Easy Theremin

This instructable 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 this web page (in spanish, but the pictures are easy to read)

http://www.pisotones.com/Theremin/Theremini.htm

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 !.

Comments

[WesleyC57]

1) Use a 12v source, it sounds better;


2) Change the 5k potentiometer for 1k potentiometer, it improves the tuning;


3) Try to use only a small wire without the antenna;


4) If you want a volume control for the left hand you can use two LDR connected in parallel in the sound output between the ground and the 100nf capacitor;


5) If possible, solder the pots directly on the plate to avoid wires;


6) Grounding the potentiometer housing is very important to avoid noise;


7) Avoid metal box.

Videos on my instagram: @electrovnil
Hope this helps! Thanks

[iam_thezombiewolf]

The schematic that "psst" provided it's completely wrong. If you pay attention, it has around 3/4 4k7 resistors that are not really in the diagram that is show in the instructable above.

Hope it helps

[WesleyC57]

I followed the psst scheme and it worked.

[Unit-ES55111]

Were did you get all the materials?

[PrometheusX1]

Do I HAVE to use ceramic nonpolarized capacitors or will electrolytic polarized capacitors work?

[Roboticslab]

Hello everyone! I have tried to make this but it's not working for me. Can someone please tell me if there is a mistake in my circuit? And if anyone has some tips to help me get a proper sound out of it, that would be helpful too!

[NickM135]

Hi in your video (the one with the frog), you had another schematic could you post that? it included a LM386 amp. many thanks

[willem112]

Don't you need a coil for this

[pje8268]

Which potentiometer goes to which knob. It's not specified.

[alexiscontrol]

i've built it and it works, but i think it have some issues:
-low signal (compared to a guitar), it's that normal?
-a horrible groundy noise: it increase when i touch the chassis jack, and decrease when i touch the metal cover the plug of the cable...
-it doesn't sound when i'm not touching the "tune" pot.

it seems like a ground trouble... what do you think? i normally built electronic projects in metal cases, so i don't know how to ground this thing...

Thank you a lot, and sorry for my argentinian english

[bcaccam]

Used wrong account, sorry! Please respond to this account so I'll get notified. ( I no longer have the email account to thenuclearlemons)

[pje8268]

Where did you find a 3.3 megaOhm resistor?

[XLY]

I agree with you about the grounding. Start checking the case of the tune pot. I recommend you to use aluminium foil to cover some spots as ground.

[thenuclearlemons]

Hey, do you mind posting pictures of your layout? You're getting more success than I am right now XD. Also, in Step 5, he lets the metal casing of one of the pots, which may be in contact with the antenna. That might solve your problem with not touching the tone pot.

[pje8268]

I can't find a 3.3 megaOhm resistor. Any help?

[Xyiro]

Hey guys, could someone please tell me where the audio jack goes because the diagram/pictures provided are a bit confusing.

Thanks

[dgēllērēr]

the "hot" signal goes the the "out" at the middle of the volume pot. the other wire from the jack goes to the ground.

[Xyiro]

Does anyone know how to wire to the audio jack. Is there only one wire that connects to the jack? If so where? Please help.

[dgēllērēr]

the other wire goes to the ground.

[zanscath]

I've just finished building this and I can confirm the instructions are correct. I've managed to do this (almost - I had two traces touching through a small stream of solder and I couldn't see this, it took me a while to figure) on the first try.

I used BC546 and BC547 transistors and it works fine.

But it's really tricky positioning the pots and antenna so that everything works correctly. Grounding is also very important.