Musical Junk Robot

Research project on the development of new tools for musical expression at the University College Ghent


a junk playing robot

dr.Godfried-Willem RAES


[Nederlandse versie]


One day, early spring 2009, and old lady living in my street asked me whether I had any use for thousands of old telephone relays. Her husband who just died was a devoted addict of model trains and used relays for his hobby. I decided to accept the offer and carried the whole load (many hundreds of kilos) from her cellar and attic home. There I was now, with thousands of quite large relays dating from the sixtees. I had to find a use for it. I remembered that some thirtyfive years ago, I did setup a musical automate 'Bellenorgel' using relays as memory components and building shift registers from them. But now, I was'nt feeling like repeating the past... Sorting out the entire load took me a few days. Some types looked quite intriguing and I tried converting them into beaters. By breaking off all switching contacts and leaving only the anchor as well as the solenoid, I was left with an electromagnet that potentially could become a small traject beater. The DC resistance of the windings varied between 1k and 3k, so clearly the nominal working voltage must have been in the range 48V to 90V. Operated under these voltages, force and speed proved to be pretty limited. So I set up some experiments with much higher voltages (200V to 400V). When driven with small pulses with a duration in the order of 10ms, the coils started behaving the way regular beaters would do. The clicking noise was hard to avoid. So I got the idea to integrate it and set up a robotic project wherein the beaters would hit cooking pots and pans of different sizes. Thus the idea of the junk playing robot was born.



Only when integrated in the context of our M&M robot orchestra with its wealth of varied sensor systems allowing full interactivity, this automate will become a true robot. That's after all were its destination is to be sought.

Midi Mapping and implementation:


Midi channel: fixed to 1 (counting 0-15).

Note Off: Implemented for all notes in the range.

Note On: Implemented for notes in the range. Velo-byte is used for the stroke strength.

Controller 66: Robot on/off switch.


Technical specifications:

Design and construction: dr.Godfried-Willem Raes

Collaborators on the construction of this robot:

Music composed for <Potpan>:


Pictures taken during the construction in our workshop:



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Construction & Research Diary:

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Godfried-Willem Raes

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Last update: 2017-08-05 by Godfried-Willem Raes

The following information is not intended for the general public nor for composers wanting to make use of our <Pottepan> robot, but is essential for maintenance and servicing of the robot by our collaborators. It also might be usefull for people that want to undertake similar projects. Feedback is mostly welcomed.

Technical drawings, specs and data sheets:




Raes, Godfried-Willem, "Expression control in musical automates", 1977/2015,