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DC motors -- speed control question

  1. Nov 3, 2014 #1
    hi there,

    I have 3 dc motors (12v-5 ampere)that are connected each with a speed reducer gearbox, actually I want to control these motors with a JOY-STICK switch just controlling there movements in fixed speed, should I use a pwm circuit to drive them or a simple 3-axes joy-stick is enough?
    if yes, where can I find a joy-stick that meets my motors requirements?

    thanks in advance
     
  2. jcsd
  3. Nov 3, 2014 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF.

    For speed control on the DC motors, you need to use PWM circuits. How are you planning on controlling 3 motors with a 2-axis joystick?
     
  4. Nov 3, 2014 #3

    billy_joule

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    Science Advisor

    Seeing as you want fixed speed you may not need PWM - simple on-off switch control will give you fixed speed, you can control that speed with by altering the supply voltage. It will probably cost a lot less than 3 x PWM.

    The problem is that you may not be able to find a 3 axis Joystick with simple switches, they all seem to have pots like so:

    http://www.superdroidrobots.com/shop/item.aspx/analog-3-axis-joystick/1263/

    Which could control 3 PWM's or relays but not motors directly


    The arcade style 2 axis joysticks have 4 micro switches (8 positions in total) which could control four 10A loads directly.

    http://www.arcadomaniashop.com/Arcade-Joystick-Japan/en


    Ultimately it depends on how you want the motors to function relative to the joysticks positions...
     
  5. Nov 3, 2014 #4
    what if I found a low power joy stick and connected it to the motors through relays?
    what do you think in this case? isn't better?
    if this scenario is accepted, does it affect the motor with any side effect?
    can I use a resettable fuse as an example to protect my motors?
     
  6. Nov 4, 2014 #5

    billy_joule

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    Science Advisor

    Define 'better'.
    Using relays complicates things, whether this is necessary or even beneficial cannot be known with the information you've given.

    Relays are just regular switches as far your motors are concerned so will have the same effect as any other switch would.
    Protect your motors from what exactly?
     
  7. Nov 4, 2014 #6
    protecting the motor from any high current may consume and hence damaging the gear as an example if the load differs or the motor jammed
     
  8. May 18, 2015 #7
    Woodmizer sawmills use a 12v electronic control module with a 1k pot hooked to it. The output of the ECM feeds the gates of 4 IRFZ44N Mosfet transistors connected in parallel to power a 3/4 hp 12 volt DC motor from 0 to full speed with current up to 50 amps. The variable speed motor powers the carriage that saws the logs. You may be able to adapt this to higher voltage dc motors up to 48 volts. The Mosfets will go up to 55 volts. Power the ECM with 12 volts.
     
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