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  1. #1
    Join Date
    Aug 2011
    Posts
    21

    cnc step/dir. cw/ccw

    Can anyone please tell me what is the difference between this step/dir and cw/ccw on a stepper motor driver?because I dont know how to connect to the cw/ccw . please help

  2. #2
    Join Date
    Mar 2007
    Posts
    2083
    Hi Deslee

    with step /dir

    pulses to the step input makes the motor turn

    the direction signal controls the direction (as expected)


    with cw/ccw

    pulses to the cw input turns the motor in one direction

    pulses to the ccw makes it turn in the other direction


    if you have the wrong control signals for a stepper driver

    its possible to convert them

    John
    Attached Thumbnails Attached Thumbnails clock - direction and clock up-clock dowm.jpg  

  3. #3
    Join Date
    Aug 2011
    Posts
    21
    thanks john 100 I used the stp/dir bob to control cw/ccw driver ,nowander it did not work . so, do you have any kind of this schematic bob ,so I can make my own. hope to hear you so . thanks

  4. #4
    Join Date
    Mar 2007
    Posts
    2083
    Hi Deslee ,

    since my last post ,

    I've looked at your other posts and had a look at the AD5410 manual

    the circuit below should help

    the AND gates made from part of the 7400 and 7406 IC's

    can provide more current than a 7408 AND gate to drive the opto isolators

    the 150 ohm resistor limits the LED current to a similar level to the "MF"

    inputs

    the step signal is switched to the CW or CCW depending on the

    logic level from the direction signal

    (note the NAND gate used to send the inverted direction signal to

    one half of the circuit)




    John
    Attached Thumbnails Attached Thumbnails AD5410 step -direction converter.jpg  

  5. #5
    Join Date
    Mar 2007
    Posts
    2083
    Hi Deslee ,

    I've just had a thought

    you could use a 74241 octal buffer

    only two of eight buffers are used

    John
    Attached Thumbnails Attached Thumbnails 74241 step-dir to cw - ccw converter.jpg  

  6. #6
    Join Date
    Aug 2011
    Posts
    21
    Hi John,
    does this mean i have to use 3 74241 to link it to my stp/dir bob?

    so,i can use 3 drivers.

    because i just have some basic electronics knowledge .thanks

  7. #7
    Join Date
    May 2007
    Posts
    781
    Where are your step/dir signals coming from?
    I believe EMC can be configured to generate cw/ccw directly.

  8. #8
    Join Date
    Mar 2007
    Posts
    2083
    Hi Deslee,

    yes you will need three 74241 IC's ( one for each axis)

    the unused parts can not be used because each of the two enable pins
    control 4 buffers

    John

  9. #9
    Join Date
    Aug 2011
    Posts
    21
    hello john
    the circuit you give me is not working
    I use it on kcam and mach3 no movement at all
    any circuit I can try ? please let me know.
    thanks.

    stp/dir signals coming from parallel port.

    what is EMC?

  10. #10
    Join Date
    Mar 2007
    Posts
    2083
    I've not used EMC

    but I understand its a LINUX version of the

    the Kcam and Mach3 type of software for windows


    have you used Kcam or Mach 3 to control another stepper

    motor driver before?


    if not try the step and direction test circuit from Geckodrive :--

    Support

    look in application notes-
    open the miscellaneous tab
    then open step and direction tester


    I've added led indicators to the 74241 circuit

    the direction signal should switch between the two led's

    the step signal should make one flash on or off


    john
    Attached Thumbnails Attached Thumbnails 74241 step-dir to cw - ccw converter+ leds.jpg  

  11. #11
    Join Date
    Aug 2011
    Posts
    21
    hi john

    I did used kcam for the l297/l298 drivers

    what do mean test circuit from geckodriver?

    can you draw the led circuit for me?

    thanks

  12. #12
    Join Date
    Mar 2007
    Posts
    2083
    Hi Deslee ,

    it looks like you made your last post while I was re-sizing the picture of

    the 74241 circuit with the two LED's added (one for CW and one for CCW)

    the picture was too big when uploaded first time


    the test circuit from Gacko was just incase you had problems
    with the control of the printer port and the 74241 adaptor circuit

    if you select in Kcam (or Mach 3) negative going pulses

    one led should be on
    the led will dim as you rapidly send pulses to turn the motor

    for positive going pulses
    the led will be off until , you send step pulses
    the faster the pulses the brighter the led


    you can test the 74241 circuit on its own ,with just a 5V supply connected

    you should have one led on

    connecting the direction input to 0V it should switch to the other led

    connecting the step input to 0V will switch off the led



    John
    Attached Thumbnails Attached Thumbnails StepDirectionTester.jpg   74241 step-dir to cw - ccw converter+ leds.jpg  

  13. #13
    Join Date
    Aug 2011
    Posts
    21

    Smile

    Hi john

    sorry for the late reply,my computer just attack by virus ,cant get online.

    Anyway, thank you so much for all the information you provided.

    The circuit you gave is working great , is just my paraller port cable make

    thing wrong .I bought another new one.

    Its working great .Thank you , Thank you.

  14. #14
    Join Date
    Mar 2007
    Posts
    2083
    Hi Deslee ,

    good to see its now working

    did you add the LED's to see what its doing ?

    the computer virus is a real pain

    John

  15. #15
    Join Date
    Aug 2011
    Posts
    21
    HI John

    Yes I did add the LEDS to the board .When switch on ,

    the led from the IC pin 7 stay on.
    when move forward and backward ,the two LEDS became on and off.
    Is good to have a LEDS on board ,made things more fun.

    And john ,I have another question that need your help .
    currently I am using the stepper driver board (L297-8)
    this board I build was follow from the book

    CNC ROBOTICS(Build Your Own Workshop Bot)
    by GEOFF WILLIAMS

    The book didnot mention a lot about the schematic,I was confuse ,
    it seems that the board L-297 pin 15 VREF it just connect to somewhere else.I dont understand,because I read the pminmo.com website,the driver they build ,the pin 15 VREF it got an adjustable resistor.
    so ,what I mean ,does its better have an adjustable resistor or if not? how it control the current to the motor.I also attach the schematic from the book.

    thank you
    Attached Thumbnails Attached Thumbnails L297.jpg  

  16. #16
    Join Date
    Jan 2010
    Posts
    2141
    Instead of using a potentiometer (adjustable resistor) to select the value for Vref, the schematic that you attached uses two resistors, labeled R5 and R6, as a fixed-value voltage divider circuit to get Vref.

    The ratio of the resistance values shown on the schematic gives you a Vref of approximately 1/6 of the board's input voltage (1/6 of the "circuit voltage" applied to pin 1 of the JP1 power connector).

    For more information about voltage dividers, see Voltage divider - Wikipedia, the free encyclopedia

  17. #17
    Join Date
    Mar 2007
    Posts
    2083
    Hi Deslee

    the V ref for the circuit you have built will be 0.9V ( 5V x R5/{R5+R6} = 5 X {2200 /12200 })



    this sets the current in the motor coils to 1.8A (Vref/ R1 = 0.9/0.5 )

    what do you need to set the motor current to ??

    circuits with a potentiometer to adjust the reference voltage makes it easy to set
    the current for the motor ,an advantage when your experimenting
    but with age potentiometers can become unreliable

    with R1 and R2 being 0.5 ohm the maximum reference voltage is 1 Volt
    as the total current limit for L298 IC is 4A ( 2A per coil)

    if you change R5 from 2k2 to 4k7 and R6 from 10k to 18k

    the reference voltage will be 5 x 4.7/22.7 = 1.03V , I = 1.03/.5 = 2.06A

    John

  18. #18
    Join Date
    Aug 2011
    Posts
    21
    Hi

    Doorknob ,John

    Both of you ,thank you so much .Now I know whats that all about.

    I finally understand what it mean. thanks a lot.

    deslee:banana:

  19. #19
    Join Date
    Nov 2005
    Posts
    19
    Hi, this discusion is very interesting for me, I am trying to drive stepper drivers with CW/CWW inputs. I am still in research for BOB, but i want to test my drivers. Can I ask electronic gurus to have a look at the attached shematic - my drivers are not optoisolated. Will this work?
    http://img249.imageshack.us/img249/7911/shemal.jpg



    Uploaded with ImageShack.us

  20. #20
    Join Date
    Mar 2007
    Posts
    2083
    Hi

    as the printerport can sink more current to 0v/gnd
    than source current from the +5v supply
    you may be better connecting the opto-isolator V+ terminals to +5v
    from the computer usb port
    and connecting the VF- terminal via the resistor to the printerport


    John

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