Project #2, Post #2: Electronics

In order to create a touch-sensitive vibrating function for the necklace, I needed to create electronics small enough to be embedded within the hollow pod. My original idea was to build the circuitry on a micro-/nano-Arduino. However, upon Kate’s and Heather’s suggestions in class, I visited Come as You Are to investigate the electronics that are used in some of their smaller vibrators, as these are on a comparable scale to the pod.

The Fukuoku 6000 Finger Vibe (Photo: www.comeasyouare.com)

The vibrator that was most analogous to my intended object was the Fukuoku 6000, a touch-activated, quarter-sized fingertip vibe. This device has external electrodes, which, when they are both touched simultaneously by the finger, complete the circuit and activate a vibrating motor. As this was a strategy Kate had also suggested during my proposal, I felt that this seemed to be a logical one to pursue.

Because I was unsure of the specifics required to create such as circuit, I met with Kate, who directed me to several webpages related to the MIT Media Lab’s Drawdio, a device for ‘drawing with music’ – that is, a pencil hooked up to a circuit such that when the pencil makes contact with the page when drawing, the circuit is closed, a speaker is activated and it emits a tone. This device was originally created to work using any conductive object (e.g., skin, plants, running water from a tap) as the circuit-closing mechanism. Thus, I could simply use the Drawdio circuitry, with the substitution of metal electrodes and skin contact for the pencil setup.

The main challenge of this task was the interpretation of the circuitry schematics for Drawdio that were available on the Web.

Original Drawdio circuit design (Image: http://web.media.mit.edu/~silver/drawdio/make.php)

Ladyada.net's schematic of the original Drawdio circuitry (Image: www.ladyada.net)

Drawdio schematic from Concordia University's S-Lab (Image: slab.concordia.ca)

 

I initially found the S-Lab’s schematic to be the easiest to follow, substituting a vibe motor for the speaker and electrodes for the graphite; however, once I assembled the circuit on my breadboard per this diagram, I found that the vibe motor was continuously active, regardless of whether the electrode leads were in contact. After browsing some forums, I found someone who had experienced the same problem following this diagram, and discovered that the capacitor connected to the speaker ought to be connected via its negative lead. In hindsight, this makes sense, since the electricity in a circuit flows from positive to negative. But being somewhat out of practice with circuits, it didn’t occur to me until I read it. After this, I was a bit concerned about the accuracy of this diagram, and crosschecked it with the first two diagrams, which I had initially found quite difficult to read (I found it challenging to figure out how components were connected in the first, and in the second I was a bit thrown by the strange ordering of the numbered terminals on the 551 timer.) Using the S-Lab as a sort of legend based on the parts of it that did make sense (e.g., the bypass of timer pin 5 to ground via a 10nF capacitor) to ‘decode’ the other two diagrams. I then followed those two diagrams in constructing my circuit. One of the forums I had looked at when trying to solve the capacitor orientation problem had also suggested the substitution of a 10nF capacitor for the 680pF one indicated at pin 2. This did seem to provide a stronger vibration, and so I tried different combinations of resistors and capacitors throughout the circuit. I found that using a 10nF capacitor on pin 2,  a 330uF (16V) capacitor on pin 3, and a 10K resistor on pin 2 provided the strongest and most constant vibration.

Circuit prototype.

 

Diagram of circuitry for my piece.

 

The next step was to try to fit the electronics into the pod. In order to do so, I arranged the components of the circuit on a basic circuitboard, which I then trimmed down. However, this proved to be insufficient, and ultimately, I was unable to get the circuitry to fit into the pod. I also tried soldering the elements together without using any sort of backing, but this did not provide enough support and the solder joints kept splitting.

Attempt at fitting circuitry onto a sufficiently small board.

 

 

 

 

 

 

 

 

 

 

 

 

 

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