Simon

start by going to Config Ports & Pins Motor Outputs go down the list on the left until you get to the Spindle tab then Enable the Spindle with a green tick.

Fill in the pin numbers you have used for the Step and Direction pins and the port number (usually Port 1 for both Step and Direction) click Apply and the OK.

Go to Config again select Ports and Pins then the Spindle Setup Tab.

In the Motor Control Box tick the box at the side of Spindle Motor Output and also the box at the side of Step/Direction Motor click Apply then Ok.

Again go to Config Motor Tuning select the Spindle Tab.

Set the Steps Per to 1000 Velocity to Max start low on the Acceleration, set the Step Pulse to 3 to start with, this will affect the analog output voltage so you can come back to this when you do your final tweaking. Click on Save Axis then Ok.

From here on in you will have to read the info that came with your board, you might have a trim pot that you can adjust to give you your max output voltage to your motor control unit.

What sould happen now (do not connect your spindle to your board yet) when you give an M3 command in Mach you should get a voltage output from the analog pins on your spindle board.
Lets say your Max speed is 12000 RPM if you type the command S12000 then press enter in the MDI screen in Mach followed by a M3 command you should get the max voltage output, if you then type in S6000 you should get half your max voltage. If the voltage is lower then this is where you can tweak the step pulse width and the trim pot (if you have one) to calibrate the output voltage.

Hope this helps

Regards

Andy

PS the board I am using at the moment is the PMDX 126 BOB with the PMDX 107 speed control. This is a PWM system you don't need any relays to switch the spindle on it uses the PWM signal to switch on the spindle as well as set the speed and it works very well.