This weekend we collected the materials and sensors for our Channels installation. Ginny, Alvin, and I piled into my Subaru wagon and spent a couple of hours scouting materials and testing structures in the Lowes shopping aisles. Once we saw the range of materials available, we were able to firm up our construction design, which ended up differing slightly from our original plan. Instead of building rings of 4-6″ PVC piping and using insulate board for the body of structure, we selected 15.5 gallon metal tubs and a wooden stool, and some pieces of wood paneling to construct the hull of the boat. We also bought this Amazing Goop that we used as a translucent waterproof adhesive to glue the pvc pipe halves to the insides of the metal buckets, which creates a circular channel for the water to flow around when a person paddles in the water.
We knew that the structure of the large metal buckets would work for our purposes because earlier in the week we had tested the concept of water swirling around in a circular motion inside of a large mixing bowl. We built our own simple version of a flow meter using a flex sensor strip with a “flat paddle” taped on the end of the strip.
We tested this sensor design with the Arduino and got pretty accurate and smooth readings when we churned the water in a bowl with our hands.
See our quick demo video of this sensor working in water.
Originally, we had considered ordering this flow switch part from Seeed Studio, but the shipping from China was estimated at 10-30 days and we couldn’t wait that long for delivery. Fortunately, however, our own sensor design works as a decent substitute.
We went through several iterations of designs for paddles. We used old credit cards for the sensor paddles because we thought they had a greater surface area and thus provided more resistance against the water than our original circle paddles.
Finally, we decided to use half of a plastic spoon for our paddles because the scoop helped improve the paddle function and the plastic was lightweight. This turned out to be the perfect balance of size and shape that worked consistently with the bend of the flex sensor strip against the water current.
The most critical part of our sensor design was to secure the soldered connection point with a rigid outer-covering so that the flex sensor did not bend in a vulnerable place at its neck. We cut out a square brick of insulate foam, and inserted the flex sensor inside the foam brick, but this was NOT enough. We broke 3 flex sensors before we perfected our design.
In the end, this is what we did: 1) we soldered the connection point and strengthened the soldered point with hardened hot-glue, 2) we taped half of a plastic spoon to the end of the flex sensor strip, 3) then we cut out flexible plastic strips about 3 inches in length, and taped them firmly around the flex sensor strip from top to bottom in order to encase the entire strip and make it waterproof (which also helped it from bending too far back and forth), 4) we taped the encased flex sensor strip to the side of a piece of foam brick to secure it in place, 5) then we attached (with very strong glue) the foam brick to a piece of wood that was suspended above the water current across the top of the metal bucket.
Our team built an amazing wooden boat, with advice and guidance from Peter Menderson, Adjunct Professor at ITP.
We stained the boat with a dark cherry finish, and used the laser cutter to print the name “Ginny” on our boat.
We’re focusing on the physical form factor especially, so that people feel comfortable when seated in the “boat”. People are different sizes and heights, and we want children to be able to participate as well, so we are aiming for the average measurements in our physical placement of the seat and water tanks.
Things to do next:
1) Solder circuit to perf board and stage the installation with short-throw projector.
2) Test sensors in water and map range of values to speed and direction so that movement is smooth and responsive.
3) Compile sound effects and create audio soundtrack in Audacity, import Minim library to our Processing sketch.
4) User testing; get general feedback on all aspects of installation.
Read more about the background for this project in last week’s blog post.