Week 11

Input Devices

Input Devices

The assignment this week was to measure something, add some sort of input device to a microcontroller board and read the sensor.

My final project requires an air pressure sensor, so I felt it was natural to test out a way to make one of those this week.

I felt the best place to start was Neil's Step Response examples since they are so adaptable and I figured if I could get one working, I would be able to build a housing around the pads to work with air pressure.

I first started with the straight TXRX Board as designed to make sure the general process works.

I had no problems making the actual board and arbitrarily chose the size of the copper pads for the raw sensing. Running the example python code worked great once I figured out the syntax and how to identify serial ports correctly I got the board talking to my computer and correctly sensing when I touched the pads! Video below!

The next step was to make the board my own. I redrew it in eagle, all of my files are available in my file repository. Once milled out, I wanted to play around with a pressure sensor and carefully made my copper pads for a second try. I made perfect 4" squares and mounted them on an acrylic base. I then ran foamstrip around the border to offset the panels and allow me to push them together with some resistance, hopefully being able to measure pressure.

My complete TXRX pressure setup

Detail on the pads

The new board works, but I'm not certain that the pressure pads have enough sensitivity to measure differences in air pressure. They work if you press extremely hard, but subtle changes do not register. For my final project I will likely increase their size to increase capacitance and likely seal the entire setup to make it consistent/allow air pressure monitoring.