DIY Speed sensor | Bafang BBSHD sensor reverse engineering

This is a complete repurposing of this thread. Short story, I've broken 8FUN speed sensors in the past and finding information on how this speed sensor works was impossible.
This thread aims to provide schematics, simple measurements, sample 3D designs and a place where people can talk about 8FUN and DIY speed sensors in general. :wink:

In the post below I posted a bunch of information about the 8FUN sensor and a collection of various ready to print 3D files, that I made.
This is the ready to print robust sensor body you will find in my collection, I just mounted it to my bike: https://imgur.com/D46fbDL https://imgur.com/zJj7IV8 https://imgur.com/6xg5bjM (The red stuff is silicone that I use to keep water out, PLA walls aren't water proof so you may want to protect the electronics by using silicone. And painting the plastic parts you've printed, I choose to give the print a coat of transparent primer, but I might paint it black in the future.)

You may be able to use a simple reed switch between signal and ground, or signal and power.

If not, a hall sensor like the Honeywell SS411A would probably work.

If you want the LED function to make it visible, just put the LED with a 5k or 10kohm resistor from the signal line to 5v; it should light (dimly) when the hall detects a pole change.

Wow, this post is now over a year old. I'm back to change this thread into something that could help people.

I got a new BBSHD speed sensor and the plastic snapped again! I decided to take it apart and see what makes it tick and if I can design something that isn't mounted with a plastic stick. The schematic you find here will work for all bafangs and many other controllers. I currently use it on my ASI controller.
Disassembling this sensor is not easy since everything is coated in a clear epoxy.


I'd say there's 3 parts to this sensor: the holder, a body+door and the electronics+connector

The holder:
Dimensions [mm]: (I don't know what dimensions would be relevant.)
The part: https://imgur.com/nIfkFu7 https://imgur.com/ufomwym

The body+set screw+door:
"Tube" dimensions [mm]: 25,2 x 12,2 x 12,2
Parts of it: https://imgur.com/kt2HlXz https://imgur.com/TMt3muT

The electronics+connector:
PCB dimensions [mm]: 6,3 x 14,7 x 1,6
Circuit: https://imgur.com/45VYEjW
Pinout(the sensor side, NOT the cable side): https://imgur.com/qgtQxeg
The part: https://imgur.com/VkBSqND https://imgur.com/SZXK9wv https://imgur.com/EgcCIVt


Parts for those who like to 3D-print: https://www.thingiverse.com/progamer_1337/collections/speed-sensor-stuff