I was recently accepted into the DorkbotPDX gallery installation at Styloid Process entitled "Connection & Suspension" with my first electronic art piece called "Conversation Piece". My favorite kind of artwork is the kind that invites you to play with it. I was inspired by the last Dorkbot show a few years back, where there were lots of fun electronic toys, plus a gallery nearby that had kinetic artwork. I had observed a cooperative play that happened at Luz parties (club shows with interactive graphics) where two people would riff back and forth as long as there were enough inputs and visible output for multiple people. Knowing this, I had gone through several ideas before I reached the very simple tin can idea. I had the separate idea to make a USB tin can that you could use with Skype, but realized that it wouldn't be practical for a gallery setting, especially with a computer, so I decided to make two tin cans that would be strung at opposite ends of the gallery, where two people would have to negotiate to communicate with each other.
The construction process was pretty arduous. I isolated the piece into its elements, which were the two tin cans and a central Arduino that would switch between the two. After reading two electronics books partway and building a dud of an intercom circuit, I went back to the source of the problem by heeding Jason from Dorkbot's advice - build an amplifier.
I started with a bare circuitboard, an LM386
, and the datasheet. I tried a few of the circuit suggestions in the datasheet and even accidentally built a radio for an hour. I did run into a strange problem in which I found out the AW5K relay's datasheet was inconsistent with how the relay actually worked, so once I flipped some wires around it was fine. I added a button to switch the relay manually since I didn't have the tin cans ready. The gain was crazy and causing my cheap speakers to have a high-pitched beep tone, so I replaced the single resistor with a 10k potentiometer (the kind of knobs you find on volume switches).
Next was constructing the can. I used a Dorkboard connected to the insides of a Wii Nunchuck that I took apart. I tried using Todbot's code, but since there was no position data and the code was a mess, I scrapped it for a thrice-adapted header file
. I simply read the position from the can and had the Dorkboard set the outgoing pins high or low based to show that it was ready to talk and to listen, and have the Arduino between the two cans decide which one gets to talk or listen.
The middle part was the hardest. I used CAT5 (networking) cable to carry the power and signal on each can to the central Arduino, which was also connected to the breadboard and was carrying 5 volts of power to the whole circuit. The relay was then connected to a Darlington transistor and then wired into the Arduino. I'm still uncertain of the approach in logic I took, but you can see the code for yourself
I am considering reworking the hardware and software after I take it out of the gallery, and finishing my original USB tin can idea as well. Overall, I am satisfied with the end result, and proud that I taught myself basic electronics in two months.
(Reposted from my original blog post at Meep in the Big City)