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  1. #1
    Join Date
    Oct 2005
    Posts
    13

    Convert Step/Dir to +/- 10V

    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

  2. #2
    Join Date
    Jan 2009
    Posts
    57

    possible option

    You may look at this one.

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

  3. #3
    Join Date
    Jul 2007
    Posts
    887
    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.

  4. #4
    Join Date
    Jan 2009
    Posts
    57

    Torgue,Velocity

    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.

  5. #5
    Join Date
    Jul 2007
    Posts
    887
    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.

  6. #6
    Join Date
    Jan 2009
    Posts
    57
    Quote Originally Posted by SkyG View Post
    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.

  7. #7
    Join Date
    Feb 2007
    Posts
    4553

    Post

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

    http://www.cnc4pc.com/Store/osc/prod...products_id=58
    Patience and perseverance have a magical effect before which difficulties disappear and obstacles vanish.

  8. #8
    Join Date
    Jul 2007
    Posts
    887
    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.

  9. #9
    Join Date
    Oct 2005
    Posts
    13
    Hey guys - Indeed, I do want to use it for positioning, so it looks like what I'm looking for might not exist.

  10. #10
    Join Date
    Sep 2006
    Posts
    58
    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

  11. #11
    Join Date
    Nov 2009
    Posts
    113
    An open collector buffer and pull up resistor will do it too.

  12. #12
    Join Date
    Jul 2007
    Posts
    887
    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.

  13. #13
    Join Date
    Sep 2006
    Posts
    58
    Yes indeed...after reviewing the Baldor specs and taking the time in reading the rest of the messages, HO is correct in assessing that a simple level shifter will not do the trick in this case. The TSD requires an analog input signal, differential or single ended, where the strength of the signal (amplitude) is directly proportional to the performance (speed, torque, etc) of the drive, if I interpreted correctly.

    groov

  14. #14
    Join Date
    Jan 2009
    Posts
    237
    US digital products might be a good reference.

    The attached pic is just one of the many converters they produce.

    Here is a link

    http://usdigital.com/products/interf...nverters/epot/
    Attached Thumbnails Attached Thumbnails epot2_0.jpg  

  15. #15
    Join Date
    Jan 2006
    Posts
    738
    I suppose one could build their own, although it would not be a simple circuit if using discrete components. Some sort of up/down counter that would be counted up or down by both a step and direction input and an encoder input. One step up would increase the count by 1 and the encoder feedback from the axis moving in the correct direction would decrease the count by 1. The count output could be compared against a value 1/2 of the full count and the comparison output used to control the +/- 10 V. Either a comparitor like the 74HC682 with the outputs decoded to control an integrator to generate the +/- 10 V, or a full ALU that would give you the difference in binary which could be fed to a D/A converter for your +/- 10 V output.

    A simpler implementation could be to use a programable microcontroller chip (maybe one that has an analog out) to do the counting and comparing.

    Steve

  16. #16
    Join Date
    Jul 2007
    Posts
    887
    That will give you a "regulator" with a proportional term only which most likely won't give you satisfactory performance.

    What you need is a PID regulator acting on the difference between the two "counts". This is exactly what the YAPSC:10V and the other products mentioned earlier does.

    You could use the "discrete" count and compare method, run its digital output thru a R2R network and then into an analog PID regulator. That is basically how the G320 from Geckodrive works. It has two 8-bit up/down counters which outputs goes to an 8bit adder, the output of the adder goes to a D/A converter which feeds the PID regulator.

  17. #17
    Join Date
    Dec 2013
    Posts
    28
    Seems to be a tough topic. I would think that someone would develop a reasonable interface to make the step dir to analog with closed loop, sure seems to be alot of interest in it. I have used the Gecko 320X and it does the job but not heavy enough for large machines that get used alot. The old style servo drives don't accept encoder feedback it go to the controller before the drive so it would have to be capable of step/dir in +/-10V out and quadrature encoder feed back with PID tunning
    and be resonably priced.

    Steve

  18. #18
    Join Date
    Feb 2012
    Posts
    149
    I use Galil motion controller for the system you describe. They are not cheap at retail but you can usually find good deals on eBay

    Sent from my XT1056 using Tapatalk

  19. #19
    Join Date
    Sep 2010
    Posts
    1765
    Quote Originally Posted by Machinehead57 View Post
    Seems to be a tough topic. I would think that someone would develop a reasonable interface to make the step dir to analog with closed loop, sure seems to be alot of interest in it. I have used the Gecko 320X and it does the job but not heavy enough for large machines that get used alot. The old style servo drives don't accept encoder feedback it go to the controller before the drive so it would have to be capable of step/dir in +/-10V out and quadrature encoder feed back with PID tunning
    and be resonably priced.

    Steve
    please define "reasonable price," voltage, & current required. we, like others, sell such devices but cannot guess what 'reasonable price" is.

    i would not consider a 'converter" but a drive that simply accepts step/dir input.

  20. #20
    Join Date
    Jul 2007
    Posts
    159

    Re: Convert Step/Dir to +/- 10V

    Actually these step/direction to analog converters do exists and work really well. The trick is the interface / converter between the the step and direction controller and the analog drive needs to receive an encoder input for positioning, this can be done by adding a simple encoder like the AMT102 to either the servo motor shaft or the actual ball screw. Then the required positioning loop is satisfied. This has been done many times. See eg here: https://www.audiohms.com/en/cnc-elec...cs-100-a-v3-en

    Viper drive also have one.

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