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Stepper motor driver

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I bought a stepper motor with 6 wires. I wanted to drive in unipolar mode using 9v battery but it is not moving. Based on YouTube video I was trying. I don't know much about stepper motor. What voltage should I apply to drive it? Please help.
 

spec

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Hello elecLear78,

If you give us the following information we may be able to help:
(1) What stepper motor have you bought?
(2) How are you driving the stepper motor?
(3) What do you want the stepper motor to do, or are you just experimenting?

One of the simplest, cheapest, and most flexible ways to drive a stepper motor is to use an Arduino micro controller driving a stepper motor shield (input output board) which in turn drives the stepper motor.

You would then load a very simple program (called a sketch) from a personal computer (PC) via a USB link to the Arduino.

An Arduino runs from 5V so you would also need a 5V three terminal regulator (LM7805 for example) to convert your 9V battery voltage to 5V, but the stepper motor shield may run from 5V and 9V and the stepper motor may run from 9V, subject to what type of stepper motor you have bought.

spec

Arduino Uno clone: http://www.ebay.co.uk/ardunio_uno

Stepper motor shield: http://www.ebay.co.uk/itm/Useful-1-5A-Dual-Channel-h_bridge_motor_driver_L298

Introduction to stepper motors: http://www.solarbotics.net/library/pdflib/pdf/motorbas.pdf

(PS: my understanding is that a six-wire stepper motor has two center-tapped coils and that driving a six-wire stepper motor in unipolar mode means that you just ignore the center taps on each coil and treat the stepper motor as a four-wire stepper motor and drive each coil with a unipolar signal ie 0V to 9V say)
 
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I tried the following you tube video. I don't know much about stepper motor. Initially I want to see the motor moving and hence experimenting with 9v supply. As of now I did not connect anything to the motor.

 

spec

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You do not indicate what stepper motor you have bought. Just one thought: if the stepper motor is geared down, as many are, you will probably not see the shaft moving.

spec
 

Mickster

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(PS: my understanding is that a six-wire stepper motor has two center-tapped coils and that driving a six-wire stepper motor in unipolar mode means that you just ignore the center taps on each coil and treat the stepper motor as a four-wire stepper motor and drive each coil with a unipolar signal ie 0V to 9V say)
That would bipolar mode.

A 9v battery most likely does not supply enough current, unless the stepper motor is very small.

You will require a datasheet for the motor you are driving, in order to operate it at it's full potential.
Salvaged motors from office printers and such usually have custom numbers and sometimes Googling does not return an exact match.
Checking the 6 wires with a multi meter on Ohms will let you find the coils. You will have 2 separate centre taps and 4 separate coil taps.
Like this:
[email protected]@@[email protected]@@---B and also [email protected]@@[email protected]@@---D
A to D are the coil ends, @ is the coil and T is the centre tap.
As an example, you would get 1.2 Ohms from A to T and from B to T. From A to B would show 2.4 Ohms. This is one half of the whole motor circuit.
You would get the same resistance readings for C to T, D to T and C to D. There should be no connection from one half of the motor to the other half.

Useful links:
http://homepage.cs.uiowa.edu/~jones/step/
http://techref.massmind.org/techref/io/steppers.htm
 

Mickster

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Looks like a Nema 17 sized motor, is it roughly 42mm x 42mm?
 

Mickster

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If there is no label on the stepper motor indicating the required operating voltage and current, you will need to do some checks.
When driven using a chopper driver, the voltage is somewhere around 10 to 15 times higher than what is printed on the motor label.
Check the motor coil inductance to find the maximum voltage that the motor can be ran at using a chopper driver, then divide that by 15 to be safe
when stepping using a non-chopping driver.

To find the max voltage, use the formula Vmax = SQRT(L) x 32
Example:
Measured 3.2 mH coil inductance.
SQRT of 3.2 is 1.788854381999832 x 32 = 57.24334022399462 (or 57.24V)
Divide 57.24 by 15 and you get 3.816V

This is the data from a stepper I have a datasheet for and used for the example above ( U is unipolar, B is bipolar):
M60STH88-3008DF 1.8 DEG U=3.9V/3.0A B=5.46V/2.1A
U - 3.200 mH 1.3 Ohms per coil 57.2V
B - 12.80 mH 2.60 Ohms per coil 114.5V

Dividing the Vmax by 15 works for unipolar mode as you can see above, but not for bipolar. The bipolar result needs to be further divided by 1.4 to reach
what is printed on the label and I don't know why, but I'll bet Spec does.

Anyway, for the current of an unknown stepper motor, it's best to start low and check the heat of the stepper motor body. If it is too hot to hold for more
than a second, it's probably too high and needs to be reduced. I don't remember where I read that, but will see if I can find it again.

EDIT
Some more reading material:
http://www.mycncuk.com/threads/571-Investigating-unknown-stepper-motors
http://www.geckodrive.com/support/step-motor-basics.html
 
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Mickster

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The stepper you have in your picture sort of matches with these 2 on ebay, from the mounting plate attached.

Minebea 17PM-J204-G1ST:
http://www.ebay.com/itm/MOTORE-PASS...254896?hash=item462f7a4cb0:g:2yAAAOSwaNBUkcTv

Minebea 17PM-K207-P1ST:
http://www.ebay.com/itm/MOTORE-PASS...254955?hash=item462f7a4ceb:g:RA0AAOSw2XFUkcT6

The size fits for a Nema 17 type, but you will not find an exact match because those motors have been pulled from an office printer or similar.
The Minebea numbering system is explained in the datasheets, but as this is a custom stepper, like those above, exact details will not be found.
The best thing you could do to try and work out what you have, would be to look at the tables for Nema 17 motors and match up the body dimensions,
winding resistance & inductance, motor cap and total mass. Motor cap means the end plates - are they pressed steel or aluminium?
If you can match up those parameters, you are a lot closer to finding the best specs to operate with.

Check here for a Minebea datasheet:
http://cnc25.free.fr/documentation/moteurs pap/pap_nmb.pdf

There are plenty of examples out there for Arduino.
 

dr pepper

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You can use a meter to work out which 'side' is which, there are usually 2 coils, and a unipolar motor just has 4 wires for those 2 coils, bipolr motors have a centre tap on each coil so have 6 wires.
If you have a way to measure low ohms, like with a power supply, you can meter out the outer of the 2 windings and connect those up ignoring the center taps, the 2 outer connections to the windings will be the ones with the highest resistance, and the center tap will have the same resistance to the outer 2.
 
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