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  • Author Author: jw0752
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Unusual Way to Wire a small DC Motor

jw0752

Despite 60 years of playing with electronics this is the first time I have seen a DC motor wired in this fashion.  At first I did not expect it to work on DC current but to my surprise it took off and ran perfectly. Furthermore it did not matter if the polarity was forward or reversed. The motor continued to spin happily along. Just for the fun I also applied an AC current and once again the motor continued to whirl away. Here are some pictures of the motor wiring:

 

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Just to clarify how the motor is wired I also produced this small schematic:

 

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On first appearances I assumed the motor would start to turn and then stop when the small tantalum capacitor became charged. I did not initially understand why this did not happen. I am hoping some of my friends on the Forum with more experience and knowledge will confirm my speculation that the counter EMF in the motor actually discharges the capacitor allowing it to accept a second charge and continue to maintain the magnetic fields that spin the motor. I suspect that the low ESR of the Tantalum caps makes their charge and discharge rapid enough to facilitate this process. I do not know why the designer of the piece of equipment where this small cooling fan was used chose to use this particular circuit. It was something new to me and it caught my attention. Now I just want to understand it.

 

John

Parents

  • Very interesting design.

     

    The use of the diodes and capacitors is ingenious, simple, and very cost effective.

     

    The three components, don't forget the motor coil, all work in harmony regardless of AC or DC input.

     

    Each part creates a simple circuit to support motor operation based upon the exchange of current between each component.

     

    In some ways it is like a resonant circuit with the LC components with the two diodes providing the energy from the drive voltage in either direction.

     

    It should work fine with low current and low load conditions.

     

    DAB

Comment

  • Very interesting design.

     

    The use of the diodes and capacitors is ingenious, simple, and very cost effective.

     

    The three components, don't forget the motor coil, all work in harmony regardless of AC or DC input.

     

    Each part creates a simple circuit to support motor operation based upon the exchange of current between each component.

     

    In some ways it is like a resonant circuit with the LC components with the two diodes providing the energy from the drive voltage in either direction.

     

    It should work fine with low current and low load conditions.

     

    DAB

Children
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