Hello! I'm in the middle of building an Arduino based CNC mill. I have too many motors for the control board to power in parallel- it would overheat instantly. I don't want to do it in series either. Is there a way to take power from a CNC power supply such as this one and distribute it evenly to power 14 NEMA 17's? I am new to electronics and struggling to figure out how I would step down power. I've looked at UBECs and DC-DC converters, I just don't know how to get all of the steppers powered with 4v 1a each. Any help would be appreciated!
How are you currently powering the motors?
I can power 8 motors off of an Azteeg X3 Pro. One for each axis and four for multiaxial tool manipulation.
How many motors for each axis then? 14 is a lot of motors.
You want to avoid series because of the lower top speed I presume?
calculate Imax by how many motors will be/can be running at any one instant, add a fudge factor.
acquire a supply which can support the required current and less than the max voltage of your drivers.
parallel the external supply to the Vmot's, connect all grounds (arduino and drivers' Vmot gnd).
what's the problem? besides 14 motors is a lot of motors...
check the spec.s for your drivers. You can supply, say 12V, to the driver when it is connected to a 4V stepper. You just have to set the current limit, the driver takes care of the voltage required.
4 For Z axis, 4 for Y, 2 for X. The reason I have so many is because the tool space is 2M3 (1x2x1). CNC mills need to be strong to mill materials like metal, and this is an extremely large build space. (It's also multiple tooled: 3D printing and laser cutting are tasks in sight as well.)
And yes, the low top speed is what I want to avoid.
123Splat, I don't completely understand what you mean. I need 4V per motor at 1 amp each for 14 motors . Does that mean I need a 56 watt power supply? Where would I get that?
Also, I don't have a driver. I have a multiple axis stepper controller.This is the Azteeg X3 Pro
I cannot pull that amount of power through the board. It is made for large machines, but my machine is still bigger.
that board has 'slots' for 8 drivers (they say SD8825, sounds like a proprietary version of the DRV8825 carrier). ie: you supply your own drivers (up to 8) with that controller board (the board has it's own MCU/'arduino').
as to power, do you plan on having all 14 steppers stepping at the same time?
you cannot drive 14 steppers through that board....
I will split the control signals between two motors on 4 of the board outputs.
Incidentally, the power given to the stepper just has to be a constant level, correct? Is the power a signal as well?
Maybe if I use a repeater?
Is there a way to use a breakout board for what I need?
I need 4V per motor at 1 amp each for 14 motors . Does that mean I need a 56 watt power supply? Where would I get that?
Stepper motors are current controlled. They need 1 amp each. The voltage and the power depends entirely
on how fast you want to go.
But its more complicated than that - the 1A is the phasor amplitude - the worst case of 45 degrees needs
0.7A for each winding, ie 1.4A in total.
Thus 14 motors need 20A of drive in total.
However stepper drivers are power converters - they are basically constant-current buck converters so
that the output current can be much higher than the input current.
If your motors are 4 ohm, 1A, then the dissipation is 4W per motor, allowing for driver losses etc that
means budgeting ~6W per motor (and that's only to keep them stationary).
Once motors have to move the buck conversion demands more current from the supply.
You probably need a minimum of 100W 24V supply, more power will allow more speed, more voltage
might be needed too then.
whew I thought people were beginning to give up on me :o ! Thank you for the help!
So what power supply should I buy? A 24v, what amp measure? 20a? Or more? I don't want to fry my motors...
Also, how would I connect the motors to the supply? I think I may have a piece of solder breadboard with two rails, and just line the motors down them. Is this viable?
Thank you so much for the info !
I am very curious how you are able to sync the movement of all the stepper motors in each plane? The reason I ask is we have a CNC selective soldering machine that has a large platform that is controlled in only the "Z" plane. It has one stepper motor driving a cog belt with 4 matching pullies attached to leadscrews on each corner.
A few years the belt had worn and stretches so one pulley slipped a notch. This made the able tilt a bit and bind. Eventually we discovered the problem and adjusted the mounting of the stepper motor.
With more than one stepper per axis, starting from a "zero" point must be pretty exciting.
@Paul_KD7HB, 3D printers already do this. I have never run into a problem where the Z axis motors did not line up. The Z axis motors are the only ones that are not linked together. They don't move nearly as much as the other axes do either. I'm not worried about that.
Does anyone know the power rating of the supply I should get, and how to connect it (as queried in my previous post)?
Does anyone know how I would power four of these? I'm having the same problem here...