DIY

CIRCUITS

Shock the monkey: Sensor-equipped sock monkey changes its tune as it twists and contorts.

MIDI CONTROLLER MONKEY

A/V monkeyshines with flex sensors and a MIDIsense board. By Peter Kirn

Who said input devices have to be hard and mechanical? Here’s one that’s as soft, bendable, and easy to play with as a plush toy. In my MIDI primer (MAKE, Volume 07, page 158, “MIDI Control”), we saw how to use the MIDI data specification, originally designed for music, to interconnect both musical and non-musical hardware and software. Now, we’ll use this approach to construct a sock monkey instrument you can use to control visuals and sound.

The monkey has flex sensors sewn into its limbs, and it wears a sensor interface board as a backpack. The sensors detect the monkey’s movements, and the board converts the readings into MIDI data. This lets the monkey conduct audio-visual symphonies and perform other MIDI magic.

Circuit Bending

Designers have long used off-the-shelf sensors to translate real-world movements into digital realms. For this project, we’ll use one of the most commonly used types: a flex (or bend) sensor. This type of sensor was designed by Abrams/Gentile Entertainment and used in the infamous Mattel PowerGlove (a game controller for the Nintendo Entertainment System), as well as in the more recent Essential Reality P5 gaming glove.

The concept behind a bend sensor is simple: its electrical resistance changes as it bends. This lets it work in a circuit just like other resistive sensors, such as light sensors or potentiometers. Variations in voltage that result from bending can be converted to a digital value and trans-

Photography by Peter Kirn

142 Make: Volume 08