Monday, December 12, 2011

Sensors, Micro-controllers, and Actuators, Oh My!

        Well, we are discovering just how complex the world of sensors and actuators is. We've brainstormed what type of sensors we want to use for each activity we are tracking; some are significantly easier to find sensors for than others. We will be using a heart-rate monitor for exercise, RFID tags to track your location (if you have entered a dining hall we assume you have eaten, if you're in the same location as a friend you are likely to have made a social connection). Finding a sensor to measure sleep we are still working out. We thought maybe we could use an accelerometer to measure movement and when the person is moving less they are sleeping? That still poses problems for sitting still or when people move around in their sleep. We'll have to keep thinking.
        On top of that, actually choosing which system to find our sensors and actuators has proven to be a rather substantial process in and of itself. Initially we had thought we could use wireless sensors because we didn't want there to be a large amount of wiring going on inside the suit making it uncomfortable. We thought that in an ideal world maybe the sensors could use bluetooth to communicate with a computer somewhere (or, in our early stages, the mobile phone), but it turns out that would be incredibly complex and significantly more work and money than is necessary given the scope of our course.
        Next, we looked into phidget sensors and actuators. We spent a lot of time on different electronic gadget websites but I don't think any of us really knew what exactly we were looking for, we were just sort of exploring and trying to see what was out there.
       Kat struck what we thought was gold when she discovered Lilypad Arduino, a wearable micro-controller. We got really excited about that platform, especially because it has a wonderful range of sensors and actuators that we really would want to use including a light sensor (maybe that can help with our sleep sensing dilemma), a vibration board, and a buzzer! Plus, we watched a video tutorial for the Lilypad and you can even use conductive thread instead of wires which, in our eyes, helped to solve our excessive, uncomfortable wiring in the suit problem. When discussing the Lilypad with Orit and Consuelo, however, we discovered that the Lilypad as a micro-controller is actually fairly week and has shown itself to be a serious headache for other project groups in the past. I had already been wondering about all the sowing that it would require and how we would prevent wires from getting crossed in the process so that conclusion made a lot of sense. Consuelo recommended we still use the Lilypad sensors and actuators but instead solder them to wires connected to an Arduino board.
        So, there you have it! We have finally settled on using Arduino to program our suit. And, after much debate about how to measure water intake including force sensors, pressure sensors, and weight sensors, I found a water level sensor on SparkFun! What a relief.

Aren't they pretty?


Oh! I also came up with the idea of having a button on the suit that you can push if you want to turn the feedback off for a little while. It occurred to me you might not want the buzzer to go off during class. I don't want the wearer to have to remember to turn the feedback back on, though, so maybe the button could just last for 70 minutes and then it would turn back on automatically?

No comments:

Post a Comment