Human body as controller/modifier?

[aerogramma]

Hello I've been looking into integrating the human body as a controller modifier for out live sets... the audience's human bodies that is

i've started looking into the cracklebox concept and i'm not sure if i read the schematics correctly but it seems that the touchpads are just a way to add skins as a resistor thus changing the sound.

but anyway i'm not too fond of the cracklebox sound i rather go for something more like a sinewave, a deeper sound.

so i'm looking into suggestions on how to interface, say a VCO, with a human body... one thought was that you could use bodies as resitor/frequency dividers of some sort, put them in series to gradually change the frequency.

but i'm not sure how to do that, shall i go down the circuit bending rout and just bring out touchpoints from the vco circuit or...any advice?

thanks!

aero

[Inventor]

Hi aero, there are many ways to interface electronics to the human body. Biofeedback devices work by sensing skin resistance. You can use a multimeter set on resistance measurement and touch the probes to your fingers to see an example of this. A classic biofeedback device measures this skin resistance and varies an oscillator's freqency, going lower in freqency for higher resistances. That way as a person relaxes, their skin dries from lack of sweat, and the tone gets more relaxing. I'm sure you can google up some biofeedback schematics for doing this.

You can also detect the body's pulse by shining a red led into the tip of your finger and detecting the ac component of the light with a sensor, though I don't know what kind of sensor. Perhaps a phototransistor or cadmium sulfide cell.

The body also makes noises which you can detect with a microphone.

You can even detect a person's temperature from a distance by focusing light with a lens. Companies make gun-shaped temperature meters for pointing at industrial equipment and sensing temperature this way. With mirror scanners and one of those devices, I suppose you could scan the audience in a raster pattern to map their temperatures. That would be a "cool" thing to do.

In addition to direct sensing of the body, there are many sensing devices available that detect pressure, bending, motion, and the like. Also you can just give each audience member a WiiMote and detect them with Bluetooth and oscullator or some other software.

In addition, I have created a USB accelerometer device that looks like a joystick to the computer. I use the music programming language ChucK to create guitar effects and a simple drum machine by sensing the motion of the sensor.

So there are lots of options for you to consider. I'd suggest starting simple and doing something really easy like sensing skin resistance and driving a vco with it, then moving on to other approaches. Good luck and have fun!

[aerogramma]

Thanks a lot for the suggstions.. i'm quite familiar with sensors and software implementations of controlling devices

i'm thinking here something much more primitive, going straight to an oscillator, no sensor or software involved

[Inventor]

you could use a relaxation oscillator with about one MOhm in the voltage divider top side and put the skin contact as the lower resistor, send the triangle wave output into an LM386 speaker driver and there ya go. Might work or something like it.

[aerogramma]

[Inventor]

Well, I think you're on the right track. Regardless of knowing what a relaxation oscillator is, you can look at any oscillator schematic and figure out which resistor or resistors control the frequency. Then it's a matter of putting those in the megOhm range by setting the cap value and using a pair of skin electrodes in place of the resistor...

[aerogramma]

[Inventor]

Well, the frequency of any ressitor-capacitor based oscillator is typically set by an RC time constant. If you remember "units" from school, Ohms * Farads = seconds. Weird but true. So you want your Ohms times your Farads to come out to be around 1 ms. That would give you 1 kHz audio frequency. Of course it's much more complpex than that and circuit-dependent but that's the rough general idea.

So you look at the circuit and it has C1 value of capacitance and R1 value of resistance. Say R1 is 100 kOhms. You want R1 to be about 1 MOhm. So you decrease the capacitor by a factor of 10.

Note that although I said you should completely remove the resistor and replace it with a skin sensor, another option would be to use a 1 MOhm resistor and just put the skin sensor in parallel with it. That would not be as sensitive but might work better overall.

If you have any more questions just ask away. Cheers.

[aerogramma]

thank you very much sir,

will experiment upon your suggestions in the next few days