[kloporay]

Hello everybody,

I've managed to salvage an old Nema34 Minebea unipolar stepper motor (6 wires), which has the following characteristics: 14V/phase, 0.7A/phase.
I'm planning to do a project with an Arduino board (not exactly a CNC machine, but I do need precision in driving a lead screw), and I was wondering what kind of a driver I should get, provided that I want to minimize costs on the one hand, but I do want it to perform on the other.
If I understand correctly:
1. 6-wire unipolar motors can be hooked up to operate as bipolar motors, either in full-coil (leave the center tap hanging at each phase) or half-coil (connect to one of the phase wires and the center tap at each phase) mode.
2. Due to the above, I could get away with relatively cheap, mainstream (bipolar) drivers, like even the Easy Driver (750mA max), or the TB6600.
3. The low current rating of 700mA means that it has high inductance, i.e. it will not run very fast.
4. Connecting it in half-coil mode would retain the same characteristics as unipolar operation mode, but full-coil connection would result in more torque, but also 4 times the inductance, making it even slower (yet more powerful).

I was wondering first whether this is correct, but also:
a. What current should I supply to the full-coil bipolar connection of the motor? Is it still the same 700mA?
b. Which driver would you recommend for me to get?

Thanks in advance.

[awerby]

It's hard to say whether this will work for you, since you don't say what you're trying to do. But the first thing would be to find out more about that motor you want to use. I tried looking it up in this chart of older Minebea steppers:

Minebea Stepper Motor Specifications

but couldn't find one rated at 14v. The nameplate voltage rating on steppers doesn't really mean much anyway; you'd typically feed them a whole lot more. You mention that it has high induction; that means it will take a lot of voltage to run it effectively, which could rule out the cheap drives you want to use, since they typically won't tolerate much voltage. If the main object is to use those drives with an Arduino, figure out how much voltage they'll handle, and shop for a motor that won't demand more than that, using the equation 32 * (square root of) induction = optimal max supply voltage.

[James Newton]

These pages may help:

Different connection options:
techref.massmind.org/techref/io/stepper/connections.htm

How to work out which wire is which:
techref.massmind.org/techref/io/stepper/wires.htm

Easy Driver isn't bad. I don't recommend the TB6600... they are... twitchy. Also some of the larger Pololu drivers will probably manage that motor. And of course, my drivers would be best... ,o)