AC frequency efficacy

Hello all,

Its been a little over two weeks since I had a magnetic disk implanted in my left ring finger, and its gotten sensitive enough to where I can start feeling things. This has led me to start messing around with inductors for devices, and I'm getting some questions along with results.

This first one is more for the folks over Grindhouse Wetware and those familiar with the Bottlenose, but maybe others too.
What electromagnet is typically used in the Bottlenose? Is it a commercial ferrocore inductor like you find in any computer PSU, or that can be bought online, or is it just an air core inductor (coils of wire that slip over the finger), or maybe something else?

I also wanted to share an observation and ask another question.
I have a prototyping board with power supply, wave generator, digital outs and an oscilloscope all rolled into one (,842,883&Prod=EEBOARD if anyone is interested) that I have been using to test different wire coils and I just started messing with an AC waveform input just to see how it differed from the DC input. The board can only send out a signal of up to 4 MHz, so I was working with sine waves at 3.3 V between 10 Hz and 4 MHz. The strongest constant vibration was between 200 and 300 Hz. Below that there was a weak, constant vibration and from about 250 Hz and up there was (in addition to the constant vibration which dropped out at ~400 Hz) also a pulse every few seconds or so. It was fairly minor, but when there was no constant vibration it was easy to detect.
I was using 22 gauge wire with insulation still on, 9 coils at ~.5in diameter btw.

I'm not sure if that is going to be useful information to anyone, but its now here if anyone sees fit to use it.
Is there any data already available about how different AC frequencies affect magnetic implants? Or what differences there are between AC and DC currents in regards to magnetic implants? I dunno what practical use this info would have, but I'm starting to become interested in it.

Mr. Sticky


  • the response you get over the frequency range depends on many different things.
    on the magnet that's shape, size and density of the magnet.

    for the coil that's mainly the induction. in case you have an electromagnet with core, saturation effects may also play a role.

    the theory , in short version is. the voltage you apply to the coil causes a current to flow, which causes a magnetic field to build up. coils resist against fast changes in current. so the higher the frequency, the less current change you get. and the magnetic field's amplitude will decrease. so at high frequencies you'll get a static magnetic field. much like when you DC power the coil. as this effect is directly connected to the current flow. you can simply monitor the current flowing to observe that effect.
    the other big part is the magnet. or more precisely its inertia and moment of inertia. when you change the magnetic field , the forces that apply to the magnet will change, the magnet will then accelerate to follow those new forces until a new force builds up that acts against it (that's the tissue of your finger).
    your tissue can only build up a force acting against the magnets when the magnet actually moves a bit (since tissue is soft). that movement is what you sense too.
    if the field changes too fast forth and back, the magnet can't accelerate long enough to result in any motion.

    systems like that often have a resonance frequency somewhere.

    and. ontop of that, comes your sensing abilities and how your sensory works. unfortunately i have no precise information on that.

    i'd be interested in a smal graph that shows the amplitude of the AC-current through the coil, aswell as the level of sensation you get. mapped over the frequency range.
  • I'll work on that graph, maybe using different commercial inductors as well as different coils (more for my own use, optimizing the field for my finger). It should prove to be a good distraction for part of an afternoon. It might be a bit before I get around to it, but I'll post it when its done.

    Mr. Sticky
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