Convert Step/Dir to +/- 10V

[SkyG]

Hello -

I have some Baldor TSD drives that take +/- 10V control, but I would like to use a CNC4PC Breakout board. A friend of mine said that someone makes some small converter cards that will take step/dir and output +/- 10V. Does that ring a bell for anyone?

-Sky

[jjobezo]

You may look at this one.

http://diycnc.co.uk/html/spindle_2.html

[H.O]

The one linked to on the DIYCNC site will only work for open loop speed control ie. a spindle motor. It won't work for positioning the machines axis if that's what you want.

Do a search for the YAPSC:10V - it will do what you want. You could also use the JRKerr PIC-SERVO SC with an added output filter (shown in the manual). Or you can go to an external motion controler like the DSPMC or Kflop+KAnalog (if using Mach3).

/Henrik.

[jjobezo]

per Baldor's website.

TSD
DC Servo Drive


DC Servo Drive
The TSD from Baldor is a DC servo drive providing control for DC servo motors. Operating directly from 115 VAC it will provide up to 5 amps continuous (peak = 2x) and will power servos requiring 50 or 100 volt bus. The TSD is a totally enclosed, stand alone unit.

A simplified packaging concept will allow one to take the TSD from its shipping carton and have it operational within 10 minutes. Just plug it in and it’s ready to go.

The TSD easily interfaces with today’s motion controllers, and uses the industry standard +/- 10 Vdc input command, along with tachometer feedback for velocity loop operation or it may be set up for torque/current mode of operation. This DC servo control is fully protected and includes protection against: over/under voltage, over temperature, excess/surge current, short circuit protection, and loss of logic voltage.

[H.O]

Yes, but if you are going to use an analog input servo amplifer as part of a positioning system you have to close the position loop somewhere. The F/V converter board at DIYCNC does not do that.

Normally you have an encoder on the motor, it feeds position information back to the controller which calculates how much torque is needed from the motor to cancel out any discrepancy between target position and actual position. The controller then outputs an analog voltage (+/-10V) indicating the required torque.

With open loop control software, like Mach3, that uses step- and direction signals there is no position loop in the control software. It does not know where the motor actually is and relies on external hardware to see to it that the motor is where it's told to be.

Simply converting the frequency of the step-pulses to an analog voltage won't work for positioning as there is no control loop. It won't notice if the motor slows down, it won't notice if it stalls, it won't notice if it is moved when it's supposed to be stationary etc etc. (Though the drive has tach feedback so it's not completely blind, it still won't work for position though).

The hardware device needs to take step- and direction signals from the controller (ie. Mach3) AND encoder feedback from the motor and have an internal control loop (PID usually) that continously "tells" the drive how much torque it wants from the motor to keep it where it's supposed to be.

Now, if this would be for say a spindle drive where only the speed (and not position) of the motor needs to be controlled then a simple F/V converter would work nicely.

If you want more info on some of the ways that you can interface analog control servo amplifiers/drives to Mach3 I have a page here.

/Henrik.

[jjobezo]

Originally Posted by SkyG Hello - I have some Baldor TSD drives that take +/- 10V control, but I would like to use a CNC4PC Breakout board. A friend of mine said that someone makes some small converter cards that will take step/dir and output +/- 10V. Does that ring a bell for anyone? -Sky

He never mentions anything about positioning.

[jalessi]

The CNC4PC "C6 variable speed control board" may be what you are looking for.

http://www.cnc4pc.com/Store/osc/prod...products_id=58

[H.O]

He never mentions anything about positioning.

You're right, which is why I in my first post wrote:

It won't work for positioning the machines axis if that's what you want.

The reason I personally think it's for positioning is the fact the he DID say he wants +/-10V. (Which neither the Spindle2 board from DIYCNC or the C6 board from CNC4PC will do by the way, they only do 0-10 and a direction toggle relay).

But again, if this is for an open loop (position wise) drive where only the speed (and not position) of the motor needs to be controlled then a simple F/V converter will work nicely.

/Henrik.

[SkyG]

Hey guys - Indeed, I do want to use it for positioning, so it looks like what I'm looking for might not exist.

[groov]

SkyG,

What you are looking for is a level shifter that can take the digital signal (step/dir) from their present digital voltage levels and shift them to +10V/-10V.
There are several ways to accomplish this task, you can use comparators with +/- 10V outputs or if the signal is not switching fast, you can use an RS232 interface circuit. Of course there are some other ways but the first two should accomplish what you desire. Keep in mind the polarity of the signal.

Hope it helps.
groov

[pfred2]

An open collector buffer and pull up resistor will do it too.

[H.O]

Come on now guys,
He has step- and direction signals from a digital positioning controller (Mach3 perhaps) and wants to run a servo amplifier that takes an analog +/-10V command signal. A levelshifter will not do it, nor will a F/V converter for reasons outlined in previous posts.

SkyG,
Did you not read the replies you got? There ARE solutions and products available, please re-read post 3 in the thread and or look here

/Henrik.