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View Source on GitHub

with MIT License

How To Install

in the Arduino IDE

Detect human presence and touch from behind several millimeters of material, or detect change in water levels from the outside of a plastic container. This library is meant to help determine change in relative capacitance for the reasons above, and not for calculating exact capacitance.

Relative capacitance is found by measuring how long it takes for an Arduino send-pin to charge a receive-pin to HIGH (in microseconds). Changes in the electrical field around a sensor connected to the receive pin (such as a human passing by, or water filling up, or a motor turning on) have a measurable impact on the amount of time it takes to charge the receive pin.

Many of these charge and discharge readings are taken, then averaged within the library to reduce variability and give a more clear answer of what the sensor is reading. This is done without delay so it only has a small impact on the main loop() performance. See the Example below for help wiring and programming the Arduino with this library.

1. Connect Arduino digital pin 2 to a 10MegΩ resistor
2. Connect the other end of the 10MegΩ resistor to Arduino digital pin 3
3. Connect Arduino digital pin 3 to a piece of conductive material (aluminum foil)
4. Cover the conductive material with non-conductive material (tape)
5. Load the Example Sketch onto the Arduino
6. Open a serial connection at 115200 baud to see the reported values
7. Touch or move your hand by the sensor

#include <RBD_Capacitance.h>

RBD::Capacitance cap_sensor(2, 3); // send, receive pins

void setup() {
  Serial.begin(115200);
}

void loop() {
  cap_sensor.update();

  if(cap_sensor.onChange()) {
    Serial.println(cap_sensor.getValue());
  }
}

Sensitivity is how far away the sensor can detect things, or how much resolution you have to recognize change in the sensor readings.

• Increase Sensitivity by either adding more resistors in series (20Meg, 30Meg, or more), or increase the surface area (size) of the piece of aluminum used as the sensor.
• Decrease Sensitivity by either lowering the amount of resitance (use only 1Meg or less), or decrease the surface area (size) of the piece of aluminum used as the sensor.

Variability is how wildly the sensor readings fluctuate. This library helps adjust the variability by taking a moving average of many readings over time. This is done without delay so it has little impact on the main loop() performance.

• Less Variable readings that don't fluctuate so quickly can be achieved by increasing the sample size: setSampleSize(1000).
• More Variable readings that fluctuate quickly can be achieved by decreasing the sample size: setSampleSize(10).

You must continuously call update() inside of loop() in order to use theReal-Time methods tagged below.

RBD::Capacitance

• constructor(send_pin, receive_pin)
• .setSampleSize(value)
• .update()
• .start()Real-Time
• .isFinished()Real-Time
• .getValue()Real-Time
• .onChange()Real-TimeEvent

RBD::Capacitance cap_sensor(2 ,3);

void setup() {
  ...
}

void setup() {
  cap_sensor.setSampleSize(1000);
}

cap_sensor

.update()

This must be call continuously from within the loop() to move the library along in real-time.

EXAMPLE SKETCH

void loop() {
  cap_sensor.update();
}

void setup() {
  cap_sensor.start();
}

void loop() {
  cap_sensor.update();
}

void setup() {
  cap_sensor.start();
}

void loop() {
  cap_sensor.update();

  if(cap_sensor.isFinished()) {
    ...
  }
}

void setup() {
  cap_sensor.start();
}

void loop() {
  cap_sensor.update();

  if(cap_sensor.isFinished()) {
    Serial.println(cap_sensor.getValue());
  }
}

void loop() {
  cap_sensor.update();

  if(cap_sensor.onChange()) {
    // code only runs once per event
    Serial.println(cap_sensor.getValue());
  }
}