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Need help with a Uni Polar Motor — Parallax Forums

Need help with a Uni Polar Motor

blacksheep45blacksheep45 Posts: 41
edited 2009-04-20 09:06 in BASIC Stamp
Hello,

I am currently trying to connect a 48V unipolar motor to a BS2. I am using a ULN2003 darlington array driver chip. The wiring for the motor is as follows:

Phase 1 = Orange
Phase 2 = Black
Phase 3 = Red
Phase 4 = Yellow

The common wires are (Orange & White and Black & White) and (Red & White and Yellow & White)

I have connected the motor to the driver chip as can be seen in the attachment

The two common wires are blue and green because it was easier to do than having several different colours for the same wire.

The motor also has its own 48V, 5A·power·supply. The V+ of the supply is connected to the com pin of the driver chip and the V- is connected to ground.

When i try to run the program (the stepper motor program from the parallax website changed to use pins 0 - 3) both the driver chip and the basic stamp blow.

Can anyone help me with this?

Kind Regards

Shaun
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Stepper Connections.bmp
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Comments

  • kelvin jameskelvin james Posts: 531
    edited 2009-04-14 23:04
    You might want to check out the current specs for your motor. The uln2003 can only handle 500ma per output.
  • blacksheep45blacksheep45 Posts: 41
    edited 2009-04-15 09:04
    Hi Kelvin,

    I realize that the driver chip can only handle 500mA and my motor is trying to draw 4.5A per phase, but should this cause both the driver chip and the stamp to blow? as I was told by the motor manufacturer that if there was not enough current to be drawn the motor would simply not move.

    Also I was wondering if anyone knew where I would be able to get a high current driver chip, preferably 5A or over.



    Kind Regards



    Shaun
  • stamptrolstamptrol Posts: 1,731
    edited 2009-04-15 11:56
    You have no isolation or current limiting back to the Stamp. So, when the uln2003 blows (as it will do because its grossly overloaded) its very likely the motor supply gets tied to the stamp pins and there goes another chip.

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    Tom Sisk

    http://www.siskconsult.com
    ·
  • blacksheep45blacksheep45 Posts: 41
    edited 2009-04-15 14:02
    So if I put diodes between the stamp and the driver chip that should stop the stamp from blowing.

    regards

    Shaun
  • stamptrolstamptrol Posts: 1,731
    edited 2009-04-15 16:31
    The fundamental problem is the uln2003 is overloaded and will continue to blow. Can't really see the value in designing that way.

    If you've got lots of uln2003's to get rid of, you should opto-isolate the stamp from the driver chip.

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    Tom Sisk

    http://www.siskconsult.com
    ·
  • blacksheep45blacksheep45 Posts: 41
    edited 2009-04-16 09:30
    How do I opto-isolate the stamp from the driver?

    Or would I be better off using another driver chip?



    Cheers

    Shaun
  • stamptrolstamptrol Posts: 1,731
    edited 2009-04-16 12:19
    Or, use the uln2003 to drive some power MOSFET's (IRL520, etc) to boost your current capacity.

    You can Google "high power stepper driver" to get some idea of what's involved.

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    Tom Sisk

    http://www.siskconsult.com
    ·
  • blacksheep45blacksheep45 Posts: 41
    edited 2009-04-20 09:06
    Would using the ULN2003 to drive power MOSFETs still work even though there is a 48V 5A power supply connected to the ULN2003. The power supply won't blow the driver chip because of it's high current, will it?
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