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With a Little Help from my friends?

SparkyCal

Mar 11, 2020
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Hi guys. I don't know if you guys remember me. or if some of my friends are still here.

I started working on a simple Theramin project. For those of you whom don't know, a Theramin features an antenna. When your body gets close to it, it makes weird high pitched sounds. Bands like Led Zeppelin used it. Here it is in action:

I am using the following schematic: http://www.thereminworld.com/Forums/T/30562/lets-design-and-build-a-simple-analog-theremin?Page=0 ( the one that is Posted: 11/4/2014 10:49:53 PM)

I am stuck on the following:

1. L1, which appears to be a coil. Can Ki make a coil? If so, how would I make a suitable one for this circuit? If not,. where can I buy a suitable one?

2. It does not specify what kind of antenna to use. Any thoughts?

3. Just underneath the abbreviation for antenna ANT (far left on schematic), the word Cant appears. Any idea what that refers to?

4. Usually, the Theramin has an output (I am guessing a 1/4 inch male guitar plug, that you would run into an amplifier to hear the sound of the Theramin. I can't seem to find where connections for the 1/4 inch male plug. Any ideas?

Thanks for the advice.
 

Delta Prime

Jul 29, 2020
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I think I remember you.
Did you ever get that wort removed?
About the antenna the coil and the capacitor they are all specified in the thread.
"With a little help from my friends?"
That's the Beatles.
I didn't know led Zeppelin played with the Beatles.
I'll let the elders take care of this one. You will be disappointed though...it's not going to sound like led Zeppelin!
Jimmy Page used a variation of the theremin (pitch antenna only) during performances of "Whole Lotta Love" and "No Quarter".
That schematic won't do what you want it to do. Are you open to suggestions?
Jimmy page is wizard and lives in a castle; did you know that?

1697764838173.png
 
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kellys_eye

Jun 25, 2010
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L1 has a value of 0.5mH and can be made yourself or easily bought. It's value isn't that important. What you need are two oscillators of the same value and the 'value' is set by the LC (inductor/capacitance) values.

The antenna can be anything. Usually it's a telescopic antenna of 18-36 inches but can be a simple straight (or shaped) wire. The antenna will have its own inductance (nominally very, very, little) and some capacitance - the value of which depends on its surroundings i.e. 'you'.

'Cant' refers to the capacitance of the antenna - the value that is affected by your own physical presence and therefore varies the LC value and thus the oscillator frequency.

The schematic isn't a complete Theramin. It's only one small part. A Theramin consists of TWO oscillators, one a fixed value and one with a value that depends on the LC values - where changing the 'C' (by your presence) changes the oscillator frequency by some amount. Additional circuitry then detects the DIFFERENCE between the two frequencies and amplifies that result so you can hear it.

The LC values normally create a signal of many MHz as the change in 'C' is very small and will only make high frequency oscillators change sufficiently so you can detect the difference.

You need to get a complete schematic (guaranteed and proven working version) as the one you're looking at discusses the theoretical process and is not a 'solution'.
 
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ivak245

Jun 11, 2021
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Many years ago I built a theremin using the circuit from an Australian Silicon Chip magazine, It used a telescopic radio antenna and had an audio amp with outputs for your "proper" amp.
 

SparkyCal

Mar 11, 2020
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Thanks guys for all the advice. I’ll look for a better schematic, or maybe I’ll cave and buy one.
 

Delta Prime

Jul 29, 2020
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Thanks guys for all the advice. I’ll look for a better schematic, or maybe I’ll cave and buy one
Never!Cave in. Go with the flow. Adjusting swaying to the music. Just like a Thurman.
You can learn as you go they sell kits, all the components you'll need so you don't have to search everywhere for them.
It might peek your interest in physics. Check this out!


Screenshot_20231020_084800.jpg
 

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bertus

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Nov 8, 2019
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Hello Sparky,

Theremin world has a lot of schematics for a theremin:

I have also attached a PDF with a complete description on how to build a theremin.

Bertus
 

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kellys_eye

Jun 25, 2010
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Hello Sparky,

Theremin world has a lot of schematics for a theremin:

I have also attached a PDF with a complete description on how to build a theremin.

Bertus
Nice article but I suggest it might not be that easy to source the three-section RF chokes..... could be the 'killer' as far as constructing that version. Plenty of other versions in your other link of course.
 

Delta Prime

Jul 29, 2020
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Everybody sing. "I get by with the Little help from My Friends"!
 

AnalogKid

Jun 10, 2015
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If getting the RF circuits to work isn't working, an alternative is a Theramin based on optical, rather than RF sensing. Two photo-resistive cells, one varies the gain of an amplifier and the other varies the frequency of an oscillator. You wave you hands over the cells to block out variable amounts of ambient room light.

ak
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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Theramins are difficult instruments to play. One antenna controls the pitch and the other controls the volume. It takes some fancy hand movements to make the beast sound anything at all like real music.

I would like to obtain the skills and software to take images from a USB camera connected to my laptop and translate certain features of the image into musical notes. Imagine a conductor of an orchestra who can "play" any instrument just by waving his hands in front of a television camera. Might want to have the hands hold some sort of illuminated LEDs that the software can "see" and track the position of each hand. Imagine also an "air guitar" that actually makes guitar-like sounds. You wouldn't even have to know how to play a real guitar: just pretend to strum the strings and finger the frets and let the image processing software "fill in" whatever music is appropriate. Recording artists mime their hit songs when performing before a live audience, so why not mime the instruments too?
 

SparkyCal

Mar 11, 2020
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Hey guys and a special hello to my friend Bertus. Bertus. I printed that document for future reference. I did end up caving in because making a functional thermic was beyond my skill level. I purchased a Zip thermion for $137.00
 
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