Centroid Community CNC Support Forum

Hey all! I recently picked up an old Dyna Myte 2400 mill:
It's mechanically all there but has been stripped of all of it's electronics. I have a drive system (and motors) already waiting to go on it so in terms of moving XYZ I've got that covered.

What I'm curious about is the correct approach for the spindle. Right now it's got it's original 80V 1/2 HP DC spindle motor in it, and the previous owner had this box hot wired into it:

This seems to work fine, but my goal is to have this spindle controlled by the Acorn, not manually using this box.
For reference this is the motor:
I've been looking around to see how others have tacked this problem, and the closest thing I can find is this build from Franco:



I've done my fair share of conversions, but I have never dealt with a DC spindle motor (only VFDs and 3 phase spindle motors)

Given that this motor works fine and is nicely integrated into the head of this machine I would like to reuse it. Has anyone here done something similar and could help me understand how this should work?

My thinking is there has to be something that can take the Acorn's 0-10 volt output and translate that into a PWM signal for this motor by way of some kind of control box...

I think you should find out what the current or power rating of that motor is and then find a DC motor drive to match. They are not hard to find, AutomationDirect has some options here https://www.automationdirect.com/adc/ov ... _dc_drives

Edited: On further reading, it seems that those drives would require the analog voltage input card accessory to let the Acorn control the speed. There may be some available elsewhere with that functionality built in.

Supposedly it's a 1/2 HP motor.

So I'm wondering if this:

https://www.automationdirect.com/adc/sh ... sd4-240-5c

Combined with this:

https://www.automationdirect.com/adc/sh ... gsda-ai-v4

Would work. The first DC drive it looks like I can limit the voltage down a bit to get it close to 80v, and with that little accessory board it can use 0-10 volts to control the speed of the motor.

This one isn't reversible though, not sure how much that matters on a mill like this. I have machine a decent amount of aluminum on my router and never really needed reverse...

I am not sure about reversing but they have a manual reverse switch available. It might be possible to replace that with a relay arrangement.

That accessory board will let you use 0-5 to control the speed with that drive. It seems like other series of their drives might have 0-10 with the corresponding add on board.

Good catch on the 0-5 volts, some of the others I was looking at with the daughter board were 0-10.

I find this little guy:

https://amzn.to/4aV2M1t

I might just give this a shot given it's pretty inexpensive. I bet I could get reverse working with a couple of relays.

I'm now wondering if it would be worth putting an RPM sensor in this setup too. I assume Acorn could detect the commanded RPM vs the actual RPM and compensate?

Toaster wrote: ↑Tue Apr 16, 2024 9:07 pm
I'm now wondering if it would be worth putting an RPM sensor in this setup too. I assume Acorn could detect the commanded RPM vs the actual RPM and compensate?

Nope, CNC12 does not close the loop on spindle speed control.

CNC12 will show you the actual RPM via the encoder feedback but, its up to you to calibrate the speed controller so when CNC12 asks for 1000 rpm the speed controller does it.

and in case you are wondering, Rigid tapping works by chasing the spindle encoder position with the Z position, not the other way around.

Ok interesting... I may still rig up an encoder