DC motor stops working (too much load?)

Discussion in 'General Electronics Chat' started by alepe, Nov 13, 2014.

  1. alepe

    Thread Starter New Member

    Nov 13, 2014
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    hello, i'm starting to have some fun with electronics with my kids.
    we build a small light aeroplane with wheels and put a 12v dc motor on it with a propeller.
    Hope was to see it moving ahead not yet flying, but the motor starts turning nicely and after about 1 seconds
    stops working. If i remove the propeller it works perfectly, if i put it back, it stops again.

    I tested the same circuit with a 1,5 v battery and propeller, and then the motor works slowly but nicely,
    what's going on?

    thanks
    alex
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi,
    Post details of the 12V battery, depending upon the type ie: current rating it may not be able to supply the required motor current to drive the prop.

    E
    A quick check would be to measure the 12V battery with and without the prop.
     
  3. alepe

    Thread Starter New Member

    Nov 13, 2014
    4
    0
    actually it was a 9 V battery, standard duracell from any shop.... i tried also to put two of them in series to get 18V, and got same result.
    What do you mean by current rating? i guess there is nothing written on the battery, but shall i measure current flow with amperometer ?
    Also the DC motor was bought over internet and came without any data sheet, only specification was 12 volts.

    if the current is not enough, shouldn't the prop just spin slowly, i mean it should not give enough push to move the aeroplane, but still moving the prop as a little fan ?
    why 1,5v works like that but 9v stops it?
    thanks!
     
  4. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi,
    Is the 9V battery a PP3 type, rectangular approx about 1 inch * 2 inch,? If so I would say it cannot produce sufficient current to drive a medium/ heavy current motor..

    A 1.5V AA size battery can supply 1 to 2 Amps for a short period.

    Measure the current drawn by the motor from the 1.5V battery, this will give you a rough guide to the current required at 12V
    Use Ohms law to get an approx value for the motor resistance...
    E
     
  5. alepe

    Thread Starter New Member

    Nov 13, 2014
    4
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    ok thanks, I'll do that.
    this actually makes a lot of sense. any suggestions where to find a proper battery?
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,763
    1,099
    We don't know where you live, but any reputable electronics store/supplier would have one.
     
  7. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    You could get two battery holders for say 4 * 1.5V [ AA] so 6V each holder.
    Depending on the capacity of the planes fuselage you may get them to fit inside.
     
  8. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    526
    If that's brushless motor used for RC planes than he is rated in Kvs.They are normally run with 3,7V.
     
    Last edited: Nov 13, 2014
  9. alepe

    Thread Starter New Member

    Nov 13, 2014
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    0
    thanks everybody for helping!
    i live in Helsinki Finland, so an online store would be best.

    I was thinking about the 2 x four batteries holder solution as well, i was just thinking about the extra weight,
    but i'll try and let you know !

    it was a general purpose dc motor, cheap, just for testing with kids what we can do

    alex
     
  10. ISB123

    Well-Known Member

    May 21, 2014
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    That kind of motor can't power planes since it doesn't have enough RPM,you can build a car or some kind of tracked vehicle.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,495
    2,364
    Post a pic of the motor if possible, if this is a brushed motor, you can spin it by means of a drill chuck etc and read the DC generated, if it is supposed to be a 12vdc motor then see if you can produce 12v, this voltage will be proportional to the actual rpm produced by the chuck.
    Max.
     
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