Designing a pressure sensitive floor


[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.

Moolodeon electric accordion

[Lee] wanted an electric Melodeon to use with his band. A Melodeon is a chromatic accordion and there are people who already make electric versions but they are a little too expensive for him. Instead, he bought a toy accordion and added electronics to it.

After being thwarted by forgotten PIC skills of yore, he went with an Arduino as the controller. Two pressure sensors are used to detect the squeezing and pulling of the instrument’s bellows. His did some solid work. The video above uses 8-bit sounds like we’re used to from video games and the one after the break sources more traditional accordion sounds.

[Read more...]

Crushtoberfest – can you pwn Tom Selleck?

On rare occasion, the celestial bodies that control engineering and design awesomeness move into alignment and cast their blessed star dust upon a hacker. Today, we can witness the glorious outcome of such an alignment. Although almost unheard of, it’s a good omen that such a blessed hacker also be adorned with a wickedly furry face.

[Joel] wanted to up the ante for a yearly work gathering. He set out with the concept of Crushtoberfest, a test-your-strength game where a stake is hit with a mallet and the resulting force rings a bell. But bell ringing is for normal projects, [Joel's] muse required LEDs and fire as a reward for success. In fact, Tom Selleck (god of all things mustache) becomes angry at successful contestants to the point that his eyes will flash red and flames shoot out of his ears.

The mechanical input is a clever design. The stake used as the target is a 6×6 block with some old tire tread affixed to the top of them. The stake rests on a piece of radiator hose that is sealed on one end and connected to a pressure sensor on the other. Radiator hose is resilient, so it takes quite a blow to cause much compression, which is then translated into a value by an Arduino via the pressure sensor. [Joel's] gone to the effort of building gravitational deceleration into the progress tracker of the vertical string of LEDS. Too bad he didn’t have access to an addressable LED rope to make this easier, but he did pull it off nicely. He also goes into detail about prototyping and building some fireball modules.

Go now and read his blog (oldest at the top, newest at the bottom). We can call the experience nothing short of delightful.

The subway never sounded so good

Reader [Philippe] tipped us off about this video showing a set of subway steps being turned into a piano keyboard (english translation). The creators wanted to make taking the stairs rather than riding the escalator a bit more fun. They added pressure sensors to each step, then covered them with white and black keys to resemble a keyboard. When a passenger puts their weight on a step, the corresponding pitch is played out loud.

We may have lied in the title as this doesn’t really compare to hearing Josh Bell play for pocket change at your train stop. But coming across this setup on an otherwise mundane commute would really brighten up our day.