Bad stepper motor ??? How do I determine?

[thuffner3]

I'm running a small carving machine(home built) using a 3 axis controller from http://www.stepper3.com/31.htm. Up until today the unit seemed to be operating just fine. With some loss in stepps. My motors are 6v/1.2amp unipolar types. I'm using a standard 12v supply with 1 ohm resistors on the power legs. I was just informed that the correct resistor to use should be a 3 ohm for this setup???

(12v psu)-(6vdc motor)
------------------------------ = 3 ohm resistor,
2 amp current


What I found after playing around a little today was, one of the motors had basically no toque.

Could I have burnt this motor? How much current would be to much?
Neil

[HuFlungDung]

Where does the resistance of the windings enter into your calculation. I'm a noob at this stuff, but is it correct that that the resistance of your windings would be 5 ohms? That would make a total of 8 ohms, then, which would allow only 1.5 amps to flow.

(Shrug)

Maybe Balsaman could answer this, he's a real smartie at this stuff, amongst others (no offense meant to others )

[balsaman]

Here is the steppercalc screen shot: It indicates you need 4.25 ohm resistors. 4 would probably be fine (1.23 amps at the motor). Your 1 amp resistors make the motors draw 1.85 amps each. That is plenty high. Were they getting very hot?

Eric

[balsaman]

If you were using one resistor per motor it should be 2 ohms.

Eric

[Mr.Ed]

Great avatar you have there Thuffner3,

I don't know if you are familiar with that character, but earlyer this year that albino Gorilla passed away in Barcelona, after illness.

Nah...You probably heard that allready somewhere else.

I thought you might wanna know if you were unaware of this.

Good luck with your project, yes i noticed that too

Ed'.

[thuffner3]

Originally posted by Mr.Ed Great avatar you have there Thuffner3, I don't know if you are familiar with that character, but earlyer this year that albino Gorilla passed away in Barcelona, after illness. Nah...You probably heard that allready somewhere else. I thought you might wanna know if you were unaware of this. Good luck with your project, yes i noticed that too Ed'.

Thank you Mr.Ed, I didn't know this.

[thuffner3]

Could I have burnt this motor, or is the over current cause the loss of torque? When the motor is stationary I can with very little effort, rotate it.

[balsaman]

could be cooked...did you try it on another axis?

Eric