Theremin Schematic & Layout

[Ben Lyman]

Can I get some eyes on this. It's a Radio Shack optical theremin kit that I am making for a gift. I want to change it a bit and I have it breadboarded in the way I want.
1st the original schematic:

Here's my attempt to write it the way I want to do it:

Here's my attempt at a layout:

I see I have mis-labeled my switches but I think you get the idea. They are push button momentary on switches, one of them turns the power on thru a 100r and the other jumpers the 100r creating siren-like intervals. I want to make my own board for this and put the switches and photo resistor on the bottom of the board which then (hopefully) will line up with 3 holes in the tin tea can wherein lie the battery and speaker.
Look OK to you?
BTW, how could I go about modifying this so that, instead of going to an 8ohm speaker, would go into my guitar FX/amps?
Thanks! and sorry about the giant pics... Tinypic? not so tiny...

[GiovannyS10]

Nice! I am sorry for cant help you, but i want to build a theremin soon, so i liked so much your post. 

[duck_arse]

add a voltage divider in place of the speaker (but following the cap). 68k over 22k? somewhere to start. or add a real volume control.

looks ok to me, but I'd swap one of the 100nF supply bypass for 100uF.

[amptramp]

Lots of design ideas here:

http://www.theremin.us/

[Ben Lyman]

Nice! I am sorry for cant help you, but i want to build a theremin soon, so i liked so much your post. 

No need to apologize, thanks for the thread bump! 

Lots of design ideas here:

http://www.theremin.us/

Cool, thanks. I'll browse that later when I have more time.  It looks like probably only real theremins but I am making a pocket theremin that sounds more like an Atari Punk Console.

add a voltage divider in place of the speaker (but following the cap). 68k over 22k? somewhere to start. or add a real volume control.

looks ok to me, but I'd swap one of the 100nF supply bypass for 100uF.

Thanks Duck, when I make one for myself I will do just that, add a volume knob if it's that simple then, great! I guess I would also go as far as adding all the usual power filtering stuff if I were making something more serious to use with my pedals & amps. Maybe some sort of built-in A/B switch so I could keep my guitar plugged into it and switch back and forth between guitar and theremin. Hmm... I wonder if this could be made to be installed directly into my guitar...

[amptramp]

Lots of design ideas here:

http://www.theremin.us/

Cool, thanks. I'll browse that later when I have more time.  It looks like probably only real theremins but I am making a pocket theremin that sounds more like an Atari Punk Console.

They include an optical theremin and a theremin based on CMOS gate-level IC's and these could be pocket items.

[duck_arse]

Lots of design ideas here:

http://www.theremin.us/

the 145 theremin circuit is a very good place to start hacking theremins. very good.

[PRR]

> giant pics... Tinypic? not so tiny...

Tinypic is a host; their URLs are relatively tiny.

In rare cases they will down-size a gigantic file to save their space and viewer download time. Yours look big in forum but are not what we now call gigantic.

There are many-many ways to re-size your image. Many work off-line, so you can dinker size/detail compromises quickly. Even MicroSoft has one! (I'd steer clear.) www.irfanview.com/ IrfanView does much much more, is free, has been around since the dawn of time, is safe and effective if you get it through Irfan's own site. There are also website which you upload to, they resize and return the smaller image. IMHO clumsy, but sometimes effective when you can't put any more crap on your PC.

[Ben Lyman]

> giant pics... Tinypic? not so tiny...

Tinypic is a host; their URLs are relatively tiny.

There are many-many ways to re-size your image.  www.irfanview.com/ IrfanView

Thanks PRR, that looks like a good thing to know about. I can actually do just about anything I want to my pix when I'm on my computer at home. It's when I'm on my iPhone using the tinypic app that limits what I can do. It is very fast and convenient, just select one or more pics from my library, click on "upload and copy link" all in one step, then paste to the forum. Unfortunately, I can't find any option to resize the image in either the tinypic app or my iPhone picture gallery editor.

[Ben Lyman]

The layout worked, I ended up going with only one switch to save time. I could have easily fit this in an Altoid tin with speaker, battery and all but I am running out of time to get things done so here it is, ready to go for Xmas.

[duck_arse]

I am astounded. that is exactly the sound I got outta a complete 145 build. I was going to suggest it might need a tone control, but that was before I heard it.

you could do that volume control with a second ldr, for [near] proper two handed operation. look out, clara!

[Ben Lyman]

Yes Duck, that was going to be my next question: what kind of LDR/how does it fit into the schematic for volume control?
Another change from my original plan, I wired the LDR off board and put it in a 5mm bezel. I put it all the way down inside to get some lower tones. I found by raising the LDR up closer to the top of the bezel it got more sensitive and easily hit some very high notes. Now I'm not sure which would have been better but it's good enough for my (drummer) brother to have some fun with.

[PRR]

> get some lower tones. ....some very high notes.

The pitch range will also depend a LOT on the light. Shrill in full sun. Deep in a dark dungeon.

Working with a plan similar to this, around indoor students but also an outdoor noon concert with a semi-famous composer, I learned to keep a decade's worth of caps handy to set the median pitch.

A 4-way switch with 220n 47n 10n and 2n caps may be more convenient.

You could instead tune for the dimmest light you will ever work in (usually wants a little light even on a dark stage), then use sunglass filters over the LDR for brighter light. Comes out the same. But I had more caps than sunglasses.

[duck_arse]

geeze I was hoping Paul would say volume control. ohh, well.

you'd have to try it to see a) if it works b) which way it works c) if the ldr will handle the juice.

wire an LDR and resistor in series, the output comes from the junction. LDR to out cap, resistor to ground will give more light = more volume. LDR to ground and resistor to out cap will give more volume with the dark. the resistor value? don't ask me!

[Ben Lyman]

Thanks PRR & Duck. I still have to complete one more Xmas present and my own fuzz pedal, then I can take a deeper look into this theremin thing.
Ya'll got any ideas for my pops-in-law? He already has a Boss Super Overdrive and BOSS Chorus. He's only been playing about 3 years and mostly plays open chords so I don't know if he really needs anymore pedals but my wife wants me to make him one anyway for Xmas.

[PRR]

> hoping Paul would say volume

Oh, fah. That's trivial.



The '555 output is at least 10 times bigger than any amp input really needs. "Max Level" sets some reasonable maximum output. This is set at initial test, rarely/never touched after.

I have assumed your volume hand works like muffling a phone with your hand. Hand-off is loud, covered is soft.

The photo-variable R needs another R to work against. The best value will be very different in sun or dark. "room light" knob lets you set a happy medium loudness in/on the specific room/stage you play.

Still thinking the extreme range of ambient light (5,000FC to 5FC) I have penciled a cap-selector so you can get a medium pitch in/on the specific room/stage you play.

"4.7uFd" could probably be 0.1uFd, but the cost is similar and the sketch was handy.

[duck_arse]

yes, and after I'd posted about the ldr/volume, I had a visit from Mr Ohm. he said that the speaker resistance/impedance will overload a resistive divider, and suggested the optical volume would work in front of a transistor, to buffer high R and low R. or with an amp following.

only open chords? that's me, too. build him some more fuzzes, a monster sustaining mkIII.

[Ben Lyman]

PRR- Thanks for the visual, I wanna try that out after Xmas.

only open chords? that's me, too. build him some more fuzzes, a monster sustaining mkIII.

That might be dangerous, I'm thinking of trying to stack 2 Elektras in one box with a toggle to bypass one of them. Then he could have a sort of OD/dist option in one pedal

[PRR]

> Mr Ohm. he said that the speaker resistance/impedance

He's right again.

I was *assuming* a proper Theremin studio would have a Nice Amplifier/Speaker unit. Which would drive from this divider fine.

Looking back I realize these are stocking-stuffers. I say forget the hand-wave volume control-- you can't have-it-all for 19 cents.

[Ben Lyman]

Thanks again PRR. The stocking stuffer (w/spkr) is done but I still want to (eventually) build one to use w/my guitar rig so your info is very useful.... maybe even make it small enough to fit in my guitar... hmm....