750W BLDC which driver/controller for simplefoc?


I have a 750W Lathe, the controller which it came with acts quite slowly.
So I came across the simplefoc and though this might be an application for it.

could anyone suggest a driver which could be used with a simplefoc controller to run this motor?
Accurate positioning would be quite helpful, currently the chinese driver doesn’t support it of course.


@MRx What’s the voltage that the motor runs on?

The motor is supposed to be rated 310~330V (according to the lathe manufacturer).
Can a BLDC be measured like that using eg. U/V and setting the multimeter to AC? then the maximum that can be set would be 192V.
The entire board is coated with epoxy so I’d have to get a new one I cannot modify that one.

By the way what I have here are some as5048a encoder and STM32F433 Nucleo boards which I use for prototyping, are those parts suitable for a simplefoc controller?

Two other people and me are currently working on high voltage(mains 240v) capable board’s, but I would advise against it if you are not 100% Shure what you are doing. Because off the dangers involved with high voltage.

Is the motor a bldc or asynchronous motor? A bldc has cogging when you turn it by hand, an asynchronous motor turns smooth when you turn it by hand.

I agree with @Franz_Schmidt. At least my board is at a development stage and might take a month or two to bring to a pre-release level. Even then my board will deal with DC currents only and won’t have the AC-DC rectifier required for your lathe motor, which I guess is right now embedded into the lathe power electronics, hence the epoxy you see, that’s to prevent tampering with the board, and I assume you plug it straight into the outlet.

Even when ready my board will cost at least a $100 to manufacture, and you need to manufacture it yourself, because what I will publish is just the schematics. I won’t sell it due to obvious liabilities.

May I respectfully advise you not to look into controlling your lathe with an unproven custom development board? I work in the industry and have seen enough DIY accidents to conclude my eyes and hands are not worth the money I would pay for hardware that does everything at a higher cost.

@MRx if you have a normal asynchronous motor than the easiest solution would be a vfd from eBay. There you have 2 cost effective options:

  1. Used industrial or surplus equipment, it’s mostly good quality and still in good working condition. I would go for a 1kw size. (I have a 0.75kw one from Emerson Wich was quite easy to set up and it was only 60€ brand new in box)

  2. A cheap Chinese vfd, there i would go with a 1.5kw one, just to have a bit more reassurance that it won’t blow up under load.

But I don’t really know if it is possible to use a standard vfd with bldc motors. Maybe there are special ones, but I haven’t come across one yet.
Maybe @Valentine knows more about that.

Your concerns are absolutely right however I’m still interested it in general.
I received a second board from the manufacturer which is currently not working (the manufacturer is supportive, but they also buy the boards from external).
There’s just light coating on the new board, the new board is equipped with an STM32F0 microcontroller (the old one is completely coated with black epoxy I don’t know which components are used).

That’s the first controller, there is no torque issue just a slow response of the controller. After adding load the motor slowly speeds up and overshoots once the load is removed.
This happens at every speed level and not only at low speed. Eg at 500 RPM it’s +/- 100 RPM. I converted the machine to CNC which works very well but the NC program has to match all those parameters.

To be honest the operation you are describing seams normal to me, in the past i have worked with one of the Chinese benchtop mills wich also had noticable overshoot. But I don’t know how it’s really supposed to be.

Does the stock lathe controller have a encoder/sensor connection so the controller knows how fast the motor is actually turning? Or is it done via current sensing. Maybe a picture off the new controller would be helpful.

No that is not a normal operation, because you set up the surface speed during CNC turning, on the outer radius the motor drives slower and quicker on the inside.
It gives a totally unreliable surface speed.
I have interfaced the potentiometer, and it sets the correct speed if there’s no load.

There’s a magnetic sensor inside the spindle which shows up the approximate RPM value (it has some timer and doesn’t change the value so often, I have also interfaced that one for measuring the real RPM value). That one of course is only for the user not for the controller.

There are 3 power wires, and 5 wires for the hall effect sensors. I can upload a photo tomorrow.

There’s a video of the new controller, does anyone know an electronic switch which might be suitable for switching the BLDC wires so I can control the direction via software?

Maybe you can train a monkey to flip the switch :rofl:

Sorry, no disrespekt to monkey trainers or trainee monkeys. I was just, you know… anyways. So you need a electric switch IC? Why not use a regular binary switch? On = forward Off= backwards… Wait a sec. is this a trick question!? Why would you want a switch to control the direction through software?

Controlled tapping.

Anyway there’s still quite some work to do, I need to check the wiring of the new board then the motor should just work with it.
The old board also started with 60RPM, the new board allows to start at 0RPM (so I can turn the spindle off after a job).