Maker
Set in Stone
An interactive concrete interface. By Ithai Benjamin and Vikram Tank
Set in Stone is two concrete tables that interact with each other when touched. The tables’ embedded LEDs are unlit, until you
touch one table — then the other lights up. Each
time a table is touched, it changes the pattern on
the other.
We made Set in Stone for N YU’s Interactive
Telecommunications Program’s Winter Show. The
materials include a bag of concrete, a few hundred
feet of fiber-optic cable, 400 LEDs, an Arduino
microcontroller, and some LED drivers.
The concrete blocks are 13"× 13"× 2" and weigh
30lbs. They were cast with 400 fiber-optic cables
and hookup wires. The LEDs were connected to
nine LED drivers controlled by an Arduino.
We laser-cut a grid of 400 holes into two 11"× 11"
plexiglass panels, which we used as an interface
between the fiber-optic cables and the LEDs. One
38 Make: Volume 19
plexiglass panel had small holes to fit the fiber
optics; the other had larger holes to fit the LEDs. To
make the display touch-sensitive, we ran solid-core
hookup wires from the concrete blocks to a QProx
sensor, also wired to the Arduino.
Each LED shines through one fiber-optic cable.
We inserted them into the holes of the appropriate
plexiglass plate and wired them together. Wiring
the LEDs is simple — the positive LED leads in each
row are soldered together, and the ground leads
are soldered together — but it’s also tedious. After
wiring, we connected the LED matrices to LED
drivers, each of which controls an 8× 8 LED matrix.
To cast the fiber-optic cables as a grid in the
cement, we used a piece of 13"× 13" foamcore
board, poked holes in the foam (using our laser-cut
plexiglass as a template), and stuffed it with the
fiber-optic and wire pairs.
Photography by Vikram Tank and Ithai Benjamin
