Building a 3D-printed, Arduino-powered robotic DJ

This robotic DJ may be able to scratch vinyl records better than you. 

Texas A&M student Rico Balakit has come up with a slick idea quite literally from scratch. The Maker has created a 3D-printed, robotic device capable of controlling a crossfader with Jazzy Jeff and Grandmaster Flash-like precision.


For those unfamiliar with the DJ technique that dates back to the mid-1970s, scratching (sometimes referred to as scrubbing) is used to produce distinctive sounds by moving a vinyl record back and forth on a turntable while manipulating the crossfader on a mixer — a task in which Balakit wanted to automate. The aptly named ScratchBot was synchronized with Traktor, while an Arduino Mega (ATmega2560) was tasked with keeping the tempo of the song being played.

“Traktor uses MIDI standards, so it was pretty easy to figure out that I’d need to interface with MIDI and process it. To start, I installed loopMIDI, which creates a virtual MIDI port Traktor can output to, and Hairless MIDI, which converts that MIDI into some serial stuff thingies the Arduino can handle,” Balakit writes. “Then, to get it to actually sync with a song, on the beat, I used the ‘Beat Phase’ MIDI-Out on Traktor to get it to reset the counter to zero when the beat-phase value for a beat having passed is received.”


The Maker wanted the Arduino-based robotic DJ to perform in two different modes: one where pushbuttons are assigned to pre-programmed scratch routines, another where it employs music loops and random patterns.

The system itself consists of two mechanisms. The first, a simple crank powered by a single servo and attached to the mixer that gates a crossfader. The second, a swinging arm enabled by a pair of servos. One servo pivots directly over the turntable’s axis of rotation and controls the scratching motion, while the other commands the arm whenever it’s pushing down on the vinyl record.


Intrigued? Head over to ScratchBot’s detailed project page to see a step-by-step breakdown of the build. In the meantime, watch in action below!


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