Velostat SmartSurface

Velostat sensor
Circuitry behind the sensor
Our Mascot

Inspiration

Once I heard about Velostat, I knew I had to do something with it. I have come up with so many ideas for projects, but this is the first time I have had a chance to use it. This project is a first step into the pressure sensitive world of Velostat.

What it does

A matrix of wires across the Velostat feeds into the analog inputs of an Arduino board. From there, the data is sent serially to a computer where we run calculations and plot the surface in Mathematica.

How we built it

We started with just a simple closed circuit with the Velostat as a variable resistor and calibrated it as a single force sensor. We then created a matrix of conductive tape to run across the Velostat at 25 different points. As we developed the hardware, we decided to implement some Mathematica code to visualize our results.

Challenges we ran into

To calibrate the pressure sensor, we needed a series of data points to fit a curve. However, we had no access to any known masses or a scale. We did have some 500mL water bottles. To approximate the pressure resistance curve, we poured water from one bottle into another resting on the sensor. We sampled at a constant rate and tried to keep the flow rate consistent too. After a few tries, we found a curve that fit.

At first, when expanding the sensor to a matrix, we neglected to account for the huge change in resistance. For hours we struggled to figure out what was wrong. Even once we figured it out, we had no solution. Then, we realized that we had some transistors, so we could make switches to get around the output impedance problem. We eventually found a new power source to use with the switches and saw immediate success in our results.

Accomplishments that we're proud of

We are proud of the improvised solutions we came up with in the face of limited resources.

What we learned

Neither of us had ever used Mathematica before, but we were happy to pick some up. Shout out to Kyle from Wolfram who was a tremendous help.

What's next for SmartSurface

We hope to develop the Velostat pressure matrix for more specific applications. It has a wide variety of possible uses, from healthcare to security. We'd like to further develop the technology and explore these areas.