I had an unexpected break through on my C3 project! A couple nights ago, I had some spare time, and had been thinking about the pressure sensor for a long time. The problem with it is, there is a circle with a radius of just 4mm, and in order to get good readings, the force must be applied to the center, not the edges. This gives me only about 2mm’s in radius to apply force in. Since this will be under my mattress where things can be jostled or move around, that’s a pretty narrow margin of error.
With this in mind, I came up with an idea for a “puck” and threw it together in Google SketchUp:
I was blown away by how easy SketchUp was, I learned the program and made this model all in less than an hour. What you are looking at here, on the right is the base of the puck. The sensor will sit at the bottom of the trench and be held in place by it’s constrained neck. And the left is the top, that will insert into the trench, and the notch will hold it perfectly in place, while the nubbin will be the only thing applying pressure, and it will be held perfectly on the 2mm pad.
So I brought it home, marveled at how this thing that had been in my brain just two nights before, was now sitting in my hand, and set to programming my Arduino. Came up with a voltage divider so I could get good values out of it, and calibrated it so I could convert the values to readings in pounds. Then I set it up to record a full night of sleep, and dump the contents to a text file on this little net book.
And it functioned perfectly!
You can even see when I got out of bed near the beginning there!
Despite these resounding successes, I hit the same wall I had been at for a while now. The standard Arduino, as well as the available WiFi shields, really weren’t up to the scale of the project I had in mind. And the new Arduino Due and the official Arduino WiFi shield which might solve my problems, are seemingly never to be released.
After a day or two of mulling this issue over in my head, I began perusing SparkFun as I am want to do. And I came across the IOIO which I have seen before, but this time it sparked (see what I did there?) a sea change in how I was thinking about this project! So many of the things I wanted the project to do (Like WiFi, NTP, Google Cal sync, Text-to-Speech) are exceedingly difficult for little 8bit Arduino’s to do. And other things I wanted the project to do (interfacing with a variety of hardware sensors) are difficult for Android phones to do.
But my change in thinking was to treat my Micro-controller merely as a “Sensors Package”. Which a custom Alarm Clock app on my phone will communicate with in order to be smarter than it could be on it’s own.
So that’s what I’m doing! I’ll hook my sensors into my IOIO (pronounced yo-yo) which will connect to my phone via Bluetooth. And my Alarm App which I will make, will utilize the sensor data to do everything I had hoped it work! And more!