Capacitive Proximity Sensor

Using Arduino Project Guidance
1

Hi. How can I change this code so that it will only detect plastic? Is it possible? Thankyou.

This is the sketch:

float metalDetected;
int monitoring;
int metalDetection = 1;
int countRaw = 0;

void setup(){
Serial.begin(9600);
}

void loop(){
monitoring = analogRead(metalDetection);
metalDetected = (float) monitoring*100/1024.0;
Serial.print(“Initializing Proximity Sensor”);
delay(500);
Serial.print(“Please wait…”);
delay(1000);
Serial.print(“Metal is Proximited = “);
Serial.print(metalDetected);
Serial.println(“%”);
if (monitoring > 250)
countRaw ++;
Serial.println(“Metal is Detected”);
Serial.print(“Number of Detection > “);
Serial.println(countRaw);
delay(1000);
}
2

Don’t cross post!

http://forum.arduino.cc/index.php?topic=579140.0

3

Code is secondary only.

Capacitive senors react to conductive material strong, non-conductive less strong, but you can't use them to distinguish one material from the other.

Now if you would tell us what you're actually trying to do, we may be able to come up with possible solutions.

4

wvmarle:
Code is secondary only.

Capacitive senors react to conductive material strong, non-conductive less strong, but you can't use them to distinguish one material from the other.

Now if you would tell us what you're actually trying to do, we may be able to come up with possible solutions.

we're going to make a reverse vending machine concept thesis wherein only the plastic bottles are accepted and reject other kinds of bottles in exchange of points. now, we bought a capacitive sensor because it sense plastic bottles, our problem now is it also detect other materials like metal, we dont know what are we going to replace to the code above so that it will only detect plastic and reject other materials.

5

That's a tall order.
I'm thinking of a break beam sensor to detect the presence of a bottle.
I really don't know how commercial machines do this. Probably a combination of sensors.
Shape is another major one: two holes, one that's too small for your bottle (sorts out smaller bottles), one that's just big enough for your bottle (sorts out bigger ones).
Bottles come in limited size and shape, make use of that.
Two or three break beam sensors at strategic heights will tell you whether your bottle is of the correct height as well.
Weight can give you the material - and tell whether the bottle is empty. Plastic bottles should be very light in weight, but do allow for residue and dirt in your weight allowance.

6

Capacitive sensors principally detect nearby conductors, like metal or fingers. The object being
detected forms a capacitor plate.

To discriminate materials based on their dielectric constant requires accurate geometry in the sense
cell, for instance pieces of a given thickness - this is not practical for your machine.

You could combine a metal detector and a break-beam sensor - if the break beam triggers and the metal
detector doesn't, its something not metal...

7