Question Alternatives to the standard MIGe servo for FFB

Hello guys,

I'm starting to work on my DIY project but I'm on doubt regarding the servo to use for FFB. Searching around here I've found most people commenting on the MIGe's and it seems is the sure way to go for FFB action. My problem is: I don't live in the US and haven't found any seller here (Brazil) which supplies servos from this brand. Not just that, but finding a way to import a MIGe would be extremely out of question due to shipping costs, import taxes and the USD -> BRL conversion itself, even though there's still a way of doing so.

I haven't worked with servos ever, but I do know a thing or two about Arduino, Rasp Pi (i'm planning to use one of these) and signal processing in general. Working with PWM shouldn't be a problem in the near future, for instance. Anyways, I'm not familiar with the restriction of servos and their actual difference from standard electric motors (is there any?). However, what I realized is that one of the main applications of MIGe motors is for MIG weld machines (ikr, thats some big thought process right there) - and replacement motors for mig machines are pretty much something I can easily find around my place, though not as much powerful (1kW) as the MIGes.

At last, I wonder: can I use any MIG machine replacement motor with a reasonable power capacity for FFB successfully? These are some easy to find around here, I guess it's pretty easy to understand the Balmer's label though it is in portuguese. Bahlmer's power is rated at 45W, and WireFeeder's rated at 120W.



These seem to have the same wiring of the logitech wheels ffb motors. I suppose you can control them with PWM and, if that's possible, I can easily take it from there. Can I use these for FFB?

nice motor, where did you bought it?

fer

Worm gearbox wont work for FFB. You need direct drive, or planetary with low rate division, to be able to backdrive the motor by hand!!!

See a small one that I made, to understand what I mean:
https://www.thingiverse.com/thing:3012316

These are MIG weld machine motors that can be found in the "brazilian ebay", www.mercadolivre.com.br

Don't expect sellers with any knowledge on how to export anything from Brazil though.

Thanks for the reply. Hmm, I'm not sure I understand the difference between these (worm, direct drive and planetary) from the project you sent. Could you elaborate a bit?

Worm gearbox: usually cannot back driven.

Planetary gearbox: can back driven in lower ratio. Amplifies the Newton torque the motor can provide.

Direct drive: the motor itself provides the torque directly. Works best on real servomotors where torque can be locally calculated based on its optical encoder feedback. Does not work well on plain DC motor, unless you have a way to deal with the high currents generated during stall of the motor (close to short circuit).