This is an all-digital-hardware Theremin. The Digital IR Theremin uses comparators, digital logic and a single 555 timer for tone generation to make it so that when you wave your hand in front of the infrared proximity sensor, it outputs a tone with varying pitch depending on how far away your hand is from the sensor!
The Theremin first came around in the 1920’s and provided us with a host of spooky, creepy sounds and so naturally being able to make one at home with standard electronics is a must. A standard Theremin uses two antennae for pitch and volume control. For this project, we will ignore controlling the volume and just look at controlling pitch.
IR sensors used to detect the distance between the sensor and an object are a perfect fit for a DIY Theremin because they are low cost and they are reliable enough to get the project working. The idea here is that instead of using antennas, we’ll use infrared proximity and be able to play an instrument, the IR Theremin!
Halloween is always a great opportunity for hackers to take their creative projects to the streets. This year at NerdKits, our Halloween costume is the Human Theremin. The costume features two homebuilt infrared distance sensors mounted on the wrists. Someone wishing to “play” your costume can move his or her hands up and down above the distance sensors. One hand controls the pitch of the note, and the other controls the volume.
All said, we hope our costume is a big hit at Halloween parties, particularly because it allows others to interact with the costume (and can be really loud!). As always, we cover in-depth the concepts behind the electronics and code that we publish. This video can be a great introduction to phototransistors, triangle waves, fixed point math, and more, to help you learn and extend these techniques to your own projects. Happy Halloween!
Theremin Style Instrument: This battery powered electronic musical instrument is a descendant of the theremin and can be played without contact from the musician. This easily – assembled, small instrument contains two infared (IR) sensors, one controlling the note, with the other controlling the octave that is played through the speaker in the front. There are seven possible notes (c-b) and 7 possible octaves of each note. The tone is reflected by one of seven colors that illuminates the center area and highlights a small indicator located on the top panel. The brain of this piece is a boot-loaded atmega chip. The source code is available, as well as, pictures and a video. Check it out here: