PWM Spindle Control using Mach3 - How I did it

[chrisjh]

Hi All,

I see a lot of queries, especially from novices, regarding methods of Spindle Control.  There are a lot of topics covering this but most do not give a full explanation with examples in one place.  

What I have tried to do is put a lot of scattered info and the benefit of my own personal experience into one document.

Please take advantage of my experiences at www.cjh.com.au//PWM Spindle Control using Mach3.pdf

Regards

Chrisjh

[Tweakie.CNC]

Excellent work Chris, a well prepared document which I am sure is extremely useful to us all.

Tweakie.

[RICH]

Thanks for the write-up Chris.
I have created a new thread in Members Docs titled Spindle Speed Control and have posted your document there.
It is nice to have some focused documents on subjects. Those documents can save users a lot of time since sometimes you need to have
a grasp ( or maybe total read of the manuals ) to get what you need to know.
 
RICH
 

[budman68]

Very nice work, Chris, thanks for sharing-

Dave

[khalid]

thanks  Chris.. It is useful to all of us.
Regards

[airnocker]

Thanks Chris for a great, well documented explanation on your Mach3 spindle speed control.  This information was extremely helpful to me.

Best,

[Peter Homann]

Hi Chris,

Unless I've understood incorrectly, There doesn't appear to be any opto-isolation in your PWM to voltage converter circuitry. If this is the case you are relying on the VFD or speed controller having opto-isolation on its input.

If your circuit is connected to a VFD or motor controller input that is not isolated from the rest of the outputs connected to the same supply, you will most likely fry whatever is connected to these other outputs.

At the very least you need to put in a warning in your documentation. Otherwise some of the novices you are trying to help wont be happy.

Better still, replace T1 in your circuit with an opto-isolator and make it clear that the Gnd and 12V supply comes from a separate isolated power supply.

Otherwise all good info.

Cheers,

Peter.
 

[chrisjh]

Hi Peter,

The input to T1 on the PWM Converter is channelled through an Opto Isolated C23 Breakout board.  The Output to the VFD is as recommended by Danfoss documentation.  The PWM converter is powered by a 12VDC supply which is used only for the PWM Converter and a workspace illumination lamp.  All power supplies (5VDC, 12VDC and 42VDC) are all securely grounded to the chassis on the -ve side. 

I am a firm believer in having all supplies grounded to the chassis on the negative side as it make things safe and easy to troubleshoot.  I believe that isolated, floating power supplies introduce problems that are difficult to faultfind when things go wrong.  I have a Syil CNC Mill that has multiple isolated supplied with at least 2 separate grounds.  It is a right menace to faultfind and is downright dangerous to work on because of isolated, non common grounds.  It was because of this poor design that I deliberately designed my lathe to make it safe and easy to work on.

Regards

Chrisjh

[Peter Homann]

Chris,

The output you are using pin 14 on port 2 uses the same supply as pin 1, 16, and 17 on port 2. So if you try to use a VFD or DC motor controller such as the KBIC-120, with a non-isolated analog control voltage input, the 0V terminal is likely to be at supply((110V) - 10V. If that is the case, there will be serious damage if these other inputs are referenced to chassis ground.

If the VFD or DC motor controller has an isolated or ground reference input as is the case with your Danfoss VFD, then yes your circuit will work.

You should still make it clear that your circuit will not work with non-isolated VFD or Motor controller inputs.

Cheers,

Peter.

[airnocker]

Chris, what Mach3 Kernel Speed are you running to have the PWM Base Frequency set to 500?

Thanks