X2 Mini Mill Build with Digispeed Spindle Control and USBCNC MK3 controller.

I am posting this in part for my own reference as well as others who might need just a little help in figuring it all out. I am using the CNC Fusion Ball Screw Kit, which is working fantastic, and 425 oz/in motors from long's with DM542A drivers on 3 axes at 36 volts and 2.84 amps. For the CNC controller, I am using USBCNC and planet-cnc's 9 Axis MK3 USB/Ethernet CNC control board (I have a 4th and 5th axis U-table that is a mess from Ebay, but the price was fair). For spindle and spindle control currently, I am using the stock Harbor Freight mini mill spindle motor with a LMS pulley system and the Z-Axis is partially supported by the gas tube kit that LMS sells to reduce pressure on the motor when moving the spindle assembly against gravity. Spindle speed is controlled by the MK3 controller connected to a Homann Designs Digispeed DC-05 motor controller without the optional onboard 5V to 15V DC isolated voltage generator. So this is where it gets a little tricky, and much of the documentation available only hints at how to connect this whole mess and those connections are critical with regards to maintaining opto-isolation of the ground. The process of connecting the motor is potentially dangerous due to the voltages and potential amps involved, sufficient to cause death under bad circumstances, should you inadvertently set yourself or others in the path of the current flow.

So here it goes, removing the rear panel of the machine motor controller there are 3 connections you attend to P1, P2, and P3. They will need to be connected to the Homann DC-05 to control the motor.

P1 is the reference voltage and connects to AV+ on the DC-05 connector J2
P2 is the speed signal (0-5v iirc on the mini mill) and connects to Vout on the DC-05 connector J2
P3 is the floated ground and connects to AGnd on the DC-005 connector J2. *** IT IS CRITICAL THAT IT CONNECTS NO WHERE ELSE ***

From the USBCNC MK3 controller to the Digispeed DC-05

The MK3 output block is a 10 pin connect with the 8 programmable outputs and one connection for power on Pin 9 and ground on Pin 10.
In my case, I configured the USBCNC outputs as follows:
Pin 3 Spindle Enable,
Pin 1 Spindle Speed with the following options Min speed 1000 rpm (it does not appear to matter, probably should be 0) and max speed 6000 rpm
USE PWM checked and base frequency 1000 Hz

Connect Mk3 pin 1 to the DC-05 Sig pin on connector J1 (This controls the actual speed of the motor
Connect Mk3 pin 3 to the DC-05 RL1 pin on connector J1 (This enables the DC-05 as evidenced by the solid red LED on the board)
Connect Mk3 pin 9 to the DC-05 +5v pin on connector J1 (power to run the DC-05)
Connect Mk3 pin 10 to the DC-05 Gnd pin on connector J1 (obviously the ground for the DC-05)

Now for the non-obvious part. The spindle motor control panel potentiometer needs to be in the completely off position (otherwise the motor will not spin). I believe that otherwise the potentiometer grounds the entire circuit through the resistance offered (my potentiometer is no longer connected to the connections on P1, P2, and P3). I need to completely remove the potentiometer from the system at this point, but neglected to look at all the connections in order to do that yesterday. There is always potential that this configuration is dangerous, but I sincerely doubt it, but you assume your own risk should you follow my directions. I hope this is helpful to anyone with a similar configuration. I am planning to replace the current motor with one or more of the following:

200v 3 phase 750w Yaskawa servo motor SGM-08A312 with an SGDH-08AE-S servopack and NS600 indexer (which with any luck I can make work).
1500w 24volt RC aircraft motor powered by a 24 volt 75 Amp DC power supply with an encoder.

For tooling, I have the R8 spindle and a variety of R8 tools, but I am also setting up a number of tools "tormach style" with ER-16 collets and 10 straight shank 3/4" collet holders.

I am also in the process of converting my mini lathe to CNC as well.

Mark

Hi Mark,

Good to see you have it working.
The potentiometer you have removed connects to P1,P2 and P3. The lead that connects to the centre of the potentiometer connects to P2 on the speed controller board.

If you turn the knob on the removed potentiometer fully CCW, then measure the resistance between the centre lead any any one of the other two leads. If the measured resistance is almost 0 ohms, then that wire will connect to P3 (Speed controller floating GND). The lead at the other end of the Potentiometer will then connect to P1.

If you get the two end wires wrong, the speed controller will run at max speed when fully CCW instead of when fully CW. If this is the case, you can swap the P1 and P3 leads over.

As always be careful when playing around with the motor controller electronics. The voltage on P1 is at mains potential, and the voltage at P3 (floating ground) is around 10V-15V below mains potential. Both are lethal.

Cheers,

Peter

Thanks Peter, it does work rather well and was pretty easy too get working. I started playing with the outrunner motors today, as I picked up some small cheap ones for proof of concept. These little motors are pretty amazing beasts for the price and the power consumption. I have two motors running at 12 volts each. One is using a 30 Amp RC motor controller and the other is a 100 Amp version which I got from Hobby King. One is the ST4010 and the other is the ST3511. For a $10 motor, the ST4010 is pretty savage - the small one is rated at 300W and the larger one at 680W. Although they seem somewhat lacking on overall torque at lower speeds, I suspect that with the proper setup that these motors could be rather suitable to the task of turning a spindle when geared down or a more appropriate motor is selected for running the spindle.