How To Build An Optical Theremin

What is a theremin? It is an instrument that can be played without being touched. Traditional theremins use antennas and oscillators to sense a person's hand and generate a tone. Ours will use light instead of this, it is not an actual theremin, it just uses similar principles. As a side note, this is my first instructable, so please be nice.

Here is a video of a real thermin:

This is where I learned how to do this:
The original optical theremin

Step 1 Gather Materials!

This needs very few parts, I made mine for under $20.

Here is what you need:

Two phototransistors
One TLC555 timer IC
One .047 uF capacitor
One 100 uF capacitor
One 1 megohm resistor
One 10k ohm resistor
A battery pack that holds 4 AA batteries
Some wire
A breadboard
A small speaker

Tools:
A wire stripper

Comments

[slinky773]

Is it absolutely necessary to use a radial-lead capacitor for the 100 uF, or is it OK to use an axial capacitor? I know that you're not exactly supposed to use an axial capacitor for this, but is it OK to use an axial capacitor?

[shakespeare1212]

Very interesting, thanks for posting. I made a Theremin myself using a Wii Interactive whiteboard, and a free PC program. http://www.youtube.com/watch?v=QSCPQ6sHpWA

[GHOSTROSSI46]

please tell me that how the circuit works ???

[trubshac]

We have just built this and it works great, although we did change a few things:  We didn't have any opto transistors but we did have some infra-red sensors, so we used these instead.  We added an infrared LED via a 100R series resistor, so now when you move your hand, you are changing the amount of infra-red that is reflected back to the sensors.  We changed C1 to 10nF, R2 to 2M2 (because that's the nearest we'd got), C2 to 47uF (for the same reason) and R1 to 33K.  All values were found by experimentation.  We also added a potentiometer on to the output to form a volume control, and powered the whole circuit for 3v instead of 6v. 
I noticed from the comments that some people had disappointing results - assuming that they built the circuit correctly, this may well be because they used different spec opto transistors, and may therefore need to change C1 and/or R1 to compensate - I suggest experimentation with different values like we did.

[jwoo2023]

you could have inserted a photoresistor so you can controll the volume like a real theremin

[zoltzerino]

Fart joke!

But seriously, my mate owes you - he used this a couple of years ago in a GCSE research project - NICE ONE!

ZZZZ

[irtentiapen]

Is it possible to exchange Q1 & Q2 for a resistor?
so you could connect it to a sort kind of string (witch has a very low resistance).
(sorry for my poor english)

[bibbibbib]

where did you get your parts

[mwagner63]

this is what sheldon used in the big bang theory

[electrosam]

Well, as per my knowledge, thats not Photo Transistor, its Photo Diode. Probably IR Detector Diode.

[BassGeek]

I found it at Radioshack as a photo transistor

[BassGeek]

Now I want to add a 1/4 inch jack and a volume pot... How do it do it??

[ocarina guy]

Sounds kinda like a chainsaw, but I'll still make it for the fun of it! Nice job!

[theunexpector]

Sounds like a taco bell night!! Just kidding, the idea of the light is clever, is it possible to get a higher pitch?

[Zibodiz]

hmmm... it sounds like it would make the perfect 'creaky door' sound effect!

[oweng4000]

will 9v work?

[diegolpe]

I don't think so. As far as I know the voltage range of the 555 chip is 5 volts 9 volts might blow your chio away.

[ash303]

I built one using the exact same circuit diagram, using a 9v battery, and it works just fine. Great Instructable!

[moshee]

The range of the 555 is from 5 volts to 18 volts, if I remember correctly.

[trubshac]

Yes 9v should work fine.

[i like diy]

how can I get a lower frequency ??? my one makes a verry high loud noice. :( not like in your video...

[omnibot]

Oopa .. I meant R1 (my bad). Also ahnkels suggestion is good to use a pot rather than a fixed resistor but use a linear potentiometer rather than a nonlinear volume.

[omnibot]

Increase the value of R2

[ahnakel]

why not just add a volume potentiometer for the speaker out?

[jwoo2023]

or a photoresistor like a REAL theremin

[htaeh]

Very awesome. Thanks.

[ninjin]

Mine turned out great, annoying, but great! thanks for this 'ible!

[BassGeek]

 Mine does the exact opposite of what its supposed to do...

[Ankeladden]

which capacitor do you youse 0.047 uf?? I'm going to make one

[BassGeek]

 Do you mean like an electrolytic, monolithic, tantalum, etc?

[sacred]

Yeah, the Radio Shack number is 272-1068

[TXTCLA55]

Question! you mean the 555 timer IC right?

[trubshac]

Yes, it's a 555 timer IC.  The 7555 timer should also work fine.

[thestyrofoampeanut]

 i made it and the batteries burned out the timer ic
hours of work for a burned ic.....
i wanna punch a wall

[Jodex]

Very cool instructable. Actually I'm going to make this the day after tomorrow=) When I'm goin' to buy couple of 555 and those transistors...

[Jodex]

Made and this is veeeeeeeeery cool!! Thanks a lot for this instructable. Favourited=D

[k.sowmyan]

hey this is cool ...... but may i know the purpose of each and every component used !! example 1. does the photo transistor conduct when blocked from light or illuminated to light ? 2.what does the 555 ic do in this project ? 3. what does the 47K and the 100 micro farad capacitor do ? 4. instead of getting noise signal at the output speaker what should i do to get some music ? 5. how can i implement this circuit in the musical instruments say for example a keyboard ? the project was awesome...kindly can u reply to these questions ...my e mail id is [e-mail]

[ridethetiger1983]

Brian Wilson eat your heart out! This sounds like an electrice fart machine. Nice try though. Don't give up the day job fella.

[thestyrofoampeanut]

thats totally what i thought! fart machine!

[technologysucks]

So I got the RS Optical Theremin working, but for some reason my volume phototransistor burns out or something after a day. It still reacts to the light on the pitch phototransistor, but it is not as loud as it is the first day a built it because of that cell. I built two and this happened both times. Any thoughts as to why this may be happening? Thanks