Q4L3 _ AnalogRead Function

Lesson 14: Analog Read

• Prepared by: Jovie Bon B. Cabarles

The analogRead Function

• Purpose: Allows Arduino to read analog signals using pins A0 - A5.

• Sensors: Some sensors output an analog signal that can be read by Arduino.

• Syntax: analogRead(pin);

  • pin: Specifies the Arduino pin number to read/input from.

Signal Resolution

• A0 to A5 pins have 10-bit resolution.

  • Values: 0 to 1023 corresponding to 0V to 5V.

  • Conversion:

    • Formula: Voltage = (5/1023)*signal

    • Example: If the signal read is 523,

      • Voltage = (5/1023) * 523 = 2.5562V.

Basic Syntax for Analog Read

• Arduino Code Structure for Reading:

  • void setup() { pinMode(pin, INPUT); }

  • void loop() { analogRead(pin); }

  • Where pin specifies the Arduino pin number.

Example Application: Photoresistor

• Photoresistor: A type of resistor whose resistance varies with light intensity.

• Schematic: Display simulation on Tinkercad when clicking the photoresistor.

  • Brightness simulation represented by a slider.

Voltage Divider Circuit

• Use of a voltage divider using a photoresistor and resistors.

• Formula for Voltage Drop:

  • V2 = Vs * (R2 / (R1 + R2))

  • Example Calculations:

    • For R2 = 1k, V2 = 0.88V

    • For R2 = 2.5k, V2 = 1.77V

• Impact of Resistance Changes: Voltage drop across resistors varies with resistance.

Wiring Diagram and Connections

• Diagrams depict connection of a photoresistor to A0.

• Behavior: If light sensed is dim, resistance is high, yielding a higher voltage drop, and vice versa.

Arduino Coding for Reading Signals

• Declare pin A0 as INPUT to read signal:

  • int Photoresist1;

  • void setup() { pinMode(A0, INPUT); Serial.begin(9600); }

  • void loop() { Photoresist1=analogRead(A0); Serial.println(Photoresist1); }

Serial Monitor Usage

• Opens to observe data read by the photoresistor.

• Essential function: Serial.begin(9600); in setup.

• To display readings: Serial.println(Photoresist1);

Signal Reading and Simulation

• Start simulation and observe numerical outputs representing signals read by A0.

• Adjusting the photoresistor output will show corresponding signal changes in the serial monitor.

Problem #2: LED Control Based on Light Intensity

• New Circuit Addition: Incorporate an LED.

  • Arduino should turn on LED if the signal from A0 is greater than 500:

    • if (Photoresist1 > 500) { digitalWrite(LED, HIGH); }

• Else Condition: Turn off the LED when below threshold:

  • else { digitalWrite(LED, LOW); }

Example: Automated Light Switch Simulation

• When photoresistor detects an analog signal over 500, it activates the LED as a light switch reactant.

Activities for Practice**

• Use two photoresistors to control an LED based on relative brightness.

• Conditional logic required if Photoresistor1 senses more light than Photoresistor2 to switch the LED on, otherwise keep it off.

• Further challenge: Blink LED thrice for 5 ms if Photoresistor1 is dimmer than Photoresistor2.

Conclusion

• Demonstrating practical applications of analogRead function in Arduino and understanding component interactions through code and circuit behaviors.