Building an easy theremin

Posted: 12/13/2016 8:55:54 AM
sleepycc

Joined: 8/25/2016

This post is to build a one antena theremin (no optical unit) , battery powered; which coincidentaly has a fair resemblance to a green pig from the "Angry birds" videogame. A theremin is an electronic instrument that poduces sound waves without physicaly touching it. I wanted to build it for friend and it seemed an easy electronic project.
I got the schematics from a web page (in spanish, but the pictures are easy to read)

A small caveat, the resistor marked as 1.07 kOhms is a mistake. Its real value is 1.7 kOhms.

Step 1: B.O.M.

I used the following materials

1 x potentiometer 5K linear

1 x potentiometer 100K linear

------ceramic capacitors--------------

2 x 27 pf

3 x 15 pf

4 x 100 nf

2 x 4,7 nf

3 x 10 nf

2 x 68 pf

------1/4 W resistances------------

2 x 470 Ohm

2 x 100 kOhm

2 x 22 kOhm

2 x 4,1k or 3,9 k

1 x 3,3 megaOhm

2 x 1 megaOhm

1 x 47 kOhm

1 x 1,7 kOhm

-------transistors-----------------------

2 x BC546

1 x BC558 (or BC557)

------chokes------------

2 x 100 microhenrys

--------miscellaneous-------------------

1 - telescopic antenna

1 x 9-volt battery holder (recycled from a dead 9-volts battery)

1 x plastics casing (recycled from a Sogo orange juicer )

1 x On/off switch (I got mine from a scavenged computer)

1 x perfboard

1 x audio jack connector

1 x solder

1 x soldering iron

1 x shielded wire (less than 50 cms)

Step 2: Schematic lay-out

I have taken the liberty to correct the value of the 1.07 k to 1.7 k in the drawing. The red squares are removed traces to avoid shortcircuiting. Just cut the copper using a blade or a multi tool. Confirm it with tea continuity function in a multimeter.
Step 3: Prepare the case
I had a juicer laying around that we never use. So I emptied its interior and cut off a plastic stem it had on top. Avoid using metallic casings, they interfere in the signal.
Step 4: Solder components into board
Step 5: Place pots and switch
I drilled the holes for the pots (hold by nuts), switch and jack audio (hold by glue).
Step 6: Final touches
That´s it. Hot Glue the board to the case. Solder all connections and make sure that anything is loose. Connect your theremin to your computer speakers or stereo and off you go !.
 

 

Posted: 12/13/2016 1:37:43 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Hi sleepycc,

What's the url you got the schematic from?  From a quick glance and without sketching it out it looks rather like the Thierrymin, but using bipolar transistors rather than FETs.

Metallic cases are OK for analog Theremins if you make allowances for them and keep the antenna far enough away.  I notice you use some metallic tape inside, which is kinda the same thing.

Posted: 12/13/2016 6:17:05 PM
ILYA

From: Theremin Motherland

Joined: 11/13/2005

"Metallic cases are OK..."

Plus, if you're going to hold the device by hand ala Takeuchi's matryonim , this will significantly improve the response.

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