This device makes use of electro-magnets to actuate ferrous materials, such as a steel string or plate. This allows for an instrument to be played without coming in physical contact with it. This is similar to an e-bow, but with a much more focused range allowing for a more intense actuation of specific frequencies. Using this technique, we can explore the harmonic content of any ferrous material and use it to influence our relaxation practices.

To do this, we will use materials from an electric bass, which are essentially:

  1. Wood (approx. 32’’ length)
  2. String (I used a standard D’addario D-string)
  3. Mono-string bridge
  4. String Tuner
  5. Electro-magnet 40mm (Amazon)
  6. Arduino Uno ()
  7. N-Channel Mosfet
  8. Power supply 12v

All these materials are available on Amazon.com (maybe not the wood)

Step 1: Materials

First off, let's get some supplies:

  1. Bass strings
    I tend to gravitate towards lower frequencies so I chose to use electric bass strings, but you can use guitar strings if you prefer. Guitar strings would provide higher pitched and "brighter" tones, while bass string allow for lower pitched "warmer" and "rounder" tones.

  2. String tuning peg + Monorail Bridge
    We need a mechanism to tension the string. Since we are only using one string, let's use a monorail bridge system and a single string tuning peg.

  3. Electro-magnet
    To actuate the string, we'll be using and electro-magnet. An electro-magnet is a coil of wire (usually copper) that generates a magnetic field when provided with electricity. If we provide electricity to the magnet at a frequency rate equal to those found in the harmonic spectrum of the tensioned steel string, then we can cause it to resonate at that frequency (and many frequencies within it!). We also need this magnet to be powerful enough to manipulate the string so let's go ahead and use a 12v 40mm.
  4. Hardwood (I used Walnut)
    Like many acoustic instruments we need some sort of resonant chamber so the sound can be amplified and characterized. Hardwoods are good because they are dense enough to carry the frequencies throughout and add character to the final sound. Walnut is generally thought to produce a warm tone with good mid-range.
  5. Arduino Uno
    We will be using the arduino's Tone library to generate squarewave frequencies that switch on/off very rapidly to pulse the electro-magnet with electricity.
  6. N-channel Mosfet
    The mosfet will act as a gate between the power supply and the electro-magnet, it is controlled by the Arduino
<p>Question. I'm having trouble with my electromagnet. Everything works fine but the magnet is buzzing a lot. I thought it was hot, so I added a heat sink. It is not hot now but was still buzzing. I removed the magnet from the box and it is fine away from the box. Anyone else have this problem? It is just vibrating the wood because even if I just set it on the wood it is a problem. Any suggestions? Did you use some glue or material that isolated the magnet from the wood? Thanks, in advance, for any thoughts.</p>
<p>Great instructable. I added a heat sink to the magnet, as it is still 60C with the sync. Also a voltage regulator so I can get 5V and 12V off the power supply. And I added a rotary pot to the circuit so I could fine tune the magnet. I had a lot of trouble with everything, because I've never made anything like this. I've never even made a wooden box. I'm hoping to make up an idiot's guide to how to make this, and throw in the few mods. Perhaps folks will be able to tell me how to stream line things. Great job EpicJefferson@!</p>
<p>This is great! Good call with the rotary pot for finding the frequency, so much better than tuning the string every day ;)</p><p>Excellent work.</p>
<p>Yes, and positioning the electromagnet at an antinode will help a lot. If you pluck the string and look at it under a tube fluorescent light, you can get an idea where they are. </p>
<p>I'll have to try that. Although you can also put it where it sounds good ;)</p>
<p>Very good!</p><p>There is a Brazilian plastic artist, named Paulo Nenflidio, who has works following this concept.</p><p>See some:</p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/tWJgVcVSvkk" width="500"></iframe></p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/GE51Q7RQBd4" width="500"></iframe></p>
<p>Thanks for the good vibes ;) </p><p>I'll be sure to check out more of his work.</p>
<p>Beautiful. Great wood selection and clever save on the lid. Looking forward to the next project - it's gong to be good</p>
<p>Sounds good to me ;)</p>
<p>Gong - ding dong xD</p>
<p>The cymbalism is deep and profound, I've heard</p>
<p>or maybe OMMMM</p>

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