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Coil turns number

  1. Jan 16, 2011 #1

    I am making an electromotor. How many turns of 0.4mm/26 Gauge wire should I make so as to run the motor at 9 Volts? (I`ll count the needed wire length assuming that 1 turn of wire = 8.5cm.)

    Thank`s in advance & please let me know if you need more info... :smile:
  2. jcsd
  3. Jan 16, 2011 #2


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    Impossible to know without information on dimensions, field strength, size and location of permanent magnets, drawings of the iron poles, etc. If you are building a simple demo motor (using a steel screw for a rotor, and refrigerator magnets) then a couple of hundred turns on each pole should suffice.
  4. Jan 16, 2011 #3
    Hmm, the site I found the scheme at suggested 50 turns for 6 volts.
  5. Jan 16, 2011 #4
    Since ur turn length is 8.5cm, the core for the winding is 26mm or approx 1 inch I suppose.
    And as u r talking of 9 volt, I assume u are talking of a DC motor.. As suggested y Marcus, please provide more information.. pertaining the dimensions u r likely to build the motor in, the Permanent Magnet dimensions and type etc...

    if u do not wish to share the information.. this link may still be useful to u to judge the winding ratio in comparison to the suggested V motor in the guide that u are following. BUt wierd that the guide did only tell u how and not 'why'.
    Last edited: Jan 16, 2011
  6. Jan 16, 2011 #5
    This link is in german.. but I guess Google translator or any other translating medium may help you better understand it..
    http://www.powercroco.de/draht_magnet.html [Broken]
    Last edited by a moderator: May 5, 2017
  7. Jan 17, 2011 #6
    The link you provided in the last post *might* do the job...

    After entering the essential parameters, it counted that my coil has resistance of 0.187 µΩ. (length - 2.1m, wire diameter - 0.5mm).

    What now? My physics knowledge is not yet perfect, so some help would not do any damage.
  8. Jan 17, 2011 #7
    Would you be able to share more information. It would help me to come up with a sensible suggestion or answer to your query.
  9. Jan 17, 2011 #8
    Sure, just let me know what kind of info you need...

    Now I am going offline. Just say what you need and tomorrow I`ll post the info.
  10. Jan 17, 2011 #9
    i dont even know what kind of motor u are trying to build, just from the discussions I understand that you may be building a simple 9VDC Brushed Dc motor.
    Is this what u are trying to build:: http://www.instructables.com/id/The-Simple-DC-Motor/
    or u could try this
    these will help you better understand the motor concept.
    if you are looking to build a more sophisticated or practically applicable motor, let me know the specifics of what u want the motor to do using a potential of 9V.
  11. Jan 18, 2011 #10
    That`s my mistake. I didn`t include such info.

    Initially I was following these instructions:

    http://www.howard.k12.md.us/res/MakingStuff/motor.html" [Broken]

    However, when everything was finished, the motor wouldn`t start. I wasn`t sure what was the problem, so now I am replacing the permanent magnet with an electromagnet.

    Here is a simple scheme of the electromagnet:


    Soon I`ll post a pic of it as well.

    All of my questions were related to the above electromagnet.
    Last edited by a moderator: May 5, 2017
  12. Jan 19, 2011 #11
    Bump... :)
  13. Jan 28, 2011 #12
    Hi, sorry couldnt get back to you... was entangled with work the last 10 days... will get back to you this evening(another 10 hrs...)
  14. Jan 28, 2011 #13
    It`s OK. Now it`s time to show my progress...I managed to get it working by winding the coil in the opposite direction (I used a permanent magnet).

    However, when I connect the stator & rotor electomagnets in parallel circuit, I get ~1V @ the both electomagnets. How can I increase the voltage? (I am using 4.5V battery)...
  15. Jan 28, 2011 #14
    @ that time what voltage do you get at the battery source, if even that is like say, 1V. then it means that the current requirement of the ckt causes the voltage to drop.
    What is the current value recommended for the ckt, if the recommended value is less then u can try putting a small value resistor (after calculation) in series at the battery end of the ckt.
    Or you can put a few 4.5 V battery groups in parallel and increase the effective current of the ckt.

    But before that do check the terminal voltage across the battery while it is a part of the closed ckt, and post the value. The battery if measured outside the circuit may show a voltage closer to 4.5V.
  16. Jan 28, 2011 #15
    I don't have any info about the recommended current, but I think the battery can't deliver the required current (~5.5 Amps).

    Currently I am unable to measure the voltage @ the battery terminals while a part of the closed circuit, but when it's not a part of closed circuit it shows ~4.48V which is OK.

    Perhaps adding more volts can increase the current in the circuit, but I think that adding a resistor in series should result in less Amps required (i.e. a small DC12V computer fan has resistance of 100 Ohms and the current flowing through it is as little as ~120mA.

    If you have any suggestions please let me know...
  17. Jan 29, 2011 #16
    include a 10ohm 2Wpower resister or as you say a 1/2 watt 50 ohm resistor in series. this will limit the current to about .5 or .1A.
    but also the voltage on the coil will be affected.
    You should be able to measure the voltage of the battery while it is the ckt, same as the coil voltage, it will also show approx. 1 V.
    so try placing batteries in parallel...
    Your inductive coils resistance is not sufficient, you should probably double your number of turns, or use a higher gauge wire and more number of turns...h
  18. Jan 29, 2011 #17
  19. Jan 30, 2011 #18
    Hmm, my motor spins great when using one permanent magnet (stator) and electomagnet (rotor).

    But, we are discussing something else - the voltage drop. I am going to measure the voltage of the battery when in a circuit as well as connect a resistor in series.
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