At this point, we were just making tweaks based on feedback received from our reach demo presentation.

For one, we had been working with the pillow completely deflated and taking readings from there. Rahul advised starting with a fully inflated pillow and working from there, which we did. Surprisingly, the readings from the pillow appeared to be more consistent with a firm, almost fully inflated pillow than they were when we were working with a mostly deflated pillow.

It’s the week of the reach demo.

Miraculously, in the wee hours of the morning, we were finally able to get the integrated system working. Finally, we could use one mbed to continuously read values from the sensors and activate particular solenoids (and the pump) accordingly. It was such a relief to finally see the system coming together.

The time has finally come for the first big step: the baseline demo.

Velostat has proven to be a very difficult material to work with. It took several nights of trying to get sensible readings from different sized pieces of the material until we finally discovered a key for Velostat: to get good readings, we had to fold the velostat over two or three times. Once we did that, we could finally see observable differences between when we applied pressure versus when we left it alone.

At this point, we’re a week into the project. We decided to start with the sensing component and continue on to the actuation once we had that down.

We used force-sensitive resistors (FSRs) for our first milestone, and those worked well. However, in our initial meeting with Rahul, he suggested pursuing creating a mat of sensors. While the FSRs are quite accurate, they are also rather expensive (~$7 each), and we didn’t think it would be scalable to cover an entire mat with these sensors.

It’s the first week of April, and we’ve finally started actually working on the project!

We decided to use the mBed microcontroller as the core of the project. At this point, we are trying to tackle the first major piece of the project: sensing the position of a sleeper’s head on the pillow.