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--- en:iot-open:hardware2:sensors_optical [2023/08/25 12:10] – ekontoturbo
+++ en:iot-open:hardware2:sensors_optical [2023/11/23 12:38] (current) – pczekalski
@@ Line 1: / Line 1: @@
+====== Optical Sensors ======
+{{:en:iot-open:czapka_b.png?50| General audience classification icon }}{{:en:iot-open:czapka_e.png?50| General audience classification icon }}\\
+== Optocoupler ==
+An optocoupler is a device that combines light-emitting and receiving devices in one package. Mainly, it combines the infrared light-emitting diode (LED) and a phototransistor.\\
+There are three main types of optocouplers:
+  * an **optocoupler of a closed pair configuration** is enclosed in the dark resin and is used to transfer signals using light. This type of optocoupler is not a sensor itself but is used for ensuring electrical isolation between two circuits;
+  * a **slotted optocoupler** has an open space between the light source and the sensor; external objects can obstruct light and thus can influence the sensor signal. It can be used to detect the presence of flat objects, measure rotation speed, vibrations or serve as a bounce-free switch;
+  * a **reflective pair configuration**, the light signal is perceived as a reflection from the object's surface. This configuration is used for proximity detection, surface colour detection and tachometer.
+A symbol, sample optocoupler and its connection to the microcontroller are present in figures {{ref>optocoupler1}}, {{ref>optocoupler2}} and {{ref>optocoupler3}}.
+<figure optocoupler1>
+{{ :en:iot-open:getting_familiar_with_your_hardware_rtu_itmo_sut:arduino_and_arduino_101_intel_curie:optocoupler.jpg?100 | Optocoupler symbol}}
+<caption>An optocoupler symbol</caption>
+</figure>
+<figure optocoupler2>
+{{ :en:iot-open:getting_familiar_with_your_hardware_rtu_itmo_sut:arduino_and_arduino_101_intel_curie:elitr9909_c.jpg?100 | ELITR9909 reflective optocoupler sensor}}
+<caption>ELITR9909 reflective optocoupler sensor</caption>
+</figure>
+<figure optocoupler3>
+{{ :en:iot-open:getting_familiar_with_your_hardware_rtu_itmo_sut:arduino_and_arduino_101_intel_curie:sch_apz_shemas_optocoupler.png?200 | Arduino Uno and optocoupler schematics}}
+<caption>Arduino Uno and optocoupler schematics</caption>
+</figure>
+An example code:
+<code c>
+int optoPin = A0;   //Initialize an analogue A0 pin for optocoupler
+int optoReading;    //The analogue value reading from the optocoupler
+int objecttreshold = 1000; //Object threshold definition
+int whitetreshold = 150;   //White colour threshold definition
+void setup ()
+{
+  //Begin serial communication
+  Serial.begin(9600);
+  //Initialise the analogue pin of the optocoupler as an input
+  pinMode(optoPin, INPUT);
+}
+void loop ()
+{
+  optoReading = analogRead(optoPin); //Read the value of the optocoupler
+  Serial.print ("The reading of the optocoupler sensor is: ");
+  Serial.println(optoReading);
+  //When the reading value is lower than the object threshold
+  if (optoReading < objecttreshold) {
+    Serial.println ("There is an object in front of the sensor!");
+    //When the reading value is lower than the white threshold
+    if (optoReading < white threshold) {
+      Serial.println ("Object is in white colour!");
+    } else { //When the reading value is higher than the white threshold
+      Serial.println ("Object is in dark colour!");
+    }
+  }
+  else { //When the reading value is higher than the object threshold
+    Serial.println ("There is no object in front of the sensor!");
+  }
+  delay(500); //Short delay
+}
+</code>
+== Colour Sensor ==
+This type of sensor gives information about the colour of the light illuminating the sensor surface. Because computers often use RGB (red, green, blue) colour schemes, the sensor returns three values representing the intensity of three components. Colour sensors usually contain white LEDs to illuminate the surface, which colour should be distinguished by them. The colour sensor uses an SPI or TWI interface to send readings. Some models of colour sensors include an additional gesture detector which recognises simple gestures (up, down, left, right).\\
+The sample device is present in figure {{ref>tcs1}} and the connection circuit in figure {{ref>tcs2}}.
+<figure tcs1>
+{{ :en:iot-open:hardware2:20230925_114221_-_kopia.jpg?200 | TCS34725 RGB colour sensor module}}
+<caption>TCS34725 RGB colour sensor module</caption>
+</figure>
+<figure tcs2>
+{{ :en:iot-open:hardware2:tcs34725_schematic.png?200 | Connection of the TCS34725 and microcontroller}}
+<caption>Connection of the TCS34725 and microcontroller</caption>
+</figure>
+<code c>
+#include <Wire.h>
+#include "Adafruit_TCS34725.h"
+// Example code for the TCS34725 library by Adafruit
+// Sensor class
+Adafruit_TCS34725 rgb_sensor = Adafruit_TCS34725();
+void setup(void) {
+  Serial.begin(9600);
+  Wire.begin(5,4);           //SCL SDA
+  pinMode(21, OUTPUT);       //Pin 21 controls LED
+  digitalWrite(21,LOW);      //Turn off onboard LED
+  if (rgb_sensor.begin()) {  //Initialise RGB sensor
+    Serial.println("RGB sensor present");
+  } else {
+    Serial.println("No TCS34725 found");
+    while (1);
+  }
+}
+void loop(void) {
+  uint16_t r, g, b, unfiltered, lux;
+  rgb_sensor.getRawData(&r, &g, &b, &unfiltered);
+                             //read RGB and unfiltered light intensity
+  lux = rgb_sensor.calculateLux(r, g, b);
+                             //calculate illuminance in Lux
+  Serial.print("Lux: ");     //print calculated Lux value
+  Serial.print(lux, DEC);
+  Serial.print(" - ");
+  Serial.print("R: ");       //print red component value
+  Serial.print(r, DEC);
+  Serial.print(" ");
+  Serial.print("G: ");       //print green component value
+  Serial.print(g, DEC);
+  Serial.print(" ");
+  Serial.print("B: ");       //print blue component value
+  Serial.print(b, DEC);
+  Serial.print(" ");
+  Serial.print("C: ");       //print unfiltered sensor value
+  Serial.print(unfiltered, DEC);
+  Serial.println(" ");
+  delay(1000);
+}
+</code>