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UCN5804 stepper driver replacement

Discussion in 'Electronic Basics' started by aman, Apr 12, 2005.

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  1. aman

    aman Guest

    I am looking for a unipolar stepper motor driver. UCN5804 was a popular
    one for this but is discontinued. Does anybody know of any other
    unipolar drivers.

    Can I use a bipolar driver and add some diodes to enable unipolar
    operation. Any help would be greatly appreciated.
  2. Chris

    Chris Guest

    Hi, Aman. The UCN5804 is still available at alltronics for $5.50 a

    If I was to try something else, I'd use a PIC and a ULN2003 if coil
    current was less than 1/2A, or a PIC and four TO-220 NPN darlingtons
    with eight resistors and diodes if more than 1/2A coil current. Here's
    what one half of one of the stepper coil drive would look like (view in
    fixed font or M$ Notepad():

    ~ VCC
    ~ VCC +
    ~ + |R
    ~ | .-.
    ~ D| | |
    ~ - | |
    ~ ^ '-'
    ~ | ___ | ___
    ~ o-UUU-o-UUU-o
    ~ |
    ~ o---.
    ~ TIP120| |
    ~PIC ___ |/ |
    ~ o-|___|- -| |
    ~ 4.7K | |> |D
    ~ .-. | -
    ~ | | | ^
    ~ 4.7K| | === |
    ~ '-' GND |
    ~ | ===
    ~ === GND
    ~ GND
    created by Andy´s ASCII-Circuit v1.24.140803 Beta

    Here's a link that offers a veritable plethora of stepper driver ideas,
    including control through the parallel port of the PC using CQBASIC

    Good luck, and have fun
  3. aman

    aman Guest

    Thanks Chris. That is really helpful. I can see that UCN5804 is
    available right now. But if it is not available 3 months from now my
    design will fail. I need a design that i can sustain for atleast 2 more
  4. Chris

    Chris Guest

    O.K., then. If the chip really fills the need, buy a few spares. But
    if it bothers, how about some more information, like:

    * Is this a new design, or are you trying to fill an existing IC

    * Stepper coil current and voltage? Straight coil voltage or L-R?

    * Maximum stepper speed?

    * Do you need all the logic capabilities of the chip?

    * If not, which ones do you need? Read the data sheet carefully.

    * Thru hole OK or SMT only?

    * Do you have any capability with PICs or other microcontrollers?

    * List in order of importance: ckt board space, number of chips,

    * Beyond the IC itself, there's another issue. What's the rest of
    your control system look like? If you're using a computer, it would be
    simple to offload the logic requirement for which phases should be on
    to the existing computer, and it just becomes a ULN2003 or four
    darlingtons, depending on current/voltage requirements.

    That should be enough to start with. There are other stepper ICs out
    there, although you probably won't get a one chip solution like the
    Sprague IC.

    Please answer all of the above (middle post in the spaces provided if
    you want) and you could get an answer that works well.

  5. aman

    aman Guest

    Thanks Chris for the guidelines. That helps a lot.
  6. Externet

    Externet Guest

  7. aman

    aman Guest

    Thanks Externet. But these are all for bipolar motors.

    Can I use these to drive unipolar motors?

    Also, is microstepping different from normal stepping. Can I use any
    type of stepper motor with it or there are special motors for
    micro-stepping ?
  8. Chris

    Chris Guest

    The new Allegro chips are for bipolar drive, not unipolar. As an extra
    added bonus, they're only available in SOIC packages, which can be a
    pain for most newbies/hobbyists.

    Microstepping is a lot different than normal stepping. For a
    discussion on all things stepper motor, see the ultimate web reference,
    Jones on Stepping Motors:

    After you're done reading that, you have to take a good look at your
    application, and the data sheet for the Sprague chip you originally
    wanted, and answer some of the questions in the post above. You have
    to state what you need in order to get a good answer. Otherwise,
    people will just be thrashing around trying to guess, and lose
    interest. You and we will have wasted our time.

    If all you need is a single-step, low speed indexer/driver, your
    solution may be as simple as several TTL/CMOS logic ICs and four
    darlington transistors. But we have to know what you need first to
    replace the Sprague chip to help you.

    Time to learn and work a little to get what you need! ;-)

    Good luck
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