Arduino as Capacitive Sensor

the file is to big to fit on the Arduino board. Why can this be??

The floating point used will presumably add quite a bit of code to a sketch...

So what can I do about that? I'm really newbie to this.. Learning as I go..

Thanx for your time and help

Strange, maybe you have a older version of the arduino. I looked at mine and I still have plenty of space left after uploading the code. Weird.
It could the float variable like westfw said but that I would find this strange. That would mean you are very very limited then. Try without the two variable I added, so at least you could see something in the Serial Monitor if that's the problem. It's the button next to the Upload one. Upload your code, when done click this button and wait a few second.

// CapSense.pde
// Paul Badger 2007

int  i;
unsigned int x, y;
float accum, fout, fval = .07;    // these are variables for a simple low-pass (smoothing) filter - fval of 1 = no filter - .001 = max filter
int ledPin = 5;   // select the pin for the LED

void setup() {
  Serial.begin(9600);

  //DDRB=B101;     // DDR is the pin direction register - governs inputs and outputs- 1's are outputs
  // Arduino pin 8 output, pin 9 input, pin 10 output for "guard pin"
  //  preceding line is equivalent to three lines below
  pinMode(8, OUTPUT);     // output pin
  pinMode(9, INPUT);      // input pin
  pinMode(10, OUTPUT);    // guard pin
  digitalWrite(10, LOW);  //could also be HIGH - don't use this pin for changing output though
  pinMode(5, OUTPUT);

  analogWrite(ledPin,255);
  delay(10);
  analogWrite(ledPin,0);
}

void loop() {
  y = 0;        // clear out variables
  x = 0;

  for (i=0; i < 4 ; i++ ){       // do it four times to build up an average - not really neccessary but takes out some jitter

      // LOW-to-HIGH transition
    //PORTB = PORTB | 1;                    // Same as line below -  shows programmer chops but doesn't really buy any more speed
    digitalWrite(8, HIGH);    
    // output pin is PortB0 (Arduino 8), sensor pin is PortB1 (Arduinio 9)                                    

    //while ((PINB & B10) != B10 ) {        // while the sense pin is not high
    while (digitalRead(9) != 1) {    // same as above port manipulation above - only 20 times slower!                
      x++;
    }
    delay(1);

    //  HIGH-to-LOW transition
    // PORTB = PORTB & 0xFE;                // Same as line below - these shows programmer chops but doesn't really buy any more speed
    digitalWrite(8, LOW);              
    //while((PINB & B10) != 0 ){            // while pin is not low  -- same as below only 20 times faster
    while(digitalRead(9) != 0 ) {     // same as above port manipulation - only 20 times slower!
      y++;  
    }

    delay(1);
  }

  fout =  (fval * (float)x) + ((1-fval) * accum);  // Easy smoothing filter "fval" determines amount of new data in fout
  accum = fout;

  Serial.print((long)x, DEC);    // raw data - Low to High
  Serial.print( "   ");
  Serial.print((long)y, DEC);    // raw data - High to Low
  Serial.print( "   ");
  Serial.println( (long)fout, DEC); // Smoothed Low to High

}

Good Luck.

I fixed the problem with size.. Was working in an old version of Arduino - so now it's no prob.
But I don't seem to get any signal, numbers or anything out..
koser.dk/mads/arduino.jpg
What could be the problem?

Thanx for your time

I think you have wired correctly. Do it like on the second picture. On yours, the pin8 and 9pin are not connected as they are on 2 seperated parts. The 2 two parts are not connected. See what I mean?

I'm not sure I understand the last part you write.. But I tryed using pin13 and the small LED blinks.. :slight_smile:
How would I print the exact signal/numbers that is recieved - I need to use these numbers..

Thanx again

//Mads

I got this error when I exported to the board::

Error inside Serial.()

gnu.io.PortInUseException: Unknown Application

at gnu.io.CommPortIdentifier.open(CommPortIdentifier.java:354)

at processing.app.Serial.(Serial.java:127)

at processing.app.Serial.(Serial.java:72)

at processing.app.Uploader.flushSerialBuffer(Uploader.java:67)

at processing.app.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:69)

at processing.app.Sketch.upload(Sketch.java:1699)

at processing.app.Sketch.exportApplet(Sketch.java:1761)

at processing.app.Editor$42.run(Editor.java:1955)

at java.awt.event.InvocationEvent.dispatch(Unknown Source)

at java.awt.EventQueue.dispatchEvent(Unknown Source)

at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.run(Unknown Source)

java.lang.NullPointerException

at processing.app.Serial.setDTR(Serial.java:480)

at processing.app.Uploader.flushSerialBuffer(Uploader.java:76)

at processing.app.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:69)

at processing.app.Sketch.upload(Sketch.java:1699)

at processing.app.Sketch.exportApplet(Sketch.java:1761)

at processing.app.Editor$42.run(Editor.java:1955)

at java.awt.event.InvocationEvent.dispatch(Unknown Source)

at java.awt.EventQueue.dispatchEvent(Unknown Source)

at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)

at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.pumpEvents(Unknown Source)

at java.awt.EventDispatchThread.run(Unknown Source)

What can this mean?

It could mean a few things. Is anything else running that might be using the serial port? Have any over-aggressive firewalls? Did you select the right serial port from the Tools > Serial Port menu?

I have a question about adding more capacitive touch sensors through a multiplexer. I'd like to add a bunch more sensors providing continuous data (i.e. not digital on-off buttons). The tests I've made make me concerned that I won't be able to get smooth, consistent data when reading this through a multiplexer (MC14067). I understand that with wires dangling and a breadboard one can pick up stray capacitance so it's not the best test but my tests have led me to be concerned anyway and I thought I'd ask if anyone can confirm the possibility (or impossibility) of this technique before I go through all the effort of getting a PCB made.

Here's the situation:

  1. Connecting a sensor and the resistor directly to the Arduino pins produces smooth, continuous data as my finger moves across the sensor (as long as there's some insulation over the copper - scotch tape has worked fine for my prototypes).

  2. Connecting the sensor and resistor into a breadboard and then on to the Arduino also produces smooth, continuous values (though slightly different than number 1).

  3. Connecting the pins through a multiplexer to read multiple sensors produces approximately accurate results but the values jump around a bit. That is, it won't be completely random but with a constant finger position it will jump back and forth within a small range. Too much change to use smoothing in the code I think.

The fact that both 1 and 2 work well leads me to believe that it's the multiplexer, not the breadboard/dangling wires that is causing the problem.

Anyone have any thought on how/if this setup could work?

Thanks.

P.S. Thanks for sharing this cool technique!

P.P.S - Well, I just figured something out. If I reverse the order of the HIGH-to-LOW and LOW-to-HIGH transition sections, I get much smoother results. Still not quite as smooth as without the multiplexer, but I'm more optimistic about getting this to work.

Any further thoughts would still be appreciated.

Thanks.

Hi,
A guy named Terry Fritz did some work on using multiple capacitance sensors together. It's not exactly an answer to the multiplexer question, but it could be helpful. I'm not techy enough to know exactly how, but he found a way to clean up and amplify noisy signals from the antennas.
Check it out: http://thereminvision.com/version-2/TV-II-index.html

:slight_smile: :slight_smile: :slight_smile: :slight_smile:

I've potentially saved a HELL of a lot of money coming across this forum! I'm wanting to toggle a switch like you would with one of those tactile lamps that you touch a few times to get different degrees of intensity. What I'd really, REALLY appreciate would be if someone pointed me in the right direction for achieving this using Max/MSP as the programming language (I'm using 'simplemessagesystem' to interface the Arduino with Max). Would it be too much of a challenge?

Thanks for your time,

Gennaro

:slight_smile: :slight_smile: :slight_smile: :slight_smile:

Hi all,

I'm a rookie to this Arduino game but I got this code working and it suits my project really well. However, I don't need to read various degrees of pressure, I merely need an on/off register. I know I need to add a boolean but I have no idea where... Any ideas?

Any help is a plus :slight_smile:

I am really interested in to get touch sensiting working together with max/msp, has anyone did that?
I am using the arduino2Max patch to get Arduino talk to max/msp.

hey,

i'm trying to do the same. i was initally using the capsense code but abandoned it because i couldn't seem to create multiply capacitive sensors from it. i'm not that hardcore a programmer you see.

instead, i found this code Arduino Playground - CapacitiveSensor

which works perfectly in arduino, the numbers are outputting and i'm trying to use with the arduino2max patch but no joy. as the pins are declared in the arduino code, surely the max patch should read the digital pins? any help is really appreciated.

Cheers

I'm currently building a capactive measurement system as part of my PHd, I've found, depending on what accuracy you want, that the best way is to use a sigma delta modulation technique. You can find this in Analog Devices AD774x series of Capacitive to Digital Converters. These chips go from one channel to 12 channels for mounting capacitive electrodes and have resolutions between 8 and 24 bits over full scale ranges of around 25pF with a bit of calibration, obviously, that gives a lot of sensitivity.

The chips communicate with a host through the i2c bus, so you ca use Arduino's wire library to get the data out of the slave chip (I sweated over a prototype function for a PIC i2c protocol for months when I found arduino!) and use that to manipulate the data anyway you want.

the only thing is that these chips are only available in TSSOP form so can be a bit of a pain in the arse to solder, however it's quite a nice solution as I am finding out.

What is the purpose of the guard pin (pin 10)? The code seems to work just as well without it...

You are correct that the guard pin doesn't do much and can easily be omitted. This was a klugy way to implement a technique which is used with op amps and other high impedance (low current) circuits.

You can now use the [[Arduino Playground - HomePage capSense library]] and use any pins you want. The results will vary a bit from pin to pin though.

But if you do want to make the wire insensitive and only the foil at the end sensitive, use shielded audio wire and ground the shield on the duino end only. (Make sure the shield on the other end doesn't touch the sensor, or it won't work.

Paul

What is the difference between this and Arduino Playground - CapacitiveSensor? Is the one wire method only for direct touch, while this can sense a longer distance?