For the midterm project I’ve been assigned to work with Zoe.

Our wish was to play with tactile materials like sand: we discussed the possible experiences that would let people touch the sand or see the sand moving. We settled with the initial idea of designing the speaker object that would send different frequencies to the surface above and would move the sand on top of it.

We would build a 4 tone keyboard that would create different frequencies and different vibrations to move sand around and light up different LEDs. The person would get to experience two-step interaction: by pouring sand and playing with keyboard.

Components needed:

  1. Arduino microcontroller and a breadboard
  2. Battery for the speaker (we ended up using DC power)
  3. 4 FSRs
  4. 4 LEDs (or 1 RGB LED)
  5. Resistors (9)
  6. Speaker

Just to mention that the final result came out different from the initial idea but let’s go through everything step by step.

First we built a prototype on a breadboard to see if everything works. We’ve got to play again with the tone output lab and learn more about the frequency. We mapped FSRs to different tones to get different frequencies. After everything worked with FSRs we connected the LEDs.

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At first we had some trouble turning on/off only one LED as few of them came on together at once but that was because we didn’t set brightness as a global variable.

After making sure the circuits on the breadboard work super fine, instead of the piezo speaker we plugged in the speaker from the ER and played with some more volume:

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Then we put a plate on top to play with different materials and learnt first few lessons:

  • salt is not really good as it sticks together
  • sugar moves better
  • rice and buckwheat is a bit too heavy

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We also learnt that FSR’s don’t really go along with the idea as they somehow gives only on and off, so we decided to move on with potentiometers instead to be able to control a full range of frequencies.

Time to wire up a speaker! We didn’t want to buy one; luckily Gal found one on the junkshelf few weeks ago and happily borrowed it to us. Unfortunately the speaker didn’t have a built in amplifier so we had to find one (thanks TK, for borrowing one to us).

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We had some trouble with making amplifier work (it kept giving us some weird signal), but after some effort and TK’s help it worked!

The project would be impossible without a trip to Home Depot:

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We tried few different size buckets and different materials but still, vibration didn’t seem to be strong enough:

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After talking to Jed, he suggested instead of putting bucket directly on the speaker, making a connection via dowel: we would need to glue the dowel on the center of the speaker and screw the nail through the bottom of the bucket to the dowel. That’s exactly what we did. The nail served as a main carrier of vibration and made it go to the center, whereas both buckets had it strangely spread wherever.

After we did that we made few more iterations to play with different surface materials: at first we used simple plastic wrap, then balloon latex, then we bought latex sheets and finally plexi plates.

Plexi plates appeared to be the best (and last minute choice)! Of course, it meant we had to say good bye to the buckets, but everything is for the better result. And as I mentioned at the beginning that salt didn’t work, it appeared to be the best material for this kind of plexi included experiment.

References used

http://www.instructables.com/id/How-to-make-a-Chladi-plate-vibrating-membrane/

http://makezine.com/projects/chladni-plate/

Help from the fellow ITP’ers

We had office hours with TK: he helped a lot with deciding what speaker to use, he also pointed us to p5 sound library, so we ended up using serial communication instead of Arduino tone library.

And of course he emotionally was there to make the amplifier work (it somehow worked only when TK was around).

More high quality photos and video to be added.

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