Bijgewerkt: 31 jul 2019
This is the first part in a blog series about a onewheel project I'm planning on doing. So I came across this board called the onewheel, that I absolutely wanted! But being the cheapskate that I am, I won’t buy one, I’ll make one of my own!
It can’t be that hard to build a DIY Onewheel!?
All we need is some electronics, a kart wheel, batteries & some building material.
The electronics would consist of two pressure sensors placed under one of the feet, a six-axis motion sensor to sense the orientation of the board, an ARM processor to do all the calculations, an ESC to control the motor, an optocoupler between the processor and ESC to completely separate the MCU from possible back-EMF and a bluetooth module to be able to do configuration in a phone app.
The batteries and the BMS would be rated for something like 50 Amps continuous, 48V.
The Battery Management System keeps all cells in the battery balanced and makes it possible to charge the batteries in-circuit, which means we don’t have to remove the batteries each time we want to charge them up. The batteries will be self assembled and stored in the board itself.
To provide the processor with power from the large battery, we'll need a BEC or buck converter circuit.
The kart wheel needs to be smooth, with rounded edges in order to make carving easier. The motor assembly including stator, magnets and housing will be created by myself and be placed inside the wheel. We also need to make sure we can inflate the wheel when the motor is inside.
The building material needs to be light and strong, so we could use aluminium or carbon fiber. We don’t want any flex in the board, since the batteries will be incorporated in the board, and doing good calculations for the boards velocity and orientation would be near impossible if there was any flex. Based on the above I'm thinking if it might be better to just buy an off the shelve flightcontroller for a quadcopter, they basically have everything I need and might be cheaper in a packagedeal like that.
Stay tuned for part II