling a hole through the slit portion I can tighten the screw and pinch the gearbox in place. I only drilled one hole in the bottom to hold the mount to the body, two holes would have been better! The last picture is of my battle bot showing a similar motor mount made from a different material.
Step 5: Electrical Components
The Electric Speed Controller that I choose is very robust and easy to use. It is important to pick a controller with forward and reverse (so you can turn and get out of a tight spot). The Red controller is from www.robotpower.com. Called the Hydra it is a great priced 3 channel controller! Connecters might not seem very important but if your wires break loose, are impossible to solder or can be plugged in backwards then you are going to have big problems. For small projects I'm a big fan of the XT-30 connecter. It was easy to solder to and is strong for its tiny size.
Another often over looked component is the wire that connects everything. A high strand count will bend a lot easier and will able fit in tighter spots. Don't just pick a big wire and figure its good enough, for a few dollars you can get several feet of good wire and it will last for multiple projects.
Now to the batteries. For my robots that I will be competing with I have to balance weight and size with the amount of power it can hold. For this robot that didn't really matter very much so I put in a bigger battery so I wouldn't have to charge the battery very often. Lipo batteries just make sense in small robots like this, and with prices so low why not? Size the battery voltage to match what the motor and control can handle. Picking a 1 or 1.3 milli Amp hours is plenty of power for this application.
Step 6: Other Electonics
As an added feature I stuck a servo to the top of the robot cover that serves as a lifting arm. I simply choose a servo that I come with one of my other transmitters, but there are hundreds of servos that would work for this application. What you attached to the end of the arm is completely up to you. My son tries using it as a grabbing arm so a claw would have been a good option. I mounted the servo on top of a plastic block to allow it to rotate without hitting the cover.
I would recommend buying a 2.4 Ghz transmitter because it has great range, low interference and no need for channel crystals. I bought a 6 channel transmitter because it will allow more options in the future. A 3 or 4 channel radio will be more than enough for a basic robot.
Step 7: Extras
There are always extra parts that make things easier or are just handy. The programing cord above is helpful to change the default settings on the transmitter. You can assign different channels to the control sticks or switch between one and two stick driving. Maintaining your lipo batteries is always a good idea and having a battery balancer helps keep your batteries working smoothly. The bottom item is a simple voltage readout that tells the overall charge and the charge of each cell in the battery. This helps let you know how much power is left and if the cells are all at the same voltage.
Step 8: In Conclusion
With a few basic components and a bunch of imagination you can build anything from a killer battle ready robot to a educational kids bot. The great part about all the components that I used is that if my son grows out of a simple wedge bot I can reuse them to make whatever comes next, or let him design the next bot. Thank you for taking a look and I hope you learned something!