I've decided to make a stand alone thread for this...
Youtube video with instructions:
https://www.youtube.com/watch?v=0xb_N9yZejc&t=37s
I have been working on my own design for a gauss meter for spec racing rotors. I say spec because it can only measure up to about 1850 gauss. Well, I can make one that will measure up to 4000, but it is a bit more sensitive around zero.
This is based on the ATmega 328p mcu that the Arduino Uno uses. I also am using an external 12 bit adc to get better resolution for the readings, since the arduino has a 10 bit adc. I designed the schematic and the pcb using KiCad, the case is 3d printed and designed in Fusion 360. I am using an arduino sketch for the programming. In theory, someone handy in soldering surface mount components could build one of these based of my designs, which is completely fine.
It works pretty much like the other units on the market. Place the rotor on the holder and spin it to get your readings. I am using 3 sensors to get readings, the middle sensor is the sensor that you should record. The first and the third sensor are there for you to center the rotor. Shim the end of the rotor until you get the 1st sensor and 3rd sensor close in readings at the max value, this will get the middle sensor in the middle of the rotor.
The Rotor Master can be powered off a 2s or 3s lipo or 12v DC power supply. It comes with an XT60 connector on it as a hardware reverse polarity protection. There is no internal circuitry for reverse polarity protection. I probably will add this in the future. Each unit is assembled by hand (mine, lol). I use an accurate bench top dmm to measure each sensor to get the most accurate build that I can. I then calibrate it to a Trinity certified rotor readings.
For anyone who wants to make one themselves, I will provide the schematics, pcb designs, bom, stl, and sketch files needed to make one. I'll get them all into a github repository if there is any interest in it. But making one yourself will require an accurate dmm, an arduino Uno to burn the bootloader on to the bare 328p mcu and then to program it via the rx/tx pins that are broke out.
github repo:
https://github.com/trilerian/Rotor-Master
Anyway, here are some pics of the schematic, and pcb design. And then the progress of designing. Enjoy!
Schematic
PCB
Proof of concept
Top view of POF
I ordered 20 PCBs!
Getting ready to build!
All the smb stuff soldered on.
And then the through hole components
The finished product!