Today we try something completely new! Let’s build an electric bobbycar, with 4 motors attached to a bobbycar kids toy chassis, with integrated battery pack for small, short rides in the city!
We will reuse the Motors, Electronic PCBs and maybe also the battery of old (broken) hoverboards. That should make the electric bobbycar really cheap (~100€ in total)
There have already been similar projects in germany:
https://larsm.org/allrad-e-bobby-car/
https://figch.de/index.php?nav=bobbycar
So the first step is to get an STM32 and flash Niclas’ firmware hack. We will do heavy modifications of the firmware later to make it controllable with analog inputs. The first test will spin the wheel on its own without any input:
It turned out that old xbox 360 controller’s L and R trigger have the perfect shape to fit inside the bobbycar steering wheel. Let’s modify the firmware so that it allows control of the spinning direction with a forward and backward trigger:
Now to the chassis: We do not want to weaken its structure but still we need to be able to put in batteries, electronics and other things. A hole on the bottom seems to do the trick! But it should be as small as possible. The motos will be attached to an aluminum plate with holes drilled.
![](https://brunner.ninja/wp-content/uploads/2024/04/20190802_221537-768x1024.jpg)
![](https://brunner.ninja/wp-content/uploads/2024/04/20190802_221657-1024x768.jpg)
Now lets put all the electronics in the chassis and connect them up to the motors:
![](https://brunner.ninja/wp-content/uploads/2024/04/20190805_234152-768x1024.jpg)
The motors are spinning! I would call that a success.
![](https://brunner.ninja/wp-content/uploads/2024/04/20191215_225331-768x1024.jpg)
![](https://brunner.ninja/wp-content/uploads/2024/04/20191217_230639-768x1024.jpg)
The maximum distance it can drive with me ontop is around 10-20 km, and the maximum speed is around 20-25kmh, but we will lots of improvements there, especially with enabling field weaking.
Changing any parameter of the driving behaviour is a big pain as I have to completely disassemble the device, take out the battery, take out the 2 motor controller boards, connect them with STM32 and so on. Every time I disassemble it I scratch my hands during the battery takeout procedure as the battery seems to be a little bit bigger than the hole in the chassis…
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