therminish

[coreybox]

Can anyone help show me a way to do the zvex thing with his probes. how can i replace a knob with a thermin?

thanks

corey

[Johnny G]

this requires a bit of tricky electronics and probablly alot of tweaking but its doable

basically the way it works is you have an oscillator. you then connect a large metal plate to the oscillator (connection place differes depending on what oscillator you're using) as you move whichever pat of your body closer to the plate it creates a variable capacitance between you and the plate with your body efectivly being ground. this change in capacitance is enough to affect the oscillator frequency and so you have a variable oscillator. the signal from this is then fed through a filter that will change the amplitude of the signal depending on the frequency (a simple LC filter to ground can do this)

once youve got that you just have a circuit to turn the changing AC signal into a changing DC voltage. then you can use it to control a Jfet and heypresto.

the electronics of it are a bit more complex than that. have a look around on the net for info on theremins, you'll find loads of stuff and a few sites that will explain it much better than i do.

as for the Zvex probes i have no idea what sort of oscillators he uses, NAND gates or some proper discrete transistor hartley/colpitts style thing. id love to know *yeah it is an unsubtle hint if you feel like sharing anything Mr Vex*

best advice is to just go out and dig up whatever you can on theremins. study a few schematics and learn all you can about building high frequency oscillators (the ones in theremins normally work at about 100 to 200 KHz), thats the tricky part imho

[Johnny G]

should have addedthis

heres a good site that has some of the basics of oscillators

http://my.integritynet.com.au/purdic/oscillators.htm

[The Tone God]

I did something many years ago that was like a simple theremin. I forget all the details, there in some notebook somewhere, but what I can remember is I used a logic gate oscillator setup in the RF range. I then hooked up an attenna to the junction of the timing cap so when my  hand passed by it would vary the frequency via the capacitence change. I used the signal to control the brightness of an LED, sort of like a PWM, inside a optocoupler which then was connected to whatever I wanted. Fun stuff.

I don't know how Mr. Vex goes about it. This is just how I did it.

Andrew

[mlabbee]

This might be a simple place to start - it's on my list of things to try, but still a way off:

http://www.seanet.com/~tpaddock/c2cv.html

[bobbletrox]

I think the Fuzz probe uses an optocoupler type affair.  I have a picture of the insides of a Fuzz Probe where you can see the little board that has an IC and two trimmers on it, and the optocoupler is located on the main board.

I was tryin' to figure out how to add a proximity plate to control the width of a PWM effect a while back but never figured it out.  It would have been an economical build because both circuits could share the same Schmitt Trigger (that was assuming it could be done with a schmitt).

[coreybox]

short term i basicallly want to build vex's volume probe, since it is (1) discontinued permently and (2) im poor. long term i want to try and build this into some other effects. im still totally clueless as how to even begin. the above links are just bits and pieces that i (due to my crappy knowledge in this field) can not begin to put together. im hopeing to get a fuzzprobe for christmas...so maybe i can beging to understand by looking inside of it.......but it would be nice to learn now! ha well anyways i hope yall can help me.

thanks!

corey

[coreybox]

also could yall expand on the optocoupler method. first i dont know what optocoupler to get, or how to use one. samething with the logic gate oscillator. the tone god seems to knwo what he is talking about, but i dont know how to apply anything he said

[The Tone God]

I think this will be the first post I have answered that contains the word "yall". Its so cute.

Just to answer your questions in brief. An optocoupler in a more general sense is a device that allows you to couple signals optically. Thus keeping the signals isolated from each for noise and other operational reasons.

Optocouplers come in many varities but for our use we want one that allows the change of a resistive element through power. This typically means the use of an Light Dependant Resistor (LDR) with a LED. An LDR changes resistance based on the amount of light it comes in contact with. By controling the power going through the LED, which in turn controls the brightness shined on the LDR we can control the resistive value of the LDR. From there the LDR can be used to control whatever effect parameter we want.

As to where to get one you can get them a various electonic stores or you can make one yourself by taking an LDR and an LED, sticking them in some heat shrink tubing, and sealing them together. Taa daa.

As for the oscilator its pretty simple. Its just involved a logic gate, like a inverter gate, a capacitor, and usually a resistor or two. As to how to interface it with the human portion do some reasearch on Theremins. Heres a good site with some schematics including some simple logic gate oscilator based versions.

http://www.maxiespages.com/Articles/Theremin_tech/Circuit_diagrams_Toy_or_gadget_theremins

To find out more about how the human/capacitance relationship interacts in this regard do a search for something called "Kirchoff's Law".

Thats should get you started.

Andrew

[coreybox]

http://www.qprox.com/downloads/datasheets/qt301_106.pdf

i found that would schem. 1-1 be suitable? if so what value for Cx do you think would be ideal? also would i be able to just connect the led directly from pin 6? and last question......for the sensor part do i just get say a thin sheet of copper and solder that line to it? or is it more complex than that? thanks again

corey

[coreybox]

and ha, yes i am from Texas so "yall" is most likely forever burned into my vocabulary

[bobbletrox]

http://www.qprox.com/downloads/datasheets/qt301_106.pdf

i found that would schem. 1-1 be suitable? if so what value for Cx do you think would be ideal? also would i be able to just connect the led directly from pin 6? and last question......for the sensor part do i just get say a thin sheet of copper and solder that line to it? or is it more complex than that? thanks again

corey

I'm pretty sure you need an EPROM burning dealie for that chip.

I understand that U1A, B, and C form a variable oscillator in this circuit:
http://www.maxiespages.com/images/Theremin/minimum.gif
But it beats me how you'd get it to drive an LED or whatever.

[Paul Perry (Frostwave)]

Want a proximity detector? Then get a proximity detector from this range:
http://sharp-world.com/products/device/lineup/opto/sensor/

In particular, the linear voltage output GP2D12 (about $8).
After trying a theremin, you will be SO glad to go to infrared :wink:

Incidentally, this is the magic that flushes urinals when you step away..
Want to know "too much"? google for "ir proximity detectors" and you will find a million amateur robotics sites. The robotics guys have plenty of stuff we can steal, plus endless "how to etch PCB" storieszzzzzzzzzzz...

[coreybox]

http://sharp-world.com/products/device/lineup/data/pdf/datasheet/gp2d12_e.pdf


GP2D12?

would that be suitable. it says "analog voltage" for the output, so could i hook up a led directly to that? and then do the LDR thing?

[The Tone God]

I have a bunch of these but I belive most of mine are digital though. I belive you would want the analog version but you should take a closer look at the spec sheet. I see a couple of things you may have to deal with. Heres a hint to start you off. Look at the distance graphs.

Andrew

[coreybox]

ya ya, i did notice the distance....i just dont know what the 'best' solution for this is, and then how to take the first step. what i really need is a schematic for a theremin, or IR or something that shows me exactly how to drive the led. no thinking involved

[The Tone God]

Bingo.

Don't stop at the first sign of trouble. Maybe sink the sensor in to the case to the get the clearence. Maybe light pipes. There a few way to go about it.

There are other things with this device. You would have to deal with the supply voltage. This is a 5v device much like most logic stuff. I would also not drive a LED directly with this. You should put some kind of buffer/amplifier in between which could be a transistor or opamp stage of some kind.

I don't think there is a "best" solution. I think the optical is a good way to go so I won't knock it. There are just a number of small problems to solve. The RF theremin has problems too but thats another good way to do things as well.

You should do some more research on theremins and so forth. You are asking for something that is not commonly done around these parts. When you do that you going to have to do some thinking and learning.

Andrew

[coreybox]

http://www.qprox.com/downloads/datasheets/qt301_106.pdf


checck out figure 2-7.........so if i used this chip, then an rc circuit(im not familiar with that) then i can drive a led with this correct? on the analog out though, im not sure how to do that rc circuit,(the ic looking part on the schematic).

thanks

corey

[Paul Perry (Frostwave)]

Corey, looking at that circuit, I guess you could run a LED via a 330 ohm resistor, but you wouldn't be using the full range of the sensor.
The RC thing is just a crude smoother. The output buffer could be replaced by an op amp amplifing stage (or a transistor stage), like the part of an envelope follower or compressor where the audio signal after beign rectified is used to control a led in the classic led/ldr setup.

[coreybox]

http://www.qprox.com/downloads/datasheets/qt301_106.pdf

im looking at figure 1-1 .........have the output go into an oamp (woudl a lm 386 work? and then drive a led off that?