My New Year gift to TW: A new theremin circuit

Posted: 10/12/2017 6:18:21 AM
melluxx

From: Finland

Joined: 10/3/2017

Hi everyone! I'm starting to do this as my school project, but I don't get it, from where I can order proper antenna? I mean, like what kind of antenna is it, RF, tube, which frequency (center/band)  etc? I'm so troubled when trying to find appropriate one i.e from digikey  . 

Posted: 10/12/2017 8:07:07 AM
xtheremin8

From: züriCH

Joined: 3/15/2014

hi melluxx,

don't worry too much about the antenna....Ø=6mm,L=~50cm...you need a simple one like this: antenna . you could easily salvage one from a broken radio or something.

 

Posted: 2/5/2018 4:47:35 PM
elkayem

Joined: 2/5/2018

Thierry, I just built your circuit design, and wow, this works better than I could have hoped!  My first theremin!  My 12 yo daughter and I had a lot of fun playing with it last night, as she repeatedly exclaimed "This is really cool!"   Thank you!

I've included a few photos below.  I included an LM386 amplifier and a small 2W speaker, and designed a 3D printed case for it.  I have discovered it works best when grounded, so have also added a grounding plug for use when not connected to an external amplifier (and grounded through the 1/4" connector shield). 

I do have one question though...  In your tuning instructions, you state that the coarse and fine tuning should be used to achieve "a pleasant field geometry and tone spacing".  I haven't played with a theremin before, so not sure what I should be looking for.  Is there a target frequency when, say, I am standing a meter away from the theremin?  And how many octaves higher should I expect when placing my hand a few inches from the antenna? 

Ok, some photos...

Photo 1

photo 2

photo 3

Posted: 2/12/2018 6:17:59 AM
randolphthegrey

Joined: 2/12/2018

"I've included a few photos below.  I included an LM386 amplifier and a small 2W speaker, and designed a 3D printed case for it.  I have discovered it works best when grounded, so have also added a grounding plug for use when not connected to an external amplifier (and grounded through the 1/4" connector shield)."

I really like the case that you designed. I am attempting to build some for a physics demo for school project. Is there some way I could get the design to print one off for myself?

Posted: 2/14/2018 4:35:25 PM
elkayem

Joined: 2/5/2018

"I really like the case that you designed. I am attempting to build some for a physics demo for school project. Is there some way I could get the design to print one off for myself?"

Sure Randolph!  I have posted the 3D printed case and amplifier schematic on Thingiverse:

https://www.thingiverse.com/thing:2783670

I've done my best to list all the specific parts needed to fit in the case.  Breadboard size, rocker button, and speaker diameter are all important.  I was able to find everything on Amazon and Mouser, except for the JFETs which I got off eBay for a reasonable price. 

This will make a great physics demo!  Turn your body into a human capacitor!  And the math showing the resonant frequencies of the two oscillators and beat frequency would make a great lesson. 

Let me know if you have any question on the construction of the case.

 

You must be logged in to post a reply. Please log in or register for a new account.