Advice Needed About Building A Theremin

Hi All,

I'm planning on building a theremin for a high school physics project. I have talked to my teacher about parts, and getting those shouldn't be much of a problem.
I'd like to be able to build a theremin that has an antenna for both volume and pitch. I don't want to let complexity be a problem, so I'm open to lots of ideas. However, I'd like to know the approximate cost of the different circuits. Speaking of circuits, I don't have any idea about which circuit schematic to follow. I'm shooting for something that resembles the Moog Etherwave Standard theremin. I'd like to be able to use actual antennae instead of a substitute like metal plates.
I don't really know where to start, so advice about different circuits and other info is appreciated.

Here are a few other general questions I have:
Will the theremin I build need to have knobs like the Moog Etherwave Standard has (pitch knob), or can it work just fine without them?
Does the material of the encasing affect performance? If so, what are some standard materials?
I'd like to have a speaker built into the box, as well as an output for a PA system or headphone jack. Are these possible?
What power source do I use to power the theremin itself? Would I need an additional power source if I added in a speaker?
How much open space is needed for operating a theremin?

Thanks a ton for any feedback,
Dan

Hi Dan.

What a lot of questions.

>I'd like to be able to build a theremin that has an antenna for both volume and pitch.
>I don't want to let complexity be a problem, so I'm open to lots of ideas.

How much experience do you have building circuits? (I have none, by the way, but I've been hanging around TW a while and I picked up a thing or two.) A decent two-stick is a major project - there's a lot of tweaking and fiddling about after you've soldered all the bits together, For a science project the point of a theremin is to demonstrate heterodyning, beats and body capacitance. A two stick theremin is basically only two one-stick theremins with a bit of extra circuitry to turn frequency into amplitude on one of them.

It's probably a good idea to cut your teeth on a simpler device first. Prof. Theremin did. His first devices used a pitch antenna, volume pedal and cut-off switch.


>Will the theremin I build need to have knobs like the Moog Etherwave Standard has (pitch knob)?

It needs them.


>Does the material of the encasing affect performance? If so, what are some standard materials?

Yes - the circuit will have to be tweaked to take the casing into account. Wood. Plastic.


>I'd like to have a speaker built into the box, as well as an output for a PA system or headphone jack. Are these possible?

Yes.

>What power source do I use to power the theremin itself? Would I need an additional power source if I added in a speaker?

Those depend on the particular circuit you are building, and how much volume you want.


>How much open space is needed for operating a theremin?

I've used my etherwave in some pretty confined spaces - stationary objects are not really a problem - that is one of the reasons for the knobs on the front - to adjust for the player's body mass and other nearby objects. You need clear space within the playing radius - say two feet around the antennas. Moving objects are more of a nuisance - I don't welcome people within a six foot radius of my instrument when I am playing.

Thanks for the feedback...

What do you mean when you say tweaking the circuitry? Do you mean adjusting the knobs, or changing the distance between the different components?

I don't have much experience with circuitry (essentially none), but I'm very willing to learn and try. My physics teacher used to be an electrical engineer, so I could get a considerable amount of guidance from him (obviously he wouldn't be doing the project for me).

I've looked at the design locatated at http://emusician.com/diy/em_theremin/ (The one that Robert Moog explains how to build in a magazine article.) The directions seem clear, and I feel like I would be able to figure out the circuitry with the help of my teacher.

Does anyone have any idea how much building the theremin from the above link cost?

I don't think that I want the internal speakers anymore, just an output for a PA system or something similar.

Building the case won't be any problem, because I have a lot of wood working experience, and my school has and industrial arts shop where I can easily bend the antennas and aluminium covering.

I really want to give the two antenna theremin a try, and I have ample time (not due until April). I understand that the construction is complicated, but I've done other projects without much experience and they came out nicely. I really don't want to have to settle for a simple theremin.

Thanks again!

By [i]tweaking[/i] I mean the sections entitled "Checking It Out" and "Tuning" in the Bob Moog article you mentioned.

[i]I've looked at the design locatated at http://emusician.com/diy/em_theremin/ (The one that Robert Moog explains how to build in a magazine article.) The directions seem clear, and I feel like I would be able to figure out the circuitry with the help of my teacher.
[/i]

The EM Theremin is a very good place to start.
Start with a piece of graph paper with 0.1" grid
and layout all of your components. Plan out the
wiring. After your graph paper layout is complete build the pitch circuit first. After the pitch circuit is complete add the volume circuit.

Assembly the circuit on Vector 169P84WE board
and use Vector T42-1 and K24A pins for the connections.

[i]Does anyone have any idea how much building the theremin from the above link cost? [/i]

The only expensive parts are the inductors
and the LM13600. Try finding the parts in
Digikey and then use findchips to get the
best prices.

I have some general procuremnent notes at
http://www.luciani.org/getting-it-done/getting-it-done-index.html

A picture of my SMD version of the EM pitch
oscillator + amplifier is at
http://www.luciani.org/eng-notes/ee-notes/ee-notes-index.html

(* jcl *)

Thanks for all the help...

The article on building the EM theremin says that I should use a Radioshack 10"x4" prototyping board- is there a reason to go with the Vector one? From what I've seen, the vector board is larger, and I'm not sure if that would fit the case design...?




In terms of order of construction, where do the amplifier and oscillator and other circuits go?

Thanks again

[i]
The article on building the EM theremin says that I should use a Radioshack 10"x4" prototyping board- is there a reason to go with the Vector one? From what I've seen, the vector board is larger, and I'm not sure if that would fit the case design...?
[/i]
The Vector board is glass-epoxy prototyping board and will not crack like a paper-epoxy board. I am not sure what material the RadioShack board is
made of. The cheaper boards are paper. It is
depressing when you finish your masterpiece and
end up cracking the board :-(

To cut the board I usually just score it along
a row of holes with an X-acto knife and break
it over the edge of a table.

[i]
In terms of order of construction, where do the amplifier and oscillator and other circuits go?
[/i]

You should be able to make your physical layout
very similar to the schematic layout. If you
look at my PCB you can see how I arranged the
sections. Each section has a silkscreen label
that should be legible.

Looking at the bottom image at
http://www.luciani.org/eng-notes/ee-notes/ee-notes-index.html

On the top you can see L1 which is one of
the four series JWMiller inductors that connect to the antenna. Below that is the variable
oscillator. Below that is the amplifier on the left and the detector on the right. Below that
is the pitch adjust on the left and the fixed
oscillator on the right. Below that is a
+-5V switching requlator. I changed the circuit
to use a +-5V supply rather than the +-12V supply. You should stick with the +-12V supply
in your schematic.

(* jcl *)

Hi,

Some more questions...

I'll go ahead and use the Vector circuit board, but since it's big enough to fit all the circuitry on it, will it still be necessary to use separate circuit boards for the antenna circuits (would there be a problem with distance between circuits or something like that)?

I've been using Findchips to find the different components, but some are hard to find- I haven't been able to find the LM13600N dual operational transcondance amplifier anywhere where I can order it (Digikey lists it, but I can't order it). I also can't find any of the capacitors that are polypropylene, polystyrene, or polyester. Is there a substitute? The J.W. Miller inductors are offered at Mouser, but they are out of stock, and one of them isn't expected to be in stock until 2012. The Toko inductors also aren't currently available or able to be ordered at Digikey. Are there any substitutes for these inductors? I also haven't been able to find the DPA120020-P1-SZ 12 to 15 VAC transformer- Digikey doesn't have it availible for ordering. I'm wondering if there are any subsitutes or other makers or this...? The pententiometers have also been something that I couldn't find- any ideas? I couldn't find the 1.8 M Ohm resistors either.

In addition to not being able to find several parts, I don't really know what is meant by the SPST miniature power switch, the two phone jack connectors, and the 16 pin IC socket. There are far to many items that come up in a Mouser search to know which ones to get.

I also have some general questons about capacitors and resistors: Some of the capacitors in the parts list don't have tolerance percentages, so does the tolerance not matter at all? For several of the resistors, the wattage is 1/4W 1/8W DUAL- is that OK, or do I need strictly 1/4W resistors?


Thanks to those who reply!

[i]
I'll go ahead and use the Vector circuit board, but since it's big enough to fit all the circuitry on it, will it still be necessary to
use separate circuit boards for the antenna circuits (would there be a problem with distance between circuits or something like that)?
[/i]

Probably not. You could always cut the Vector, with some tin-skips, after it is complete. You would just have to re-wire the antenna circuit.

[i] I've been using Findchips to find the different components, but some are hard to find- I haven't been able to find the LM13600N dual
operational transcondance amplifier anywhere where I can order it (Digikey lists it, but I can't order it). I also can't find any of the
capacitors that are polypropylene, polystyrene, or polyester. Is there a substitute? The J.W. Miller inductors are offered at Mouser, but
they are out of stock, and one of them isn't expected to be in stock until 2012. The Toko inductors also aren't currently available or able
to be ordered at Digikey. Are there any substitutes for these inductors? I also haven't been able to find the DPA120020-P1-SZ 12 to
15 VAC transformer- Digikey doesn't have it availible for ordering. I'm wondering if there are any subsitutes or other makers or
this...? The pententiometers have also been something that I couldn't find- any ideas? I couldn't find the 1.8 M Ohm resistors either. [/i]

The LM13700 may work.

You should be able to find the polypropylene, polystyrene and polyester caps in Digikey. You also try polycarbonate. For small value caps NPO or COG ceramics should work.

I believe JWMiller may be part of Bourns now. Try the Bourns website.

See if Coilcraft has any inductors comparable to the Toko inductors.


[i]
In addition to not being able to find several parts, I don't really know what is meant by the SPST miniature power switch, the two phone
jack connectors, and the 16 pin IC socket. There are far to many items that come up in a Mouser search to know which ones to get.
[/i]

The Mouser search is useless. Use the Digikey search and then FindChips to check prices. Call Mouser and Digikey and have them send you a printed catalog. Except for semiconductors, R's, L's and C's it is usually quicker to use the catalog.

[i]
I also have some general questons about capacitors and resistors: Some of the capacitors in the parts list don't have tolerance percentages, so does the tolerance not matter at all?
[/i]

Tolerance matters depending on the application. For power supplies your capacitors can be 20% tolerance. For most other circuits you should
go for 5%. For common value 1/4W and 1/8W resistors I would only buy 1% since the cost difference between and 1% and 5% is small.

(* jcl *)

Hi,

I've been able to find everything except poly capacitors, TOKO inductors, and power transformer.

Would the TR12500 from provide me with 12 to 15 VAC, and be able to be plugged into a wall?

As far as tolerance for capacitors go, would a 1% tolerance work for a part that says I need 5%. In other words, is the tolerance ok as long as it's not more than what's listed in the plans? Are there any substitutes for the poly capacitors shown in the plans, or is there another material that would work?

The potentiometers listed in the plans cost about 10$ each, with a power rating of 2 watts. Will 1/2 watt potentiometers from RadioShack work, or do I need to go with the more expensive Clarostats?

There is no place I have been able to find the listed TOKO inductors (I found the J.W. Miller ones). I've looked for similar inductors at coilcraft and other places, but I don't know how similar they need to be. The TOKO 154ANS-T1019Z variable inductor's specs are - 68.0uH±10%, 60-Q min, 2.52MHz. The TOKO RWRS-T1015Z variable inductor's specs are - 100uH±10%, 100-Q min, 796 KHz. How close would the specs of a similar inductor have to be? Does anyone know of any subsitutes?

Also, how do I know if the 16-Pin DIP IC socket will fit my LM13600 DIP? What type of socket fits the LM13600?

Thanks,
Dan