creating a 3v d.c. supply

Discussion in 'The Projects Forum' started by matttiger22, Dec 14, 2014.

  1. matttiger22

    Thread Starter New Member

    Dec 7, 2014
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    Hi all,
    I am making a little winding railway that moves a cart up and down the slope automatically using a simple 12v d.c. relay logic circuit. the only problem I have is powering the 3v d.c. motor. I could wire a separate supply in the way of a battery to it but I would rather use the same 12v d.c supply from the mains. How would I get a voltage drop to power the motor? The motor speed will be controlled with a pot
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    527
    Use lm317.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Lm317t ,or a 3V regulator..
     
  4. Wendy

    Moderator

    Mar 24, 2008
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  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Where and how will the speed of the motor be controlled?
    It can not be controlled over the 12 Volts when you use a LM317 regulator.

    Bertus
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    You could use the LM317 but use a fixed resistor to limit the maximum voltage to 3V, and let the variable resistor control from 1.2 to 3V. Do the math for the resistances so you set this up right.
     
  7. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Won't thatLM317 get mighty hot dropping 9V? A switching regulator might be a better way to go. The 34063 is a bit old school but easy to wire up with lots and lots of support on the internet. One can be had from one of those cheap USB chargers. A simple mod and the OP has his 3 V. Only problem getting the right sensing resistor.
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    True enough, but OP is not likely to be able to build anything too complex. The LM317 will need a heatsink though.
     
  9. flat5

    Active Member

    Nov 13, 2008
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