[Sean] and his team at Adobe were asked to build “something new” for the Children’s Creativity Museum in San Francisco, so in several months they managed to build a digital/physical environment for kids called “Sense It”.
Part of this project involved designing and building a pressure-sensitive electronic floor which could detect if children were sitting, walking or running. As a camera based detection system couldn’t give them the type of precision they wanted, [Sean] decided to use pressure-sensitive resistors placed under MDF panels.
There are a total of twenty-one 2′x4′ tiles, each one including 8 pressure-sensitive resistors and an ATtiny84 based platform. All the microcontrollers digitize their 8 sensor signals and send their conversion results to a beaglebone over a shared i2c bus in a RJ45 CAT5 cable. As it is [Sean]‘s first project, we will cut him some slack but several design mistakes have been made in our opinion:
- Using i2c instead of RS485 / CAN for long distance data transmission
- Digitizing the sensor voltages so far from them, as noise is added before the ADC
- Sending the +5V required by the ATtiny in the RJ45 cable instead of a higher voltage (which would involve putting an LDO on the platforms)
- Separating the digital and analog ground planes as the platform current consumption is low and transmission speeds slow
But the children who can now play with the complete system certainly won’t care. And you… what do you think of [Sean]‘s work? Don’t hesitate to let us know in the comment section below.