Couple of month ago I was commissioned to build an interactive carpet for kids prototype. The concept was a carpet with cute animal faces on it, when a kid steps on it the sound of the animal is played via a Bluetooth speaker. I had about a week to build it. The biggest challenge was how to sense where the person is standing and that too without adding any thickness to the carpet. The pressure sensor could be used but the carpet size was about 2’x4′ and the animal faces were quite big as well so in terms of cost and the number of sensor and system complexity it was not used.
After a lot of thinking and googling, I used off the shelf 4×4 membrane keypads as sensor, this cut down the costs and also was simple and a robust solution for a quick prototype. Under each animal face I connected the keypad in parallel, so any key press in a group of keypad will send out a signal.
Before jumping on the sensors I tested out the electronics and spun off the code to play music when IO is triggered.
Here I’ve laid out the keypads for connection.
There was a big window were I was working and held the carpet against the light and drew the animal outlines on the back so I know how the sensors are connected.
This whole system was to run on batteries and it was showcased in New York, so I had to use AA batteries for easy replacement. I also designed the case which was laser-cut, and a soft black cushion box was also made by a tailor. In order to make and break the connections I used snap buttons.
After all the connections were made all the keypads were taped down as it had a long way to travel and there was no technical guy at the event.
The final result looks like this
Check out the video of the prototype.