Sandwich Press Theremin

What you see was previously a very nice sandwich press. The thermostat failed, so opened it all up and attempted to order a replacement. It never came so, loathe to throw a nice metal case away, I thought I'd put one of my musical electronics projects inside it. The THEREMIN is a musical instrument that was invented in the 1920's by a lovely Russian man named Theremin. It's based on the effect that objects have on a radio frequency. You play it by moving your hand at varying distances to the aerial, the closer you get, the higher the note. Clever people can play melodies on them. I'm not one of them! It's a common sound effect from 1950's science fiction movies. 

In my research I have found that there is a mistake in the schematic. Pin 10 on IC 4069 should be pin 9. Pin 10 is an output pin so should never be attached to the positive power! As you can see I corrected the diagram above. The original article is here:https://manualzz.com/doc/1069739/the-555 (navigate to page 28/32 of the magazine).

Interestingly the printed circuit board diagram connects to pin 9. Also the text refers to "connecting antenna to pin 5 (of 4046 IC)" but it should be pin 6, as shown in the schematic. It's an interesting article. The most important thing is that a metal case, and allowing warm up time gives better performance.

I fashioned the aerial from one I got from an old radio and put it into a metal jack socket, pinching the innards around the aerial. and then heat-shrink inside. I may have tried to solder it a bit. Then it just plugs into the top.

It works OK for a bit of fun. I just wanted it for a bit of recording. Mixed into my songs with lots of reverb and echo it's fine. I'm into making weird noises rather than playing melodies with it. And this circuit is cheap and simple with easy to obtain parts.

If you want a proper theremin to play melodies that's nice and stable then I'd say make a better one if you are experienced in electronics. Proper theremins are a lot more complicated! There are kits and pcbs around if you look. Or buy a Moog one! But I'm happy with $20 spent and making a noise. 

Good luck! Stay safe.😎