I wanted to create an oscillating magnetic field using an electromagnet which is rated for 12V continuous duty. I was thinking that I need an arduino to control the electromagnetic circuit by using a transistor. However, after doing some research, if I wanted to create an oscillating magnetic field that oscillates 1000 times a seconds, it would not work as the electromagnet would probably not respond that fast.

So I was thinking that maybe doing some research on an LC circuit or an H bridge would help me with my goal. But I needed some guidance as to whether or not there are other issues with my plan that I need to think about and where I should go to get the information I need?



1 Answer 1


To make sure the inductor will respond that fast, you need to solve for the size of the inductor (which will make your magnetic field) which will be resonant at 1000Hz when coupled with a capacitor of convenient size.

luckily, an old-school stereo speaker containing a woofer and a midrange speaker will contain a crossover network which has in it an inductor and a capacitor that are resonant at between 800 and 1200Hz, so that the lows get sent to the woofer and everything else goes to the midrange. If you can scrounge the inductor coil out of the crossover network you can be sure that it will support a 1000Hz signal.

  • $\begingroup$ Sounds interesting, But I would need to find a speaker for that. I imagine I should just be able to find the parts and build it myself or create the LRC circuit to resonate at the high frequency. Just two questions, would the H bridge be able to do the same thing but easier? And lot of electromagnet manufactures don't tell me their response rate, so how would I know which one will be good without buying it? $\endgroup$
    – Jeff Boker
    Commented Jun 15, 2020 at 16:14
  • $\begingroup$ here is what to do. go out to a DIY site for hi-fi enthusiasts and look for an instructable on how to wind your own crossover coil for a 1200 Hz crossover frequency. If you can't find one I'll look in my parts bin and see if I can find you one and mail it. What is this going to be for? $\endgroup$ Commented Jun 15, 2020 at 17:09
  • $\begingroup$ I want to create this high frequency magnetic field using cheap stuff to see how it interacts with some magnetic beads attached to different materials. Do you happen to know which particular speakers might already have the parts and I can just buy them? $\endgroup$
    – Jeff Boker
    Commented Jun 17, 2020 at 23:57
  • $\begingroup$ Nope. the crossovers cost a fraction of the price of a set of speakers, which are rendered useless after you remove the crossovers. Let me check my parts stash. Note that the cheap way to drive the coil is with an audio amp that is connected to a sine wave oscillator set to 1000Hz. $\endgroup$ Commented Jun 18, 2020 at 4:37

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