13. Ambient Light Sensor

This lesson uses: Arduino UNO R3 board, TinkerBlock TK20 Ambient Light module, jumper wires (or breadboard). Learn to read light with analog input; outcome: serial shows light value (0–1023)—cover light and value drops, shine light and value rises.

1. Wiring

Connect TK20 Ambient Light to Arduino:

• GND → Arduino GND
• VCC → Arduino 5V
• SIGNAL → Arduino A0
• NC leave unconnected

2. New sketch

1. Arduino IDE: File → New (or Ctrl/Cmd + N) to create a blank sketch
2. Confirm board and port are selected (same as Lesson 01)
3. Type the code below into the default setup() and loop() yourself

3. Program structure

Same as last lesson: two fixed blocks setup() and loop().

• setup(): Start the serial port (to see values on the computer); runs once.
• loop(): Keep repeating “read A0 → store in variable → print to serial → short delay”.

After the code runs, cover the sensor or shine a light and the serial light value will change.

4. Code to write

Type the code below line by line into setup() and loop() (do not copy-paste; typing it yourself helps you remember):

#define LIGHT_PIN A0   // Light sensor on A0

void setup() {
  Serial.begin(9600);   // Start serial, baud 9600
  Serial.println("Ambient light sensor program started");
}

void loop() {
  int val = analogRead(LIGHT_PIN);   // Read A0, store in val (0-1023)
  
  Serial.print("Light: ");
  Serial.println(val);   // Print val (higher = brighter)
  
  delay(200);   // 200 ms
}

Program notes

Overall idea: A0 reads the TK20's phototransistor, whose current rises with light; a 4.7 kΩ resistor on the block turns that current into a voltage; ADC 0–1023, higher means brighter. Print to serial for observation.

5. Hands-on

1. After entering the code, click Verify (✓) to compile
2. Click Upload (→) to upload to the board
3. Open Serial Monitor (Tools → Serial Monitor, baud 9600)
4. Watch the Serial Monitor:
   • Cover the TK20 module: light value decreases
   • Shine a phone flashlight on it: light value increases
   • In a lit room: usually well under half the scale, roughly 50–250; a phone flashlight close up reads near the top
5. Try different lighting and observe the values

Expected result:

Serial monitor shows:

Ambient light sensor program started
Light: 142
Light: 139
Light: 3
Light: 941
Light: 140
...

Note: TK27 Analog MIC Sensor is analog too, but it reads differently: its output rests at a level and swings around it when a loud sound arrives, so a single reading says little. Its handbook shows how to read the swing.

Proceed to Lesson 14.

6. Common issues

Edit this page — content/guides/tinkerblock-workshop/13-ambient-light-sensor.mdx