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  1. #11
    I don't want to go into the technical detail (it's been done before on the forum!) but in hand-waving terms, stepper motors need current because it's current, not voltage, that generates a magnetic field. However, to push lots of current into the coils in the motor, you need plenty of volts to get it flowing. One of the jobs of the stepper driver is to take whatever voltage it is supplied with, and use that to push current into the motor windings. It will regulate the voltage applied to the motor to get the right current and stop it going over the set value (that is, the value that you have told the stepper driver to use). However, if there isn't a high enough supply voltage, it takes longer for the current through the windings to build up to the right value, so smaller magnetic fields, so lower torque available. My power supply is about 68V because that is about the highest that it is safe to use with my M752 drivers. I haven't tried a lower voltage so don't know from personal experience how much difference it would make. In any case, my MDF machine is not capable of particularly high speeds, so it wouldn't be a good test. I over-specified the motors and electronics for my first machine as I had a feeling that I would be upgrading eventually and could then re-use them. This description is also why the voltage you use with the drivers is way, way, over the nominal "max volts" specification that you will find on a stepper motor spec sheet. Don't worry about it - the driver will sort it out as long as you don't go over the motor's current rating.

    You also have to watch for overloading the drivers. Under certain circumstances, the motors will generate a reverse voltage that gets added to the supply voltage that the driver sees. Your power supply is 36V and the max supply for the drivers is 50V, which should be fine.

  2. #12
    Ok Neale is correct regarding the steppers and current etc. But if you want to future proof your electronic to use on another machine then the drivers you have chosen are not good enough.
    You would be better buying the steppers from cnc4you and using AM882 or EM806 (the newer version) but the AM882 are fine and cheaper as they both can take up to 80 V so then you would need a 70V power supply for them.
    The difference between 36V and 70V is night and day. It is one of the biggest mistakes that people do with using underpowered drives. ..Clive
    Last edited by Clive S; 02-03-2015 at 06:59 PM. Reason: Sorry spelt name wrong

  3. #13
    Can't disagree with Clive - new machine is being upgraded to EM806 for X and Y. As I said, I doubt if the lower voltage would have been an issue for my current router but that's because it's a pretty ropey machine. New machine deserves better and will get the higher voltage.

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