Picture of Self Balancing Unicycle
Following the popularity of our self balancing scooter and the SciChair we decided to try something a little edgier, the Self Balancing Unicycle.

This project reuses a lot of stuff from our previous projects, using an arduino as the brains behind the scenes.

Step 1: Ready your tools

Picture of Ready your tools
Before we begin lets ensure we have everything we need. For this project you probably want to be fairly comfortable with welding as you need to build a rigid frame.

Additionally you will need:

•Steel square tubing for frame
•24VDC 300W motor
•Arduino UNO - Check your local suppliers or eBay.
•Sabertooth 2x25 Motor Controller ( www.dimensionengineering.com or a local supplier)
•5 DoF analogue IMU - available on ebay (to be replaced with digital IMU at some point)
•Scooter wheel, sprocket, chain and axle - available as a kit
•Shielded multi core cable for the accelerometer and heavy power cable for the motors
•Deadman switch
•Toggle switch for adjusting balance position.
•DC connector for Arduino.
•DIL pins to suit Arduino
•Double sides tape
•Screws etc
•Drill and drill bits
•Welding equipment and saftey gear
•Soldering iron and solder
•Wire cutter and wire strippers
•Heat shrink and hot air gun to shrink it

Step 2: Frame and motor

Picture of Frame and motor
The seat is sourced from a second hand unicycle as we are lucky enough to work in an office where you can rely on someone having a unicycle they don't ride much anymore. The shape of the seat is important as you need to be able to shift your centre of gravity forward and backward on the seat, something more difficult on a regular bicycle seat. We attached it to the frame with a simple steel pipe, nut and star hand knob tightening screw.

The wheel, sprocket, chain, and axle all came in a kit designed for a scooter.

We used 25x50mm tubing for the frame and 25mm for the foot pegs. A couple of plates across the middle of the frame served to mount the single motor with a piece of acrylic to which we glued or screwed the electronics.

The axle was set in a channel which allows the two sprockets of the motor and wheel to be moved so the chain can be easily fitted.  A bolt above the axle stops it from suddenly sliding upwards when in use.

Step 3: Connect arduino to Switches

Picture of Connect arduino to Switches

We built this model with an ardunio nano but are in the process of transitioning to an arduino uno to keep our projects on a standard platform. The code and pin-outs provided here are for an arduino uno.

To connect the Arduino to the 3 position rocker switch to adjust trim and the push button kill switch:

Arduino - Switch
GND   -> 3Pos cen, push button -ve
D9      -> Push button +ve
D10    -> 3Pos 1
D11    -> 3pos 3

Step 4: Arduino to ESC

Picture of Arduino to ESC
Now to hook the motor speed controller up to the serial interface on the electronic speed controller (ESC).

Arduino   ESC
GND -> 0V connect this to the same rail that you were using for the sensor
5V     -> 5V
D13   -> S1

This would also be a good time to set the DIP switches on the Sabertooth to the right settings for serial control.
1 - On
2 - Off
3 - On
4 - Off
5 - On
6 - On

Step 5: Arduino to IMU

Picture of Arduino to IMU
Next we will connect the Arduino to the IMU (Inertial Measurement Unit). As we're still waiting on the libraries for the new digital IMUs this project was created using the now harder to obtain analouge IMU, previously sold by sparkfun, now available on ebay (link).

A0    -> Y4.5
A1    -> Z Acc
A2    -> Y-Rate
A3    -> X-Rate
3.3V -> 3.3V

Step 6: ESC to Batteries

Picture of ESC to Batteries
Finally it's time to connect your ESC to the battery packs, motor and master switch.

B+    -> Pos battery terminal - optional - In & VCC on voltmeter
B-     -> Neg battery terminal - optional - GND on voltmeter
M2A -> 24VDC on motor
M2B -> Motor GND

If you have wired two 12v batteries in series you can place the master switch in the middle.

Step 7: Code

Picture of Code
This is the same code used for the self balancing scooter with the steering sections commented out, again credit goes to XenonJohn.

I have added the code but you need to change .txt extension to .ino

A final note on testing

This vehicle requires a little more skill on the part of the rider than the Scooter or SciChair, it also requires a little leap of faith on take off. This faith should not be easily given however, one silly mistake, like wiring the motor backwards (cough) will result in this machine throwing you face first into the dirt. As such I strongly recommend laying the unicycle down on the ground, switching it on then lifting the seat up with both hands ready to lift it off the ground if it decides to fully engage the motor. Once you're happy that it is properly sensing its tilt lower the wheel onto the ground and slowly lean on it to test its responsiveness. Only after all this should you attempt to climb aboard and even then, a helmet is strongly recommended.

Good luck!

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67tadejudrih6 months ago


can i get electrical schematics? because I can not tie electrical work


soliveira97 months ago

Nice project!

But I think there is one thing left... Can you put photos showing all the connections? I think that is what all people want to see!

SidharthG7 months ago

does the rpm of the motor matters?

i mean do we need the rpm to be in a certain range, or it will work for any range of rpm

mdrafeeq.khan8 months ago

can i use BTS 7960 b instead of sebertooth controller

Fun project! well done.

what is the weight of the SBU?

I bought a moCycl at and they say it is the lightest SBU.

PranavN8 months ago
please.. can you make the battery specs available. ?
PärM19 months ago

Great for all of those skillful techies out there who likes the idea of a self build. For us with laziness as a way of life, just head over to moCycl.com and order a ready made one delivered to your doorstep. cheerio

XenonJohn PärM19 months ago

This Russian one is best properly controllable design I have seen with steering and a seat. Does not come up on any search engines but check out the video. Quite low priced too.


pierretotz110 months ago

Im planning to build one, is it possible to build it with an inhub dc motor typically found in ebikes?

Hub motors these days are almost all brushless. This means you need a brushless motor power controller that can be controlled by your arduino. It can be done but expensive.

guys is there any book that has orderd programming tutorials on arduino

PranavN10 months ago

Cool project. Liked it a lot. I am thinking of trying it, but I am experiencing a problem choosing correct battery. Could you please suggest the right one, like if you tell the one you have used, it will be excellent and helpful.

Thank you.

ZackY111 months ago

Do you guys like self balancing unicycle without a chair?

fwenzel1 year ago
Where is the code??
ScitechWA (author)  fwenzel1 year ago

Step 7 - Code.
Open the txt file and copy the contents into the Arduino IDE or rename the file extension to .ino

They will not allow a file with .ino on Instructables.

Thanks for the fast answerse, but, in step 7, here in my PC, I could not, found file for download. I think something is wrong here... Please, can someone send me for email the code. frediwenzel@gmail.com
ScitechWA (author)  fwenzel1 year ago


BikeHacker1 year ago


JimRD1 year ago
Where is the code?
ScitechWA (author)  JimRD1 year ago
Sorry, but i could not found it...
danaG751 year ago

I have a quick question concerning the toggle switch for balance position.

Are you using a SPDT Rocker Switch and is it monetary?

I also plan on build a unicycle very similar to yours and I'm currently the sourcing parts.

Tyde1 year ago

Super unicycle
I'm also building
I would like to have the dimensions of the frame
to the same

Thank you in advance
congratulations on your new tutorial, and thanks for the valuable advice you give.
MaleBuffy2 years ago
What size wheel is that and what size sprocket?
ScitechWA (author)  MaleBuffy2 years ago
It is a 12.5" wheel with a 80 tooth sprocket from http://www.oatleyelectronics.com/
Under wheels.
catoctober2 years ago
Where did you get the wheel, sprocket, chain, and axle kit?
ScitechWA (author)  catoctober2 years ago
They were bought from http://www.oatleyelectronics.com/
jgabuna2 years ago
Awesome project. Looking forward to see a 3 axis self balancing steadicam. :)
Dylon1242 years ago
How much did the arduino cost?
ScitechWA (author)  Dylon1242 years ago
The arduino uno is about $33 AUD on Sparkfun but you can find them for around $12 on ebay.
PLEASE use a standalone arduino!
Crotus2k2 years ago
Of all the cool gadgets I saw on TV, cartoons and in comics growing up, I would not have guessed that B.C.'s ride would ever be made into reality. You guys are great. Keep building stuff just because.
ced782 years ago

Great, I'd like more details on the construction of the frame Self Unicycle
ribs, material, etc.
Looks cool, but... video?
ScitechWA (author)  fungus amungus2 years ago
A gross oversight. Video is up now.
bob30302 years ago
Cool. I like arduino and Mobility devices. Great way to make a unicycle that Segwayed into a robotic mobility device. (sorry for the humor attempt). Thanks for posting.
wilgubeast2 years ago
Cool project, and that final note on testing is fantastic.
jxross2 years ago
Everyone is thinking it so I'm gonna' just say it:

The first photo just looks "wrong".

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