Question 2 DC Motors

Discussion in 'General Electronics Chat' started by ronandavid, Jul 12, 2016.

  1. ronandavid

    Thread Starter New Member

    Jul 12, 2016
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    hi and im new in this forum sorry if i posted it in the wrong section , but my question is this is it possible to control 2 dc motors using 4 microswitch with common , no , nc contact ( joystick mechanism ) , the forward switch will control the 2 motors forward and the reverse switch will control the 2 motors reverse , and the left switch will only control 1 motor which is the right motor , and the right switch will control the other motor which is the left motor ( just like electric wheelchair ) btw 24v supply , your help is much appreciated thanks. :)
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    The forward and reverse is easy, you wire the motors in parallel so they both do the same thing according to the switch selected.
    The other two actions, I am not sure about, if each motor has some additional individual controls, then yes, wire individual control to individual switch.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Do you mean that the joystick has four positions, i.e. forward,reverse,left,right, from the sound of your required directions this is what you may need to get wheel chair directions, using left-right for turning?
    Max.
     
  4. ronandavid

    Thread Starter New Member

    Jul 12, 2016
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    yes thats what i mean in my question i dont know if that is even possible :(. do you have any ideas on how to make that connection work ?
     
  5. ronandavid

    Thread Starter New Member

    Jul 12, 2016
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    the problem is that the dc motors only having 2 wires and no control in it.
     
  6. MaxHeadRoom

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    Jul 18, 2013
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    You need a 4 position joy stick controller, there are commercial ones used for machine control, switch sections are added to each as needed.
    Search ebay four (4) position joy stick
    Max.
     
  7. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Ah, ok, yes, that is pretty standard for dc motors. I am guessing to go forward they use + voltage, and to reverse direction they reverse the voltage polarity.

    As far as left and right switches, you will need some additional circuitry to control individual motors.
     
  8. ronandavid

    Thread Starter New Member

    Jul 12, 2016
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    thank you so much !
     
  9. ronandavid

    Thread Starter New Member

    Jul 12, 2016
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    thnx for the info ! :)
     
  10. Santhakumar

    Member

    Mar 17, 2015
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    I Guess you can try using Diodes..
    Did you try to have diodes in your circuit.
    Could you give joystick circuit..if available (to know how the switch connections are).
     
  11. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Untitled.png
     
  12. MaxHeadRoom

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    Jul 18, 2013
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    If you use discrete switches you should use interlock contacts on each relay to avoid inadvertent operation of two switches, with a couple of 2 posn joysticks you have automatic interlock.
    Max.
     
  13. MaxHeadRoom

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    Jul 18, 2013
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    That method does not appear to allow left fwd & rev and Right fwd & rev on their own which you would need to simulate wheel chair use.
    Max..
     
  14. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    No, but it meets the TS's specification and the addition of just two more diodes will allow turning on the spot.
     
  15. camerart

    Active Member

    Feb 25, 2013
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    Hi R,
    If you only want the wheelchair to be full speed in all directions, then relays will do this, but it seems to me that you should look at H-bridge circuits and PWM for speed control.
    Camerart.
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Wouldn't you also need simultaneous RH & LH but in opposite directions to simulate on the spot turning?
    Max.
     
  17. Tonyr1084

    Active Member

    Sep 24, 2015
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    While I like Blocco's approach, one thing I noted; that when driving forward (for instance, the left wheel only for a right turn) there is little more than dynamic braking to hold the right wheel steady. Without dynamic braking it's possible inertia may keep the wheel chair going forward even though being driven by only one motor.

    If it's feasible (outside the parameters you've set up) you could use two joy sticks, one for the left wheel and one for the right. Move both forward and the chair (if it's a chair) goes forward. Move only the left forward and the chair will tend to turn to the right. Move the left forward and the right backward and the chair pivots in place. Move both back and the chair moves backwards.

    Another excellent point is made by Camerart. All on or all off. Not very comfortable. And if you attempt to modulate speed by moving the switch(es) forward half the time then the other half of the time the motors will (if permanent magnets) will tend to apply the brakes.

    What you ask for is possible. But so far all I've seen is some nice solutions but not so practical. Someone mentioned looking into how wheelchairs are powered. My guess is that it may be done not so much by switches as much as it may be more so done by a micro controller.

    On that thought, you'd need a forward / reverse joy stick with variable degree input. Meaning if you push the stick 50% forward the chair will move forward at 50% power (or speed). Neutral (or at the zero position) you may not wish to apply dynamic braking. You may wish to use revers (thrust so to say) to slow or stop the chair. All this works well enough on flat ground. But what happens if you're on an incline? Coasting (or rolling away) can occur.

    I worked with a guy who always found problems with the solutions. I hate to sound like that guy. So my intent is to highlight obstacles that you'll need to consider and overcome. Somewhere out there is a solution.

    Good luck.
     
  18. MaxHeadRoom

    Expert

    Jul 18, 2013
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    IMO if true wheelchair style of control is needed, it requires at Least 8 modes of operation and does not include speed control, which unless very slow motion, may be needed.
    Both FWD
    Both REV
    Left only FWD
    Left only REV
    Right only FWD
    Right only REV
    Left FWD with Right REV
    Right FWD with Left REV.
    Max.
     
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