help on stepper controller

Discussion in 'General Electronics Chat' started by Michael5139, Sep 17, 2010.

  1. Michael5139

    Thread Starter New Member

    Mar 9, 2009
    2
    0
    Hello,

    I have a controller for stepper motor for different speeds that broke.
    it has 4 outputs (no ground). apparently for 2 coils.
    when it was working it was outputting the signals ive drawn in attached image.

    slow speed:
    http://img521.imageshack.us/i/speed1e.png/
    faster speed:
    http://img684.imageshack.us/i/speed4.png/
    Now it's working 2 times fater then needed. And i dont know what the problem is.
    If i'd make a new controller - how can i drive the 4 lines? is there an IC which can be used for this purpose?
    how the speed can be altered in this kind of step motor?

    thanks.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Look at a stepper driver like a Motorola/ONSemi MC3479.

    Your first waveform looks like that of a unipolar stepper driver.

    The 2nd looks like that of a bipolar stepper driver.

    They are not exactly compatible.
     
  3. hspalm

    Active Member

    Feb 17, 2010
    201
    8
    A stepper motor with only 2 coils would make it a 180 degrees stepper motor, so I bet it is 2(bi)-phase with several coils per phase!

    Jokes aside. I am not an expert on this. But have you tried the controller with several stepper motors? Unipolar ones have 5 wires or more, and would good with the first waveform you posted, connecting the 5th (common) or both 5th and 6h wire to ground or power, depending on if the controller is sinking or sourcing current.

    I think your second waveform looks like bipolar mode microstepping, but I might be wrong here. Is it possible that you can switch the mode on the controller between bipolar and unipolar? Why the pulse width is so different I have no clue, but this shure sets the speed of the motor...

    An IC to control a bipolar stepper motor would be the L293D double H-bridge driver, but it can only handle 1A, so depending on your motor this may not suit your needs. For driving a unipolar motor you simply use a multi-darlington array driver, as you don't need to turn the current directions on these motors.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Just to clarify...

    A bipolar stepper motor has 4 wires.
    Unipolar stepper motors have 5 or 6 wires.
    Universal-type stepper motors have 8 wires; they can be wired for use as unipolar or bipolar steppers.

    BLDC (Brushless DC) motors also have 4 wires. It's easy to confuse them with bipolar stepper motors. One quick way to determine what you have is to measure the resistance from one wire to the other three wires; a BLDC will show continuity to all 4 wires, while a bipolar stepper will only show continuity to one other wire.

    Here's an example of how BLDC motors are connected internally:
    [​IMG]
     
  5. Rbeckett

    Member

    Sep 3, 2010
    205
    32
    Stepper motors are actually very easy to control once you determine exactly what you are trying to drive and how you want to drive and decide speed and direction. 99% of all steppers are plated with degrees per step, amps, and Ohms as well as any number of wires protruding from the case. If you will read the data plate and measure each wire you will see the patterns and then a simple Picaxe or similar device can be built to control anything you wish it to do. There is a source about steppers called "Jones on steppers" from the Univ of Iowa and it is the definitive document for any one who desires to use on in any application. If you need additional assistance, LMK and I will send you links to the source of any stepper info you may need, since my current field of interest is stepper motor devices. Hope this helps.
    Bob
     
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