Fake thermins and related - getting students interested in the technology

It seems like this is as good a forum as any to bring this up. I scanned the others and haven't found any conversations related to my first question. I'm certain that there are none for my second...

So first, I am a professor at the University of New Hampshire and I teach a system design class where the students build a final project of their choice with a microcontroller or Raspberry Pi as the center. We do a lab with ultrasonics, and invariably that makes at least one student think of theremins. I had access (pre-COVID) to one i could borrow but it seemed like it was time to buy my own to bring into class for inspiration. So i now own a pretty Etherwave with extended pitch mods.  Once they play with it for a while, those that are really captivated by it will then build a fake one on the Raspberry Pi with ultrasonic sensors for pitch and volume. The technical problem to solve is that the Pi can't generate pitches and change them smoothly. I've solved that problem by finding a $10 Amazon function generator with pots that can be replaced by digital pots...  It's been used once and it actually worked pretty well. I'd be looking for anyone who has experience with this to share notes.  Sadly, the students didn't work with the thing while writing the code for it to actually learn how to play anything. I will be sure to get a video of it next time a group builds one. It would be a fun test to then have an experienced player see if the thing is playable---  anyone in Southern NH??

Second question that came up is building a robot to *play* a theremin. We know it works by coupling the body capacitance into the circuit to affect the pitch. Has anyone ever tried to find a human analogue that can affect the pitch and be moved by a robot?  Specifically, if I attach a pack of hotdogs to a stick and have a robot move it closer to and farther from the antenna, can it play a song?  Obviously I'm going to try that myself, but I'd love to chat with anyone who has looked at this.  The student asked about making a MIDI instrument out of my new Etherwave with some servo motors and a pot roast.  Has this been done?

When my student builds a robot that plays music on the Etherwave, will they be the first?

Howard

A Raspberry Pi used to build a theremin, that's already been made before.

https://www.gaudi.ch/OpenTheremin/

As far as I know, playing a theremin with a pack of hotdogs has never been done before.
I would suggest to use the sausages only (without the bread) as fingers for the robot's arms.
However, I strongly recommend to connect all sausages to ground. Otherwise, their movement wouldhave little effect on the theremin.

Connecting each sausage-finger separately to ground through switches driven by the digital outputs of the Raspberry Pi would probably be interesting.
Robot's arm movements would be used to perform glissandos whereas very fast note changes would be made using sausage-fingers connections with no need to move the fingers.

That would avoid the hassle of trying to implement Carolina Eyck's fingering technique into the Raspberry Pi program.

I'm really looking forward to watch the first video of a sausage fingered robot playing our beloved instrument !

Thanks Andre-

The Open Theremin is a capacitive shield solution that connects to an Arduino.  I have one of those but it doesn't go very far in convincing students that this is a really cool instrument. It is an impressive hack but it kind of sounds like one.  The tech we're using for our lab is ultrasonic (this is a decent video on the sensor - https://www.youtube.com/watch?v=ZejQOX69K5M). There isn't any possibility of fine control here, but it is a good project for learning about digital pots, signal conditioning and software data filtering.

I love the idea of making the sausages individually grounded and switchable. Yes, that would be a really handy way of changing notes quickly in addition to having the ability to move them in relation to the antenna.  Fortunately it won't hurt the theremin to try it out.  If the Etherwave inspires them to either build the fake one or the robot that plays a real one, I will be certain to post videos.  In my searching the internet I'm finding no mention at all of using grillable lunch meat to make music.

Well, the sound of lunch meat grilling on a barbecue is already music when you are hungry !

That's certainly true. I'll be talking with the student team next week and we'll see what they think. Whether they're interested or not, the robot with meat fingers sounds fun to do. 

Welcome baldy672!  You might want to check out ILYA's excellent work here:

http://www.thereminworld.com/forums/T/31505?post=211223#211223

This might interest you too (RC oscillator with gamma function linearization):

https://www.linusakesson.net/hardware/theremin/

A vegan-friendly alternative to the saugages: stuff rubber gloves with cottonwool and saturate with salt water and connect earthing wires to them. Actually when the robot is going to have metal arms (and fingers) to play the antennas, they just need to be grounded, nothing 'meaty' required. The body/arms/fingers of the thereminsts are the moveable parts of 2 variable capacitors, the variable capacitor the volume hand and de expression loop form modulates the amplitude of the poutput signal, the pitch hand and rod form the variable capacitor that modulates the frequency. The body/hand has sufficient capacitive coupling to earth (for the RF frequencies involved) to have the hands act as earth grouded variable capacitor plates withi the circuit.