An Electric Unicycle, In Minimalist Form

When self balancing scooters hit the market a few years ago they brought alongside them a range of machines, from the hoverboard kids toys which have provided so many useful parts, to the stand-astride electric unicycles. These last machines have a bulky battery and controller box atop the wheel, and [Dycus] set his sights on this by transferring it to a backpack with the vehicle’s IMU sensor relocated to one of the pedals.

Such a job is not merely a simple case of rewiring with some longer cables, as a first challenge the IMU communicates via I2C which isn’t suitable for longer distances. This is solved by a chipset which places the I2C on a differential pair, but even then it’s not quite a case of stepping on and zipping about. The PID parameters of the balancing algorithm on a stock machine are tuned for the extra weight of the battery on top, and these needed to be modified. Fortunately there have been enough people hacking the STM microcontroller and firmware involved for this task to be achievable, but we’d rate it as still something not for the faint-hearted.

The final result can be seen in the video below, and the quality of the physical work shows as very high. The former battery box is repurposed into a stylish backpack, and though the newly minimalist foot pedals and wheel are a little less easy to get going he zips around with ease.

Hungry for more? This ain’t the first we’ve shown you.

18 thoughts on “An Electric Unicycle, In Minimalist Form

      1. This is for clout within the EUC community, not YouTube likes. :) Really its main purpose was a fun engineering challenge, with the side benefit of having a unique parking lot wheel before group rides start. It’s obviously less practical and more dangerous than a normal EUC (which are fairly easy to jump off of if necessary).

        I do wear a full-face helmet on these, I just had the skate helmet on because I was doing tuning and testing and wanted something easy to don and doff.

        1. @Dycus said: “I do wear a full-face helmet on these, I just had the skate helmet on because I was doing tuning and testing and wanted something easy to don and doff.”

          Speaking from experience, “tuning and testing” is the #1 domain for epic face-plants. Be careful. Set a good example for the Cheeeldren!

  1. The package is tidy. Good use of 3d printing – I especially like the steel cable with clamps. Needs 1 more feature: a hook on the backpack to hold the wheel

    Poisonally I’m scared of these forward-facing standing vehicles.

    1. when running, at what speed do you alter your gait to TURBOCRAB?
      When you ride a bicycle at what speed do you go side sadle?
      When you were a kid did it make you sad that you couldnt roller skate?

      1. Let me rephrase my complaints
        1) you have to face forward and shift your bodyweight forward. Asking for a tumble
        2) it’s a mono wheel, you have to balance in all directions, including pivoting
        3) there’s stuff in between your feet complicating a bail

        I’d rather bomb a hill in heelys

        The only upside to this vehicle is that the wheel is over a foot in diam so it can run over pebbles. A bigger wheel like a bike or regular unicycle is better. The seated kind seem safer (but they’re also design to go faster to whatever).

        1. Here i can provide some assistance as I do ride those “crazy unicycles” — saw this post while packing up for a 50+ mile ride today.

          1) not wrong, but side standing like a “oneWheel” (TM) is actually worse (we can run off forward consuming a fair bit of intertia on each impact, they can’t crab walk off fast enough making collar bone breaks their #1 serious injury).

          2) Yup, that’s kind of the point ;-) . Centrifugal force is pretty significant at higher speeds, but it definitely is a “conversation” between your feet, hips, and shoulders with a single point of contact to the planet.

          3) More or less everyone, when they start to fall, will instinctively “run off” the wheel (forward). Much of the time we are traveling faster than we can run and so we will get 2-4 foot strikes and then our legs get kicked behind us. If your luck, quads, and focus are good you then drop to your extremely heavy duty knee + shin guards, lean back, and slide it out.

          One last note: there aren’t standing vs sitting EUC’s. Pretty much every seat is a mod (optional part from the factory or aftermarket) and it is generally understood to be an extra skill/trick to learn to ride seated as it is a fair bit trickier than standing. Probably for the best, a lot slower response to trouble from a seated position.

          All that to say: yeah EUC’s certainly do present a challenge and a safety risk to the rider, but it is an entirely unique feeling of movement due to the single point of contact (almost feels like you are fixed and the world is moving) and with a bit of practice the risks go down.

          Last but not least: all the safety gear, all the time: DOT rated motorcycle helmet, class 5.5 wrist braces (hard front and back of wrist support), thigh+knee+shin hard guards, elbows, and Kevlar sneakers.

        2. I’m a little interested in the sort of electric-heely adapter for regular shoes I saw somewhere. But probably I’d rather a very compact electrified version of the old razor scooters we had as kids, only taller of course. The tubes can hold cylinder cells. Otherwise, just an ebike I guess, for the wheel size.

  2. Extending I2C is worse than any other single-ended bus. Just use a cheap micro and convert it to RS-485/422/CAN or similar with a basic protocol. Placing all the controllers in one end screams trouble.

    1. Did you read the second paragraph in the article? Or look at the schematic (second picture) in the linked forum post?

      The I2C has been converted to differential using a chip made for exactly this purpose. Physically, it’s a bit similar to CAN. There’s only about 1 inch of actual single-ended I2C at the controller end and even less at the wheel end.

  3. Quick question, has anyone complained about the motorized unicycles being too big / bulky between the legs? Or is this just a “if your a hammer then everything looks like a nail” situation?

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.