# Stepper motor

Hi, just a basic question, but I have a stepper here with four wires coming out of it one of which is gnd,

Is it a three or four wire Stepper motor?

I am slightly confused so any anwser would be appreciated,

Cheers

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Identify each color of the wires... that is a key for most of these problem. Now you should have a black one... this black one should be ground. If it is not black... look for the darkest colored wire... it should be ground. To test, take your multimeter to it... and find something with a positive power. Example... but the black lead of you multimeter to your dark stepper motors wire. Then put you red lead of the multimeter to the positive side of any fresh battery. If you multimeter reads the voltage that battery should be at... that wire is it. Most companys coat their wires that are ground black or a dark color. Hope this helps!

is a bipolar stepper. Bipolar steppers do not have grounds, as such. What you have is access to the two coils that drive the stepper motor, and they are the pair of the coils that will require proper activation sequence.

First, you will need to find out which pairs are connected. Get your trusty multimeter out and see which two have continuity, are connected. Next, you should attempt to find out how much current they require. You know ohms law, right? V = I*R You only need two out of three of those variables and you can calculate the third. I = V/R or R = V/I Now, you can get a motor driver that can handle the current draw of your stepper. After that, it is just a matter of energizing the proper pairs in the proper order to get your motor to 'step'.

Could'vd known that before...  learned that... Screw learned that, and I hope mine still helped. But that is something very important to know.

someone with more knowledge of steppers will correct me if I have mis stated something.

I agree with Birdmun, its probably bipoloar.   the 2 pairs are connected to the 2 windings inside the motor.   most likely, the 1st pair go together, and the last pair go together.   the easiest way I find to use these motors is to use a stepper motor driver. pololu offers 1 for around \$15 US.   it takes 2 wires from the MCU.  1 is for direction (high or low = clockwise or counter-clockwise) and the other is to send a step.   each time you drive that wire high, the motor will step 1 notch.   these motor drivers will figure out how to excite the 4 wires to do what you want.

do some research on the motor part # to find spec sheet.   some motors have the important rated specs printed on them, such as 3 ohms, 1.5 degrees (per step), and 3.5v.  you can give it more volts than that as long as you dont exceed max amps.  calculate the max amps using ohms law.  so in this case: I = 3.5v / 3 ohms = 1.166 max amps.   you would then use a resistor to limit the current to not exceed 1.1666 amps.   dont forget to add the motor's 3 ohms to the total resistance when calculating which resistor to use.    let me know if you need any clarification.