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Jim Mettler -  Power Magnetics Expert at Triad Magnetics.

patkelly

Jim Mettler -  Power Magnetics Expert at Triad Magnetics.image

 

Jim is head of engineering at Triad Magnetics, with expertise in Power Magnetics from fractional watts to  hundreds of kilowatts.

 

Jim and his Triad team have extensive experience developing Power Magnetics for product applications including alternative energy, Smart Grid, metering, lighting, appliance, industrial, commercial, audio and medical equipment markets.  They create custom designs unique to the industry, balancing cost, size, temperatures, and efficiency for elegant solutions.
 
With more than 28 years in the transformer design industry, including 12 years as the key Design Engineer at Triad, Jim has widespread knowledge of products utilizing Power Conversion, Measurement and Conditioning technologies. His years working closely with diverse customers to solve difficult design questions have made him an industry expert in power magnetics.
 
Jim’s passion for power carries over into his personal life, as he’s designed and built his own battery powered motorcycle that he enjoys riding through the hills of California. He also powers off road in his 1975 Pinzgauer Swiss military vehicle.  In his spare time, he’s a docent at world famous Palomar Observatory, and volunteers for “Star Parties” at local schools, setting up his 12-inch Meade LX200 Schmidt Cassegrain telescope to teach them the science behind the stars.
 
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  • Welcome, Jim!

    Will you help with my project?  ::  A 9V battery pulses a coil of magnet wire under control of an arduino via H bridge.  What is the number of loops (small number is better so it can be hidden under a paper or plastic covering) and their diameter to be able to effect movement of a small neodymium magnet at one inch?  They will not come together but the magnet is mounted on a moveable pendulum.

  • in reply to billabott

    Hello,

     

    Hmm, interesting question with a lot of unknowns.  But maybe I can steer you in the right direction:

     

    The force that you can apply is dependant on the Amps * Turns of the coil, the distance (you have fixed that at 1"), and the coil diameter.  If you just think about the general geometry of your system, an average coil diameter of 1" is probaby a good fit for your 1" distance.  That would mean that a 1.5" OD coil with 1/2"ID would have a 1" average diameter.  But the small diameter turns in the center do not contribute as much, and the outer turns have such a large diameter that they contribute a disproportionally large amount of resistance.  Of course you can use whatever size you feel is appropriate to your project, but this might be a good size to start with.

     

    To maximize the force (all other factors being equal) you need to maximize the volume of coil.  This allows maximum turns, with the maximum wire size to minimize the resistance (and therefore allow the highest current).  In other words, to double the force you must double the coil volume.

     

    The balance of the turns and wire size (one turn of a huge conductor, or a million turns of a one millionth area conductor) is chosen to best match your drive impedance - the best match of your source voltage and available drive current.  Since you said you were going to use a 9V battery (and I'm assuming you want the battery to last for two weeks, we should limit the current to 2mA or less; and if we assume that the pulses have a small duty cycle of 5% then the pulse current could be close to 40mA;  9V / 0.040A = 225 ohms, so using a fine wire and enough turns to get in the neighborhood of that resistance will best match the source impedance (obviously, if you want the battery to last for months or years you will want less current, or less duty cycle, which will change the DCR goal of the coil).  Now the puzzle of how much coil volume you need to get the force that you need comes into play, and the continuing puzzle of what wire size and number of turns gets you the the desired DCR of the coil... this is just one of the reasons that Magnetics is considered such a black art, but most of it can be fairly easily determined by a few trial and error attempts (especially when there are unknowns).

     

    I hope this helps get you started.

     

    Kind regards and good luck,

     

    Jim

  • in reply to Former Member

    Thank you, Jim.  That is an excellant discussion of the issues involved.   Great work!