Activity 3: Environmental Sensors

Overview

In this activity, you will wire and experiment with three types of environmental sensors: a temperature sensor (TMP36), a light sensor (photoresistor module), and a soil moisture sensor. You’ll test how each sensor responds to different environmental conditions and document your findings. This is a team activity where you’ll build a multi-sensor environmental monitoring system.

Teams: Work in groups of 2-3 students

Due Date: Thursday, February 6th by 11:50 AM

Learning Objectives

By completing this activity, you will:

  • Wire and operate temperature, light, and moisture sensors
  • Read and interpret analog sensor values
  • Calibrate sensors for different conditions
  • Document experimental findings and observations

Requirements

What You Must Demonstrate

  1. Correct wiring of all three sensors to the Arduino Uno
  2. Serial Monitor output showing all three sensor readings
  3. At least 2 experiments per sensor testing different conditions
  4. Documentation of your experiments and findings in experiments.md
  5. Push to GitHub and demonstrate to instructor

Materials Needed

  • Arduino Uno
  • USB cable
  • Breadboard
  • Jumper wires
  • TMP36 temperature sensor (3 pins)
  • Photoresistor module (4 pins)
  • Soil moisture sensor (3 pins)

GitHub Classroom

Accept the assignment at: https://classroom.github.com/a/hZZHXESz

Sensor Details

TMP36 Temperature Sensor

Principle: Voltage output proportional to temperature

Specifications:

  • Range: -40°C to +125°C
  • Output: 10 mV per °C, 500 mV offset at 0°C
  • Formula: temp_C = (voltage - 0.5) × 100

Wiring (3 pins):

  • Left pin (red): 5V
  • Middle pin (yellow): A0 (analog output)
  • Right pin (black): GND

Photoresistor Module

Principle: Resistance changes with light intensity

Specifications:

  • 4-pin module with built-in comparator
  • Use AO (analog out) pin for readings
  • Values 0-1023 (higher = more light)

Wiring:

  • VCC: 5V
  • GND: GND
  • AO: A1 (analog output)
  • DO: Not used for this activity

Soil Moisture Sensor

Principle: Measures soil conductivity (wetness)

Specifications:

  • 3-pin sensor
  • Analog output (0-1023)
  • Higher value = drier soil (less conductivity)

Wiring:

  • VCC: 5V
  • AOUT: A2 (analog output)
  • GND: GND

Tasks

Task 1: Wire All Three Sensors

Wire all three sensors according to the specifications above. Use the breadboard to organize your connections.

Task 2: Read Sensor Values

Create an Arduino sketch that reads all three sensors and outputs their values to the Serial Monitor.

Example code structure:

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

void loop() {
  // Read temperature sensor
  int tempReading = analogRead(A0);
  float voltage = tempReading * (5.0 / 1023.0);
  float tempC = (voltage - 0.5) * 100.0;
  
  // Read light sensor
  int lightLevel = analogRead(A1);
  
  // Read moisture sensor
  int moisture = analogRead(A2);
  
  // Print values
  Serial.print("Temperature: ");
  Serial.print(tempC);
  Serial.print("°C | Light: ");
  Serial.print(lightLevel);
  Serial.print(" | Moisture: ");
  Serial.println(moisture);
  
  delay(1000);
}

Task 3: Conduct Experiments

For each sensor, conduct at least 2 experiments testing different conditions:

Temperature Sensor:

  • Test at room temperature
  • Hold sensor between fingers (body heat)
  • Place near ice or cold water
  • Any other temperature variations you can safely create

Light Sensor:

  • Measure in normal room light
  • Cover sensor completely (darkness)
  • Shine flashlight directly on sensor
  • Test under different lighting conditions

Moisture Sensor:

  • Test in air (completely dry)
  • Test in water (completely wet)
  • Test in damp soil or paper towel
  • Test at different moisture levels

Task 4: Document Your Findings

In your GitHub repository, create an experiments.md file documenting:

  • Your experimental setup
  • The conditions you tested
  • The sensor readings you observed
  • Any patterns or insights you discovered
  • Any challenges or issues you encountered

Task 5: Calibrate and Interpret

For each sensor, determine threshold values for different states:

  • Temperature: Cold, normal, warm
  • Light: Dark, dim, bright
  • Moisture: Dry, moist, wet

Deliverables

  1. Working circuit with all three sensors
  2. Arduino sketch that reads all sensors
  3. Serial Monitor output showing readings
  4. experiments.md file with your findings
  5. Demonstration to instructor by due date

Tips and Troubleshooting

  • Loose connections are the most common issue - make sure wires are firmly inserted
  • Check sensor orientation - many sensors have specific pin orders
  • Temperature readings jumping wildly? Check for loose wires
  • Light sensor not changing? Make sure you’re reading the AO pin, not DO
  • Moisture sensor gives constant values? Make sure the probes are clean and making contact

Assessment

This activity will be assessed based on:

  • ✓ Correct wiring of all sensors
  • ✓ Working code that reads all sensors
  • ✓ Quality of experiments conducted
  • ✓ Thoroughness of documentation
  • ✓ Successful demonstration

Resources