Mach3 step pulses can be converted to an analog voltage using a digital potentiometer.  We are currently doing this for our laser diode drivers to modulate laser power.  http://www.picengrave.com/Laser%20Setups.pdf

Maybe our circuits can be used for controlling servos, too.

John Champlain

Do you have encoder feedback John, Is there a way to close the loop with that feedback?
Hood

Hood,
I thought all that was done by the servo controller, and all that would be needed would be for Mach3 to supply an analog voltage to the existing controllers.  I didn't mean to add noise to this discussion.
John

No problem John, I was curious if your circuits could do that and was asking.
With a position type drive then yes all that is handled in the drive but the drive will take Step/Dir or CW/CCW or be set up as Encoder follower.
For an analogue amplifier or drive to close the position loop your control has to do that, ie the control reads the encoder position and feeds the drive/amp with analogue commands to move it or keep it where it is, ie the controller has to close the loop.

Hood

Your best option is as I said at the start, get a controller that will work with Mach and output analogue +/- 10v control signals to your amps.

CSMIO/IP-A is what I use.
There is also
DSPMC
Kflop with Kanalog
Galil
and there is also a DIY option, YAPSC, but I have heard of varying results from it, from working ok to not working at all.


Hood

oK THANKs for quick response

And what about second option i asked? can i just plugged some pot and give fix value to Axis drives to run at fixed speed? My client is not going to run machine for full application. He needs only 1-2 specific Jobs to work on

Regards,
Devesh Vithani

You can have a pot connected to the axis but you will not have any real control over the position, it would be fine for a spindle but not an axis. Even load would affect things as there will not be any closing of the loop for position so I would say you need to either try and do it on the cheap by trying the YAPSC or use one of the proven controllers.
Hood

Is this step pulses are PPM??

Sorry dont know what you are meaning.
Hood

Please have a look at this attachment

I am thinking to use something like this. Step will be converted to PWM as shown. Does it looks OK? and then this PWM can be converted to analog easily using card I already have. I am not able to take test as of now because i am waiting for SSR so that i can hook up this 5V Step pulse to PLC which required 24V as input

Only catch is speed of Input. PLC requires 13ms for changing state from 0-1. Does this OK? what is the time range for this Step pulse signals? I mean how many pulses will be there in say one min or what is the max and min frequency of these pulses?

If you are wanting to have any kind of precise positional control over an axis, let alone multiple axes then trying to do it via PLC and Mach or any other method you have mentioned, is wasting your time.
If you want to simply have positional control to set positions then use a standalone PLC, if you require the flexibility that is normal in a CNC machine then use one of the devices I mentioned above.
Hood