HELP PLEASE!

Discussion in 'The Projects Forum' started by Petergombasek92, Dec 3, 2014.

  1. Petergombasek92

    Thread Starter New Member

    Dec 3, 2014
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    I'm currently undertaking a D.I.Y project of making a magnetic stirrer capable of stirring liquid quantities in excess of 20L +
    By trade km a plumber and electrical doesn't scare me, not at all its the fact that I'm clueless within regards to component capability, and I don't even know were to start when trying to study a wiring diagram or circuit drawings..... I thought I could work it out but im sick of buying replacement components as I keep blowing then over and over and over.....

    My supply list is as followed,
    -Standard high power DC motor @ 9700RPM

    - my mains power is 240V AC, Electric motor is DC.... Ive been trying to make it work with something like a laptop charger... to achieve AC TO DC
    Specs:
    Input: 240V-50Hz 15W
    Output: 15V d.c.500mA

    -potentiometer (Motor speed controller)

    CAN SOMEONE PLEASE SHOW ME HOW TO WIRE THIS THING !
     
  2. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    526
    That charger cant supply 1A needed for motor to work at full power and potentiometer cant handle that kind of power.Cheap pots are under 0.5W.
    You should use PWM.
     
  3. Petergombasek92

    Thread Starter New Member

    Dec 3, 2014
    6
    0
    Can you possibly guide me in the right direction?
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Do you have a spec for the motor?
    Voltage at max RPM..
    Current draw at stall (max current draw).

    Desired RPM when stirring your flask.

    Also, why magnetic and not an overhead stirrer?
    Large flasks are not normally stirred magnetically because the stir bars would be too long and fat for that much torque and do not have enough magnetic strength. Therefore, they keep spinning off-axis (inefficient mixing).
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Not really surprising noting the specs you have supplied so far, as already mentioned the complete specifications of the motor are needed.
    240vac 50Hz, I assume you could be in UK?
    Max.
     
  6. Petergombasek92

    Thread Starter New Member

    Dec 3, 2014
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    I live in Australia, full motor specs are quoted with the link I pasted the link shows these specs as followed bellow;

    Operating Range (V) 6-18


    No load
    • Voltage (V): 12
    • Speed (rpm) 9700
    • Current (A) 1.3

    At Stall
    • Torque (kg.cm) 6.0
    • Current (A) 57

    At Max Efficiency
    • Efficiency (%) 73
    • Power (W) 52
    • Speed (rpm) 8490
    • Torque (kg.cm) .60
    • Current (A) 6.0

    Dimensions
    • Diameter (mm) 42
    • Total Length (mm) 85
    • Shaft Length (mm) 19
    • Shaft Diameter (mm) 5.0
    • Mounting Thread M4
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Ebay $5.00, 251539147533 just one of many.
    You don't really need a regulated supply for DC motor control.
    Max.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Are you sure of the torque demands for the motor?
    It appears without some kind of gearing you may have a torque miss match?
    Do you need 9700rpm?
    Max.
     
  10. wayneh

    Expert

    Sep 9, 2010
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    You do know that large magnetic stir plates are commercially available? I used one for stirring 5-gllon pails and 20L glass carboys.
     
  11. Petergombasek92

    Thread Starter New Member

    Dec 3, 2014
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    Yea I know but I pride my self in my own sense of self satisfaction when i do something myself rather then just pick it up off a shelf :) :) :)
     
  12. wayneh

    Expert

    Sep 9, 2010
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    Me too, but I choose my battles carefully. I build as a last resort, after first ruling out buying, followed by hacking something similar.

    9700 rpm sounds WAY too high. I would guess a couple hundred rpm is as fast as a magnetic stir bar can go.

    How are you going to spin the magnetic field, to drive the stir bar?
     
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