rebecca's WIP

[pcomp final] Week of 11/17 progress

Our focus this past week was to work through any remaining questions / problems with our sensors. We made sure they work and give us the ranges of data we need to produce expressive sound. We also experimented with different ways to get different kinds of data from our sensors (ie. watering the plant versus spraying it, changing position and direction, etc.)

Below is a run-down of what we did (and did not) accomplish from our week 2 goals:

Build DIY soil sensors and capacitive touch sensors
This past week, we put aside our sensors from Adafruit and decided to experiment with some other ways to sense soil moisture and capacitance. We first built our own soil moisture sensors using some galvanized wire and a foam block, and found that using the longer probes was helpful for getting a wider range of readings.

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We played around with watering vs spraying, and with positioning the probes going down into the soil versus facing up. They seemed to be most responsive when you water the plant with the probes facing upward, just poking out of the surface of the soil. The spraying was not as successful as we had hoped.

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If we go forward with watering the plant rather than spraying, we’ll need to figure out how to control the amount of water that goes in so we don’t drown the plant. In class last week Justin suggested using some kind of sonic cues to signify “water me” or “don’t water me,” so we can look into that. We can also experiment with limiting the amount of water we give people. Either way, we’ll need to go back to our system diagram and revise it slightly.

I also wanted to try capacitive sensing using the CapSense library for Arduino as an alternative. Last week we tried the capacitive sensor with a breakout board from Sparkfun which was responsive but might be more than we need. Plus we don’t want to poke holes through the leaves of the plant, nor do we want visible wires. So, I used the basic capacitive sensing circuit but rather than use a piece of foil, I attached our sensing wire to the stem of the plant using an alligator clip.

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And it worked! The plant became touch sensitive. I found that the range of values varied depending on the value of the resistor. I also tried adding a capacitor which made the values a bit wonky. Things also got weird when I plugged my laptop into the wall socket (I think it has something to do with the way that “grounds” the circuit). Next step is to look more into my wiring and figure out the best way to make a stable circuit.

Build and test contact microphones
Nick is currently working on building some contact microphones from piezo discs. The amplification circuit is more complicated than expected, so he had to get some additional parts.

Finalize exactly what we will be using and update our system diagram
As we’re finalizing our sensors, a lot of questions came up around the experience for our users. How do we make it so that we don’t overwater the plant? Is spraying versus watering better? Which is more satisfying? How do make sure somebody doesn’t dig up our soil sensor if they’re aerating the soil with a trowel? I think the answer to this is to have each plant be a specific interaction: you water one, you touch one, etc. Either way, we need to go back to our system diagram and finalize it now that we know what sensors we’re using.

Order any remaining sensors (IR, additional soil or capacitive sensors)
I think we’ll be mostly making our own sensors, so at the moment we don’t need to order any additional pre-fab sensors. We may be using an IR proximity sensor, but we want to test a few different kinds from the ER before

Sound development
Nick has been leading all the sound development for the project thus far and successfully schooling himself in Max MSP. We’ve been tossing around some sound references and will be pushing that part of the project in the next week, so that we have a close to final draft of the sound for our user testing on December 1. I’m planning to plug in to that part of the project more in the coming weeks so I can learn a bit more about sound and also about Max MSP.

Hook up sensors to Max MSP and get our serial communication working; set up the system fully on 1 plant to make sure sensors are reading data and producing sound
Yes! See below. The test sound we’re using is a bit grating but our communication is up and running.

Draft final plan for planter box and make cardboard prototype; order wood and any additional materials, including garden tools or other props
This past week, I prototyped the planter as part of my intro fabrication class (see this post). The biggest challenge will be making sure our electronics are safe and waterproof. We have a follow up meeting on Tuesday with Ben Light to discuss our final design for the planter, and we’re planning to purchase all our materials (wood, etc.) this week. The goal is to have the planter constructed for our Dec 1 user test.

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