Newbie with feasibility question


I have stumbled upon simpleFOC and looks like the answer to my prayers! I am building something and am quite good on the mechanical and fabrication side but I am a bit too much ‘work with my hands’ for my own good. When it comes to code and electronics I become a little stuck and don’t have as much understanding as I would like.

I am trying to learn though and have been lurking for a while. I am hoping that if I state what I am trying to achieve someone may be able to point me in the right direction.

I am trying to run a lead screw at around 4rpm using a gimbal motor as a direct drive, with some adjustment on a potentiometer to go a couple rpm or so +/- . On a momentary switch I would like the motor to be able to run at a much higher rpm for a few seconds, as and when required.

I have managed to do this using two DC gear motors, (one low rpm and the other high rpm) with pulleys on sprag bearings and belts. This works but is noisy and requires making belts, pulleys, etc.

I like the idea of direct drive from the motor to reduce the amount of parts and more importantly, using a brushless gimbal motor, I am hoping it will be near silent. Silent and smooth are highly desirable to me in this scenario. Also the small flat size of a gimbal motor makes the fit ideal too.

I have bought a gimbal motor with 11KV and have a couple others on the way, which are around 25kv and 75kv.

I am hoping FOC will allow me to run one of these motors at 5rpm (from what I gather they can) and also at a much higher rpm on a momentary switch.

I have tried running the motor with an ESC but it’s noisy, torque is low and movement is a bit jerky. It’s also running too fast at around 20rpm minimum. Hence looking at FOC as I suspect it will sort these problems.

Please could I ask, what would be the most suitable solution for this, I presume the SimpleFOCMini mini with a particular driver? I would like to be able to control the motor with a potentiometer for the speed at around 5rpm, use a manual switch to turn it on and off and a momentary switch for the brief higher speeds from the same motor.

I only need the motor to run one way as the carriage on the lead screw will manually be lifted back to the start. I will be pressing start and it will slowly move in one direction until it gets to the end. Will I need a positioning encoder for this?

I need to make a bunch of these so a simple solution is what i’m hoping for.

Many thanks


Hay! Interesting projects. Sound like it is part of a production-line ?

Regarding your question. It all depends. Friction (inertia), heat, so on and so forth. Seams like you intent to experiment with various motors. I think that’s a good approach.

My suggestion is to measure the motor temperature, when in use for extended time. If it is part of a production-line, then it most likely should run for hours.

I’m thinking spring loaded end-stop (sensor) like when train-wagons connect.

Sounds like you should be able to use open loop velocity mode (no encoder). And the program to read the potentiometer, button, and limit switch should be very simple (analogRead for the pot, digitalRead for the others, then set motor velocity accordingly)

What is the diameter and lead of the screw, and how much force do you need? That will determine the motor size/power needed. Then the kv determines the proportion of voltage and current the driver will need to supply.

Hi thanks for your reply.

It’s an engraving machine I am making essentially. It will only need one lead screw per machine, although I would like to make a few and perhaps sell some, as I have had some interest from people already and it’s not even finished yet. Hence needing to make a small batch. I also like to approach anything I build with the idea of making multiples and repetition in mind, even if just for the challenge and consistent quality.

Hi thanks for your response.

Good to know I could use this open loop.

The lead screw diameter is 8mm. Ideally it needs a good amount of torque as I like to over engineer and I want to minimise vibration, so mass in the carriage wouldn’t be a bad thing. Weight of the carriage moved by the lead screw would be around 300-500grams approx. Could be made to weigh less though, or more if I can get a way with it.