Need Help with 2-phase 4-lead-wire stepper motor Actuator

Discussion in 'The Projects Forum' started by george0039, Jan 14, 2013.

  1. george0039

    Thread Starter Active Member

    Oct 15, 2008
    126
    5
    Hello
    I need advice. I have a 2 phase 4 wire stepper motor actuator. The circuit that controls it has micro buttons, one for forward and another one for reverse. As long as you hold down the button the motor moves the actuator in that direction. I don`t want/know how to do anything with the chip that controls the motor.

    What I would like to know if it is possible to have a momentary push button so that all I have to do is puch the button in the direction I want the motor to drive the actuator and release the button then when the actuator comes to the End of it`s travel, it stops. Then when I momentarily push the other direction button, the motor starts and drives the actuator to the start position or end of travel and stops.

    Can those two functions be done and parts be of small size? Any pictures, diagrams etc. would be Greatly appreciated.

    Thanks for your Time and Help.

    George
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Do you have anything that signals when the "End of its travel" occurs? If not then you will need to add limit switches.

    Then you could use a relay connected as a latch (one for each direction), operated by its respective push button as shown here. The normally-closed limit switch is connected in place of the Reset Switch and thus unlatches the relay to stop the motor.
     
    Last edited: Jan 15, 2013
  3. george0039

    Thread Starter Active Member

    Oct 15, 2008
    126
    5
    Hello again

    Thanks for the Fast reply BUT I failed to include that this was to be used in a R.C boat and it`s power source would be either; 6v min, 7.2v, 7.4v, 12v max.

    The Stepper motor with linear actuator and control board has Nothing to detect end travel. If you continue to hold the micro direction button the motor will not stop turning and driving the actuator.

    So to repeat. I would like to have something added so that I could momentarily push the forward button, motor drives the actuator till the end of travel then stops. When the reverse micro button is momentarily pushed the motor drives the actuator back to the full start position and stops.

    Can this been done? Keeping in mind, simple parts added would be Great!

    Thanks Again

    George
     
  4. crutschow

    Expert

    Mar 14, 2008
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    And so I repeat, you will need to add some type of limit (micro) switch to detect the end of travel. :rolleyes: Only you would know how to physically place those switches.
     
  5. george0039

    Thread Starter Active Member

    Oct 15, 2008
    126
    5
    Hello Mr. Crutschow

    Thanks for your help with this. I have hopefully?, included a link to what I have bought and am waiting for; http://www.ebay.ca/itm/221128118063?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

    Could you please have a look at it and PLEASE try to explain to me the simplest way I can get my stepper motor unit to do what I need as follows.

    1. When I push the Fwd micro button, I want it to be just a momentary push and not have to hold the fwd micro button.

    2. When motor goes to the end of it`s travel, it stops there.

    3. When I push the Rev. micro button, I want that to be a momentary push and not hold it.

    4. When the motor drives the mech to the start position, I want the motor to stop.

    I understand the use of limit/position switches and I have some small micro switches that I plan to use here. I just a Simple Small circuit for this as space is an issue. Also the main battery power would be either; 6v, 7.2,v 7.4v, 12v, not decided yet, MOST likely 6v or 12v gel cell.

    Please let me know with a circuit as the site you added in your reply had a few and even offered a finished relay circuit for sale. I don`t know which one OR the wiring to do it.

    Thanks Again for the Help.

    George
     
  6. crutschow

    Expert

    Mar 14, 2008
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    You would use two of the second circuits in the reference, with the limit switches replacing the corresponding reset switches. One circuit is used for one direction and the other used for the opposite direction.
     
  7. John P

    AAC Fanatic!

    Oct 14, 2008
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    I think you can do this with an external flipflop circuit like a 74HC74. You would take an output of the flipflop, pin 6 or 8, and connect it to the point on the circuit board where the pushbutton connects to the processor. Then the 74HC74 would be the "button" that drives the processor pin. Then drive the "set" and "reset" inputs of the 74HC74 with pushbuttons to Gnd and pullups (3.3K?) to Vcc. When you push "set", you'd be starting the motor and when you push "reset" you'd be stopping it, so you use those as the "run" and "hit limit" switches for one direction of travel. The 74HC74 has dual flipflops, so you have one each there for forward and reverse motion.

    I suggest connecting the "clock" inputs of the 74HC74 to a pullup to Vcc and a capacitor to Gnd, and both D inputs to Gnd; that should create a highgoing input on the clock an instant after power goes on, which would reset the flipflops to ensure that the unit starts off with the motor stopped.

    If you use this idea, you should either remove the pushbuttons from the board, or make the connections from the flipflop through resistors. If this isn't done, you risk having a conflict between the existing button and the 74HC74 output.

    What happens if you push both buttons? Nothing catastrophic I hope.
     
  8. george0039

    Thread Starter Active Member

    Oct 15, 2008
    126
    5
    Hey John P

    Can you show me a circuit schematic of what you said above and doing what I listed in the above posting? I have limit switches BUT I have to try to keep this as small, physically as possible, because of space issues.

    Thanks for the help.

    George
     
  9. crutschow

    Expert

    Mar 14, 2008
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    So you don't have enough room for two relays?
     
  10. John P

    AAC Fanatic!

    Oct 14, 2008
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    OK, here you are. This is untested, but it's what I would start with. The power supply for U1 isn't shown but definitely needs to be there (on pins 14 and 7) and it needs a capacitor across it near U1. Looking at the drawing now, I'd make C1 a lot bigger, say 100uF, with the negative side to Gnd.

    [​IMG]

    The idea is that there's a flipflop for each direction, which gets "set" when you push S1 or S3, and "cleared" when the limit of travel is hit, which presses S2 or S4. If you try to hit the "go" button at the same time as the limit, the limit wins, as it should. But as I said before, I don't know what that processor does if you try to go forward and back simultaneously.

    Resistors R6 and R7 are there in case the existing pushbutton conflicts with the output of U1. If you're sure those controls will never be used or if you take them off the board, you could skip those two resistors.
     
  11. george0039

    Thread Starter Active Member

    Oct 15, 2008
    126
    5
    Hello Crutschow

    In reply to your post 9. I have a small 1/350 scale aircraft carrier that this is going to be used in for the hanger elevators. From the picture in the other site, the relay with it`s circuit board looks bulky and the cavity space inside the carrier is ver tight.

    If there is another way to do this Simply with as little circuitry then I`m all for it.

    If you have any suggestions please let me know.

    Thanks Again for the help.

    George
     
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