INTRO - ElectricBody+Capacitance

ARDUINO AND CAPACITIVE SENSING

Capacitive Sensing can sense the electrical capacitance of the human body.

All the sensor setup requires is a medium to high value resistor and a piece of wire and a small (to large) piece of aluminum foil

on the end. At its most sensitive, the sensor will start to sense a hand or body inches away from the sensor.

In order to do capacitive sensing we must download this library. http://playground.arduino.cc/Main/CapacitiveSensor?from=Main.CapSense

The code we are using is based on a intro sketch from this Library by Paul Badger. We will map the variables from the sensor input of a capacitive sensor to

the sound generated by arduino's chip and output this to an 8 ohm speaker. Our sensor input can use foil or barepaint as a sensor.

Details on how to make a sensor with barepaint: http://www.bareconductive.com/make/building-a-capacitive-proximity-sensor-using-electric-paint/

We use a speaker with arduino's built in tone library.

//CODE

//add the capsense library to arduino

#include <CapacitiveSensor.h>

//COMBINES :

/*

* CapitiveSense Library Demo Sketch

http://playground.arduino.cc/Main/CapacitiveSensor?from=Main.CapSense

* Paul Badger 2008

* Uses a high value resistor e.g. 1M- 10M between send pin and receive pin

* Resistor effects sensitivity, experiment with values, 50K - 50M. Larger resistor values yield larger sensor values.

* Receive pin is the sensor pin - try different amounts of foil/metal on this pin

*/

//and

/* Pitch follower -Plays a pitch that changes based on a changing analog input

created 21 Jan 2010 modified 31 May 2012 by Tom Igoe, with suggestion from Michael Flynn

This example code is in the public domain.

http://www.arduino.cc/en/Tutorial/Tone2

this uses basic inbuilt tone library distributed with arduino

for additional sound control install full contributed library

*/

//create an instance of capacitive sensor

// Capsensor between pins 4 & 2, pin 2 is sensor pin, add a wire and or foil if desired

CapacitiveSensor cs_4_2 = CapacitiveSensor(4,2);

void setup()

{

cs_4_2.set_CS_AutocaL_Millis(0xFFFFFFFF); // turn off autocalibrate on channel 1 - just as an example

Serial.begin(9600);

//Begin Serial monitor and set serial to rate of 9600 bauds

}

void loop()

{

//timer

long start = millis();

//setting for capacitive sensor input

long input1 = cs_4_2.capacitiveSensor(30);

//print output to serial window

Serial.println(input1);

//we are using arduinos built in tone library with pitch

//we are using the map function to change sound map input range

//starting at 100 and up to 3000 to between 120 and 1500 hz

int thisPitch = map(input1, 100, 3000, 120, 1500);

//we are only outputting to speaker if the value is greater than 50hz

if (thisPitch>50){

// play the pitch to digital pin 9

//syntax and variables for tone(pin, frequency, duration)

tone(9, thisPitch, 10);

// arbitrary delay to limit data to serial port

delay(50); // delay in between reads for stability

}

}

For more info on how to play notes etc see ITP's intro to tone (you need to add a tab to arduino for the file pitches.h)

http://itp.nyu.edu/physcomp/labs/labs-arduino-digital-and-analog/tone-output-using-an-arduino/

GROUNDING ISSUES WITH CAPACITIVE SENSING

The grounding of the Arduino board is very important in capacitive sensing. The board needs to have some connection to ground, even if this is not a low-impedance path such as a wire attached to a water pipe.

Capacitive sensing has some quirks with laptops unconnected to mains power. The laptop itself tends to become sensitive and bringing a hand near the laptop will change the returned values.

Connecting the charging cord to the laptop will usually be enough to get things working correctly. Connecting the Arduino ground to an earth ground (for example, a water pipe) could be another solution.

Another solution that seems to have worked well on at least one installation, is to run a foil ground plane under the sensor foil (insulated by plastic, paper, etc.), and connected by a wire to ground. This worked really well to stabilize sensor values and also seemed to dramatically increase sensor sensitivity.

from : http://playground.arduino.cc/Main/CapacitiveSensor?from=Main.CapSense

Makey Makey uses capacitance to enable it to work.

MORE INFO ON MAKEY MAKEY HERE