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2 layers24 × 32 mmMt6835-hoverboard, the printed circuit board in 3D

MT6835 magnetic Encoder Breakout board, eg. for mounting inside Hoverboard motors

Size
24 × 32 mm
Copper layers
2
Thickness
1.6 mm
Parts
14
Nets
14
Pads
82
Tracks, vias
186, 7
Pours
33
Routed
Yes
KiCad
KiCad 8.0 (file 20240108)
Created
1 Jul 2024
Updated
29 Jan 2025

Overview

Mt6835-hoverboard is an open-source printed circuit board by mcells, from the mcells/mt6835-hoverboard-motor repository on GitHub. It is a 2-layer board of 24 × 32 mm with 14 parts on 14 nets, routed with 186 tracks and 7 vias.

It is built around the MT6835 and BDFN2A051U. Its parts include 3 connectors, 2 capacitors, 1 IC and 1 diode. It belongs with the robots and motor control boards of this library.

Main components

2

README

README.md

mt6835-hoverboard-motor

MT6835 Breakout board, eg. for mounting inside Hoverboard motors

FrontBack
Top sideTop side

Features

  • MT6835 Encoder
  • 25x25mm diagonal M3 mounting holes that are removable by breakaway sections
  • 14.2mm diameter, making it small enough to fit onto the 15mm shaft of Hoverboard motors
  • M2 mounting holes, 10.6mm apart to facilitate mounting.
    • Nonconductive screws or spacers are necessary to prevent shorts!
    • Designed to be screwed into corresponding M2 holes drilled and tapped into the shaft, the cabling will go through the drilled-out center of the shaft.
    • A similar approach is described here
  • Breakaway drill template
    • drill out the motor shaft to 5mm and use the drill bit to locate the template on-center, then mark and drill the M2 holes
  • All usable Pins broken out to three sensible 6-pin headers
    • SPI interface on 1.27mm header, with enough space to mount a 6-pin 1.25mm Molex Picoblade
    • UVW and ABZ (together with CAL and PWM pins) on 1mm Pitch headers (due to space constraints)
  • TVS diode footprint can accept the one from the breakout board commonly available on Aliexpress
  • Sleek design

Renders

FrontBack
Top sideBottom side

Installation inside a Hoverboard motor

Installing the sensor board inside a Hoverboard motor requires you to have access to the following tools:

  • A Hoverboard motor and
  • A sensor board (obviously...)
  • A drill press (though using a hand drill might work, if you are careful)
  • 5mm HSS drill
  • 2mm HSS drill for marking the locating holes
  • 1,6mm or 1,7mm HSS drill for the M2 threads
  • M2 tap
  • two M2 screws for mounting the sensor
  • soldering stuff
  • a saw or dremel to cut out the round part of the PCB

Steps

StepImageDescription
1Disassemble the Motor, until you have just the bare Stator. Desolder and pull out all wires, so you can drill through the shaft.
2Step 2Drill a 5mm Hole inside the top of the stator shaft. There is a centered "dimple" already in the shaft, which helps with centering the drill enormously. You want everything to be as concentric as possible, else you will get a periodic nonlinearity in the measured angle! You have to drill about 25mm until you break through to the hollow shaft.
3Step 3Remove the drill bit from the drill and put it most of the way through the new hole, so that just protrudes at the top. Use the drill bit to locate the template PCB on the center of the shaft.
4Step 4Either use a center punch, or, using a M2 drill bit, pre drill two "dimples", so you can later locate with the smaller drill bit. When drilling the second dimple, use something like a small allen wrench in the first dimple to hold the template in place.
5Step 5Drill the two holes with a 1.6mm or 1.7mm bit and tap the holes to M2. You can use a 1.7mm drill to ease the tapping, as the threads don´t need to support any significant load. Also refrain from tapping more than a few mm deep, as it is absolutely not neccesary and just increases the risk of your tap snapping off.
6Step 6You can now mount the sensor. Take care to use either 3d printed isolators like I did, or use plastic washers. Else you will short the sensor out! I had to drill out the 5mm hole to 6mm to make my sensor wires fit. If you have thinner wires, 5mm might be enough for you. I replaced the original wiring with new one.
7 (optional)Step 7In these motors, the 3 phases are each wound using multiple strands of enamelled copper wire, some 3, 4, or even 5 in parallel. The phases are then connected in a star, or Y topology. I wanted to lower the kV as much as possible, so I unsoldered the strands and connected them in series for each of the three phases. This lowers the kV by the number of strands you serialize, in my case three.
8Step 8My motors have just enough space inside, so that the magnet can be mounted directly inside the rotor bell. I marked the center of the bell by pushing a 15mm HSS drill into the bearing (15mm inside diameter) and turning the bell. This leaves a perfectly centered dimple exactly where you want to mount the magnet. The aluminium there is about 2-3mm thick. Drilling about 1mm with a drill bit of the same diameter as your magnet lets you just glue the magnet there, without drilling from the outside.

Where to get the boards

I got my PCBs fabbed and assembled at JLC. You can use the provided KiCad project files to generate the required files. You don´t have to get assembled boards directly, as I designed the PCBs so that you can desolder the components from the aliexpress board and solder them onto this PCB. This might be far cheaper for single quantities.

If you have any questions, feel free to just create an issue/discussion or ask me on Discord (@hollowedbethyname)

Parts

14
QtyValueFootprintReferences
20.1µFCapacitor_SMD:C_0402_1005MetricC1, C2
2PinHeader_1x06_P1.00mm_VerticalConnector_PinHeader_1.00mm:PinHeader_1x06_P1.00mm_VerticalJ2, J3
1BDFN2A051UDiode_SMD:D_SOD-882DD1
1MT6835Package_SO:TSSOP-16_4.4x5mm_P0.65mmU1
1PinHeader_1x06_P1.27mm_VerticalConnector_PinHeader_1.27mm:PinHeader_1x06_P1.27mm_VerticalJ1

The 7 most common of 14 parts.

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Questions

How big is the Mt6835-hoverboard PCB?

It measures 24 × 32 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Mt6835-hoverboard use?

14 parts, built around the MT6835 and BDFN2A051U. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Mt6835-hoverboard KiCad files?

From the mcells/mt6835-hoverboard-motor repository on GitHub, at the commit this page was made from: the board is mt6835-hoverboard.kicad_pcb and its schematic mt6835-hoverboard.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Mt6835-hoverboard design in my own project?

Its repository states no licence, so its author keeps all rights: ask mcells before reusing the design.