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  1. Good day all.

    I would like some help and advice with regarding to wiring up my new M60STH88-3008DF Stepper Motors to my PM752 Stepper Drivers.

    Is it best to wire the steppers in Parallel or Series mode.

    My understanding is that it's best to wire the steppers in parallel mode for more speed.

    And I am having problems following the stepper motor data sheet on how to wire the steppers to my drivers.

    PM752 Stepper Driver Output
    A+
    A-
    B+
    B-

    M60STH88-3008DF Stepper Motor Wires
    A+: Blue/White
    A-: Blue
    C-: Red/White
    C+: Red
    B+: Green/White
    B-: Green
    D-: Black/White
    D+: Black

    I was looking at wiring the steppers and drivers as follows.

    A+ > Blue/White & Red/White.
    A- > Blue & Red.
    B+ > Green/White & Black/White.
    B- > Green & Black.

    Can anyone please confirm if this is right?

    Thanks for your time.

    Best Regards.
    Last edited by Mad Professor; 11-08-2011 at 01:25 PM.
    "If first you don't succeed, redefine success"

  2. #2
    Yes, parallel in general is best.
    Incorrect...

    EDIT: THIS IS COMPLETELY WRONG!! Ignore me.

    A+ > Blue/White & Blue
    A- > Red/White & Red
    B+ > Green/White & Green
    B- > Blact/White & Black

    You'll notice that the similar colours go together (remember that and you don't need to look at the instructions!)...if you swap either of the phases round the motor will spin the other way, so it's not an issue.
    Before you switch the power on check the motors spin freely, as if so you've probably done it right...
    Last edited by Jonathan; 11-08-2011 at 05:20 PM.

  3. #3
    Presumably you decided on parallel/series when you bought the PSU? :naughty:

    Question is:- Is the high speed torque increase from wiring in parallel worth the extra heat you have to dump into the surrounding metalwork?

    OTOH, if your PSU has the legs, it costs you nothing to suck it and see :tup:

  4. #4
    The correct way to wire in parallel is as follows.

    A+ Blue/White & Red.
    A- Blue & Red / White
    B+ Green /White & Black
    B- Green & Black / White

    The easiest way to remember is to put A phase on top of C phase and B phase on top of D phase.


    Quote Originally Posted by Jonathan View Post
    Yes, parallel in general is best.
    Incorrect...

    A+ > Blue/White & Blue
    A- > Red/White & Red
    B+ > Green/White & Green
    B- > Blact/White & Black

    You'll notice that the similar colours go together (remember that and you don't need to look at the instructions!)...if you swap either of the phases round the motor will spin the other way, so it's not an issue.
    Before you switch the power on check the motors spin freely, as if so you've probably done it right...

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  6. #5
    Quote Originally Posted by Jonathan View Post
    Yes, parallel in general is best.
    Incorrect...

    A+ > Blue/White & Blue
    A- > Red/White & Red
    B+ > Green/White & Green
    B- > Blact/White & Black

    You'll notice that the similar colours go together (remember that and you don't need to look at the instructions!)

    .
    NOOOOOOOOOOOOOOOOOOOOOOOOOOOO ??????????????????????????????????

    Blue / white and Blue is a dead short
    Same for all the others.


    Gary is correct, so is the mad professor.
    There are 4 ways to wire in parallel, all are correct but the motors will spin different ways.
    Last edited by John S; 11-08-2011 at 04:27 PM.
    John S -

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  8. #6
    Whoops, sorry that was stupid! Never got it wrong on mine ... not sure why I put that.

    At least if someone had followed that they'd have hopefully been saved by me saying try spinning the motor by hand. Still a totally unacceptable error.

  9. Need some help please on understanding the max current for these M60STH88-3008DF stepper motors. We have a PM542 driver that allows different currents to be set. Having read various threads and reviewed the motor calcs spreadsheet I still don't understand how to get from from the motor datasheet voltage-current values to real world values. For example, with this M60... motor the data sheet values are:

    Wiring mode: bipolar series we've wired like this
    voltage: 5.46 v
    current: 2.1 A
    resistance: 2.6 ohms
    Inductance: 12.8 mH
    Holding torque: 3nm

    Obviously V=IxR works for the figures above; but in the real world I'm using 43vDC.

    So what's the max current I should be using given my 43v supply and why am I using 43v when the data sheet says 5.46v?

    Thanks

  10. #8
    You should set the drivers to the setting closest to (but not greater than) 2.1 amps. If you had wired them in bipolar parallel (presumably you have your reasons for not doing this) then you would set the driver to 4.2A.

    The reason Ohm's law does not immediately appear to apply when using 43v is the current is pulsed, not contsant. The drivers use PWM (Pulse Width Modulation) or chopping techniques to limit the current to the motor. If you did apply 43v to the motors constantly it would quickly destroy it as that is 62 times the rated power!

    You are using a higher voltage since the inductance of the motor limits the rate of change of current through the motor, and increasing the voltage counters this. Using a low voltage will limit the maximum current that can get to the motor at high step rates (since there is only a finite time for the current to rise before it is cut off at the next step), thus limiting the torque.

    For an ideal inductor v(t)=Ld(i)t/dt
    Rearrange that for d(i)t/dt:
    d(i)t/dt=v(t)/L

    We want to maximise the rate of change of current, so clearly the formula above shows that increasing the voltage or decreasing the inductance achieves this. This is why you should buy motors with the lowest inductance you can find. Putting the motors in bipolar series increases the inductance, as inductors add in series ... so in parallel the value is a quarter of the series inductance. This may explain why the torque is slightly reduced at high speed with bipolar series, though I'm only guessing.

    (There's a bit more to it than that in reality, but that's the general idea.)
    Last edited by Jonathan; 31-08-2011 at 08:15 PM.

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  12. #9
    Quote Originally Posted by Karl View Post
    So what's the max current I should be using given my 43v supply and why am I using 43v when the data sheet says 5.46v?
    As Jonathan says, you need it to overcome the inductance of the motor windings.

    Inductance tells you how unwilling a circuit is to change the flow of current. It's all about building up and collapsing magnetic fields.

    You apply 43 Volts and the current in the coil changes a jolly sight faster than if you applied 5.46 Volts. This is really useful if you want to reverse the current in a stepper coil umpteen times a second.

    When it switches the current off, the coil doesn't want to stop flowing current. If you don't give that current somewhere to go the volts will simply rise until a transistor blows or ithe arcs to ground. Seriously bad idea. The fix is to allow the current to flow back to the start of the coil, round and round until the coil resistance turns it in to heat. Thus the coil inductance is a double whammy, it gets you when you turn the power on and when you turn the current off.

    Luckily the driver sorts it all out for you. Some are cleverer than others though. Ignore everything on the motor label except the current.

    Of course what you really need is the graph which shows motor torque over a speed range for a given current and voltage. Unfortunately the sellers of stepper motors have realised that the only thing their customers seem to care about is the holding torque so that is what they sell you. Who cares if the torque nose dives at 5rpm? It's a 3Nm motor, has to be good, dunnit!

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  14. Thank you folks; most useful. Now I can't immediately remember the really good reason why I chose to wire the motors as bipolar series (there was one) but there seems to be a suggestion that bipolar parallel would be better(?). So off to find and read a thread on bipolar-series v -parallel wiring. Thanks again.

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