## Introduction: 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 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 !.

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

Were did you get all the materials?

I made this and it does work, and I am making another one and will then show how it was done. One thing I can tell everyone is that you need a descent amp, simple PC speakers won't likely work, and neither will unpowered speakers or headphones. I was running it through my Pioneer sx 737 which is an old 70's receiver. A guitar amp would work well and I tested mine on that too. Grounding is also a big thing. I got it to work fairly clean with the proper grounding, I had almost no buzzing at all, unless I cranked it up really loud.

Also, I put it in a cookie tin (but ate all the cookies first :P). That might help protect it from interference.

I will post a video of it soon with some explanation of how I got it to work.

I will post a video soon showing what I did, and how it worked out.

Hey Maarkaus, could you tell me how you wired the audio jack if you don't mind. The diagram only shows one "out" cable to the jack. What about the other 2 terminals in the jack?? Where do they go.

Thanks!

Suprised it took so long to for anyone to clarify this . Those output leads are connected to a variable resistor the output is from the wiper the other two are the outside leads of the variable resistor. Connect the out put to center conductor of a shielded cable and ground the shield , the center is the audio out . Hope this helps.

Yes for sure Xyiro,

What I did was connect the stray lead from the Tono to be the ground for the jack. It worked well for me and here is the video I put on Youtube:

I am going to make it again, as this Theremin I gave to my brother. Once I make it again, I will try different wiring methods including connecting the ground of the Jack to the ground of he board, and so on.

One thing I can tell you is that I checked the original article in Spanish (see the link that XLY included above, and the Cap going to the antannae can be changed all the way up to 68p. I did that too and it worked for me.

Thanks a lot Markaus!! I made this a while back and it failed horribly..Maybe I'll make a new one now that I know more about where the leads go!

I wish I could add this to my original comment, instead of replying to myself, as that seems an odd thing to do.

Due to the fact that many have requested a sample of what the theremin might sound like here is a link to a video I made:

Everyone's theremin may sound different depending on variances. For example, I changed the cap going to the antennae to be 68p instead of 15 as I was not getting a resuly with 15p. This was mentioned as a possible solution on the original site that this article links to.

If you are getting no sound and you are grounded and all your connections seem good, etc. then try changing that. it may help.

I will try other expierments and update here,and on my video link.

Cheers.

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

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!

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

Don't you need a coil for this

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

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

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

Where did you find a 3.3 megaOhm resistor?

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.

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.

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

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

Thanks

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

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.

the other wire goes to the ground.

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.

dude can u share some photos or material.

can you explain how does the circuit works

guys can somebody please explain me how the circuit works .

For all of you that have no sound , as you can see there are two stages of BC546 almost identically , the difference is the tone pot to adjust the frecuency of oscillation , the antena goes from the stage with no pot between the 68pF cap and 1M resistor way to BC558 stage , after hours of desperation of getting no sound, Ive tried to put the antenna on the other stage , the one with the pot , in the same spot of the stage, between the 68pF cap and the 1M resistor, and I got sound at the first, as far as I understand a bit the circuit , if you adjust the oscillation Frec with the pot , and the tone with the antenna and your hand , the propper thing is to put antenna and pot in the same stage of oscillation, hope it can help anyone !

Does anyone know what the frequency of the oscillators is supposed to be?

I've built this, but can't get any sound.

Here, found @http://www.pisotones.com/Theremin/imgs/FMK/Esquema-Theremin_papel.jpg

what's the total cost for this?

one more thing...

I found it hummed like mad and the shaft of the tone pot could act like a pitch antenna ar certain settings. Works better if you properly ground the pots - solder a wire between each of the back casings, and then on to the negative rail.

Cased this in a mobile phone box. To my surprise it worked first time - surprise not because of the instructions but because I've never done any electronics before. Hooked up to my Blackstar guitar amp.

What kind of choke do I need for this? Common mode choke?

Easier that that

http://es.rs-online.com/web/p/inductores-para-pcb/1911147/

How is the battery only on one point?

Because in electrical diagrams ground is of common appearance it is marked as the three paralel lines that youn see connected to E1. That is your negative or 0V level. The positive of yourpower supply is the +9V that are connected to A13.

Hello. Thanks for the hard job. My instruction in electronics is very simple, and there´s problem to me to resolve the battery and the audio output schema. Can anyone tell where are the positive and negative (battery, of course) solded? and the audio output? Thanks.

Anybody have a better detailed schematic? Perhaps a non breadboard schematic would be helpful. Thanks a bunch!

I'm thinking about doing a workshop for kids to build these, where I would pre-assembled most of the parts. Could somebody verify if this works? Thank you!

Hello FinleyS, I would not go for this circuit (shame on me). I would recommend you to try a drawdio, atari punk console or an optical theremin. Cheers.

I was considering using this kit,

but the drawdio looks very cool.

Thank you.

Not so far

Did anyone actually build a working one? I've tried it twice and no result. Does it matter if I use a 22pf cap instead of a 27?

There should not be a significant difference but people has found difficulties building it. I can explain why, maybe it is with the coils or the ambient conditions.

Are there any sound clips on the web of this model?

:)

Rebuilt it and still no luck. All I can get is a slight buzzing when I touch the antenna. I'm adding some pictures of my build if someone can be bothered to take a look.

Could anyone post the transistor EBC voltages on their working build?

I built one a few days ago based on the veroboard layout, here are the voltages. BC546(Near tone knob) E: 1v B: 1.50v C: 9.09v

BC558 E: 9.16v B: 8.17v C: 5.21v

BC546 E: 0.82v B:1.27v C: 9.11v

The circuit works, I haven't shielded mine yet so there is sometimes interference and the output is low. I have to position the pots and antenna sometimes to get better signal. Also, while touching and adjusting the tone knob I get loud thereminish sounds, it works though, I still have to mount it in an enclosure.

148,201views

219favorites

25
More by XLY: