Arduino MKR WiFi 1010 - Flame Sensor

Hardware Preparation

Or you can buy the following kits:

Overview of Flame Sensor

What is a Flame Sensor?

A flame sensor (also called infrared flame sensor, fire sensor, or IR flame detector) is a sensor designed to detect the presence of fire by sensing the infrared radiation emitted by flames.

How Flame Sensors Work:

• Flames emit infrared (IR) radiation in the wavelength range of 760-1100nm
• Flame sensors contain IR photodiodes or phototransistors sensitive to this range
• The sensor detects IR radiation and converts it to electrical signals
• Built-in comparator converts analog signal to digital output

Why Use Flame Sensors?

• Fast response: Detects flames instantly (faster than smoke detectors)
• Direct fire detection: Responds to actual flames, not just heat or smoke
• Dual outputs: Provides both digital (detected/not detected) and analog (intensity) signals
• Adjustable sensitivity: Built-in potentiometer allows threshold adjustment
• Wide detection angle: Typically 60-degree cone of detection
• Cost-effective: Inexpensive solution for fire detection projects

Important Limitations:

• False positives possible: Can be triggered by sunlight, hot objects, or other IR sources
• False negatives possible: May miss fires if flames are blocked or outside detection range
• Line-of-sight required: Cannot detect fire through walls or obstacles
• Limited range: Effective detection typically 0.8-1.5 meters
• Not a safety device: Suitable for projects but not certified for life-safety applications

Common Applications:

• Fire alarm and detection systems
• Automatic fire suppression triggers
• Robot fire-fighting competitions
• Industrial furnace monitoring
• Stove and burner flame monitoring
• Laboratory safety systems
• Educational fire detection projects

Flame Sensor Outputs

Flame sensors provide two types of outputs that can be used independently or together:

1. Digital Output (DO Pin):

• Simple fire detection: HIGH when no flame, LOW when flame detected
• Adjustable threshold: Use built-in potentiometer to set sensitivity
• LED indicator: Built-in LED shows detection status
• Perfect for: Alarms, binary detection, triggering actions

2. Analog Output (AO Pin):

• Flame intensity measurement: Value increases with stronger IR radiation
• Variable readings: Typically 0-1023 range on Arduino
• Distance sensing: Higher values when closer to flame
• Perfect for: Measuring flame strength, distance estimation, gradual responses

Pinout

Flame sensors come in two common configurations:

Available Modules:

• Single Flame Sensor Module: One directional sensor
• 5-in-1 5-way Detection Flame Sensor Module: Five sensors in different directions

Single Flame Sensor Pinout

A standard single flame sensor module has four pins:

Power Pins:

• VCC pin: Connect to power supply (3.3V or 5V)
• 5V recommended for best performance
• Module includes voltage regulator
• GND pin: Connect to ground (0V)
• Common ground with Arduino

Output Pins:

• DO pin (Digital Output): Digital flame detection signal
• HIGH: No flame detected (pulled up internally)
• LOW: Flame detected (above threshold)
• Threshold adjustable via potentiometer
• Can connect directly to Arduino digital input
• AO pin (Analog Output): Analog IR intensity signal
• Higher values: Stronger IR radiation (closer/bigger flame)
• Lower values: Weaker IR radiation (farther/smaller flame)
• Range: 0-1023 on Arduino (10-bit ADC)
• Not affected by potentiometer adjustment

LED Indicators:

Most flame sensor modules include two LEDs:

• Power LED (usually red):
• Lights up when module is powered
• Indicates module is receiving power
• Always on when VCC connected
• Status LED (usually green/blue):
• Connected to DO pin
• Lights up when flame detected (DO goes LOW)
• Visual confirmation of detection
• Helps during sensitivity adjustment

Potentiometer (Sensitivity Adjustment):

• Small blue or white adjustment screw on module
• Turn clockwise: Decrease sensitivity (requires stronger/closer flame)
• Turn counterclockwise: Increase sensitivity (detects weaker/farther flames)
• Affects DO pin threshold only (AO pin unaffected)
• Test and adjust while pointing at flame

5-in-1 Flame Sensor Configuration

The 5-in-1 module combines five flame sensors on one board:

Shared Components:

• One potentiometer controls all five sensors
• Common VCC and GND connections
• Power LED indicator

Individual Components (per sensor):

• Separate DO pin (5 total)
• Separate AO pin (5 total)
• Each sensor faces different direction
• Independent detection for each angle

Advantages:

• 360-degree coverage (when mounted properly)
• Redundancy - multiple sensors reduce false negatives
• Directional fire localization
• Perfect for robot fire-fighting applications

How It Works

Digital Output (DO Pin) Operation

The digital output provides simple YES/NO flame detection:

Internal Comparator Circuit:

1. Flame sensor continuously measures IR radiation
2. Converts IR intensity to analog voltage
3. Compares voltage against threshold set by potentiometer
4. Outputs digital signal based on comparison

Detection States:

No Flame Detected: IR Level < Threshold → DO Pin: HIGH → Status LED: OFF → Arduino reads: HIGH Flame Detected: IR Level ≥ Threshold → DO Pin: LOW → Status LED: ON → Arduino reads: LOW

Sensitivity Adjustment Process:

1. Power on the module
2. Point sensor at target flame (at desired detection distance)
3. Adjust potentiometer while watching status LED:

- Turn clockwise if LED doesn't light (increase threshold - less sensitive)

- Turn counterclockwise if LED lights too easily (decrease threshold - more sensitive)

1. Test at various distances and flame sizes
2. Fine-tune until detection range matches requirements

Important Notes:

• Potentiometer adjustment only affects DO pin
• AO pin remains unaffected by potentiometer
• Over-sensitivity causes false positives (sunlight, heat sources)
• Under-sensitivity causes missed detections

Analog Output (AO Pin) Operation

The analog output provides flame intensity measurement:

Behavior:

• High IR radiation (strong/close flame) → High analog value (close to 1023)
• Low IR radiation (weak/far flame) → Low analog value (close to 0)
• No flame → Low baseline value (typically 50-200)

Typical Value Ranges:

Scenario Approximate AO Value ───────────────────────────────────────────── No flame (room light) 50-150 Flame 1.5m away 200-400 Flame 1.0m away 400-600 Flame 0.5m away 600-800 Flame very close (<20cm) 800-1000

Use Cases for Analog Output:

• Distance estimation: Approximate distance to flame
• Flame strength: Measure fire intensity
• Gradual response: Adjust fan speed based on flame proximity
• Multiple thresholds: Different actions for different intensities
• Data logging: Record flame intensity over time

Key Insight:

The potentiometer does not affect the AO pin. If you need adjustable analog thresholds, implement them in your Arduino code, not via the potentiometer.

Wiring Diagram

The flame sensor module provides two outputs (DO and AO). You can use either one or both depending on your project requirements.

This configuration uses both DO and AO pins for complete flame detection and intensity measurement:

This image is created using Fritzing. Click to enlarge image

Connections:

• Flame Sensor VCC → Arduino 5V
• Provides power to sensor module
• 5V recommended for optimal performance
• Flame Sensor GND → Arduino GND
• Common ground connection
• Flame Sensor DO → Arduino D2 (digital input)
• Digital flame detection signal
• Configure as INPUT in code
• Flame Sensor AO → Arduino A0 (analog input)
• Analog flame intensity signal
• Read with analogRead() function

When to Use Digital Only:

• Simple fire alarm (detected/not detected)
• Triggering relay or buzzer
• Binary fire detection
• Fewer Arduino pins needed

When to Use Analog Only:

• Measuring flame intensity
• Distance-based responses
• Gradual flame strength monitoring
• Custom threshold in software

When to Use Both Outputs:

• Need both detection confirmation and intensity measurement
• Want to compare digital threshold with analog value
• Testing and calibration purposes
• Advanced fire detection algorithms

Wiring Tips:

• Sensor orientation: Point IR detector toward expected flame location
• Mounting: Use stable mount to prevent vibration affecting readings
• Distance: Keep wires short (under 50cm) to minimize noise
• Testing: Test with real flame (candle, lighter) during setup
• Safety: Never leave flame unattended during testing

Power Supply:

For This Project: Simply plug your Arduino MKR WiFi 1010 into your computer's USB port. The flame sensor module draws minimal current (<50mA), well within USB power limits.

Arduino MKR WiFi 1010 Code - Read Value from DO Pin

This first example uses the digital output for simple flame detection. Perfect for fire alarms, automated suppression triggers, or any application requiring YES/NO flame detection.

What the Code Does:

• Configures digital pin D2 as input for flame sensor DO pin
• Continuously reads digital state (HIGH = no flame, LOW = flame detected)
• Displays clear "DETECTED" or "NOT DETECTED" messages
• Updates readings every 500ms for real-time monitoring
• Simple binary detection - no analog complexity

Code Explanation - Digital Detection

Pin Configuration:

Configures D2 as digital input. No pull-up needed - flame sensor has active output driver.

Reading Digital State:

Reads current DO pin state:

• LOW: Flame detected (IR level above threshold)
• HIGH: No flame detected (IR level below threshold)

Interpreting Results:

Important: LOW means detected (inverse logic due to sensor design).

Practical Applications:

1. Fire Alarm:

2. Automatic Suppression:

3. Safety Cutoff:

Detailed Instructions

New to Arduino MKR WiFi 1010? Complete our Getting Started with Arduino MKR WiFi 1010 tutorial first to set up your development environment.

Step 1: Hardware Setup

• Connect flame sensor to Arduino MKR WiFi 1010 following wiring diagram:
• VCC to 5V
• GND to GND
• DO to D2
• Mount sensor pointing toward test area

Step 2: Connect and Configure

• Use USB cable to connect Arduino MKR WiFi 1010 to your computer
• Launch Arduino IDE
• Select Arduino MKR WiFi 1010 board and COM port

Step 3: Upload Code

• Copy the code above
• Open in Arduino IDE
• Click Upload button
• Wait for "Done uploading" message

Step 4: Adjust Sensitivity

• Open Serial Monitor (baud rate: 9600)
• Light a candle or use lighter
• Place flame about 30-50cm from sensor
• Observe Serial Monitor:
• If flame not detected, turn potentiometer counterclockwise (increase sensitivity)
• If false positives occur, turn potentiometer clockwise (decrease sensitivity)
• Find optimal setting where flame reliably detected at desired distance

Step 5: Test Flame Detection

• Point sensor at flame - should see "DETECTED" messages
• Remove flame - should see "NOT DETECTED" messages
• Watch status LED on sensor module (lights when flame detected)
• Test at various distances to verify detection range

Expected Serial Monitor Output:

Sensitivity Adjustment Tips:

• LED stays on constantly: Too sensitive - turn clockwise
• LED never lights: Not sensitive enough - turn counterclockwise
• Intermittent false triggers: Reduce sensitivity or shield from sunlight
• Optimal setting: Detects flame at desired distance without false positives

Arduino MKR WiFi 1010 Code - Read Value from AO Pin

This second example uses the analog output to measure flame intensity. Perfect for distance estimation, gradual responses, or analyzing flame characteristics.

What the Code Does:

• Configures analog pin A0 as input for flame sensor AO pin
• Continuously reads analog value (0-1023 range)
• Displays raw analog readings for analysis
• Higher values indicate stronger IR radiation (closer/bigger flame)
• Updates readings every 200ms for smooth data flow
• Potentiometer adjustment does NOT affect these readings

Code Explanation - Analog Intensity Measurement

Reading Analog Value:

Reads 10-bit ADC value (0-1023):

• Low values (0-200): No flame or very distant
• Medium values (200-600): Flame detected at moderate distance
• High values (600-1023): Strong flame or very close

Understanding the Values:

Practical Applications:

1. Distance-Based Response:

2. Variable Fan Speed:

3. Fire-Fighting Robot:

4. Data Logging:

Detailed Instructions

New to Arduino MKR WiFi 1010? Complete our Getting Started with Arduino MKR WiFi 1010 tutorial first to set up your development environment.

Step 1: Hardware Setup

• Connect flame sensor to Arduino MKR WiFi 1010:
• VCC to 5V
• GND to GND
• AO to A0 (analog input)
• Position sensor pointing toward test area

Step 2: Upload and Test

• Copy the code above into Arduino IDE
• Select Arduino MKR WiFi 1010 board and COM port
• Click Upload button
• Open Serial Monitor (baud rate: 9600)

Step 3: Observe Analog Values

• With no flame, note baseline value (typically 50-200)
• Light a candle
• Slowly move flame closer to sensor
• Watch values increase as flame gets closer
• Move flame away and watch values decrease

Expected Serial Monitor Output:

Understanding Your Readings:

• Low consistent values (50-200): No flame present
• Sudden increase (300+): Flame entering detection range
• High values (700-1000): Flame very close
• Gradual decrease: Flame moving away
• Fluctuating values: Normal - flames are dynamic

Calibration Tips:

• Note maximum value at desired detection distance
• Set software threshold slightly below maximum
• Test with different flame sizes (candle vs lighter)
• Account for ambient IR sources (sunlight)
• Remember: Potentiometer does NOT affect analog readings

Troubleshooting Common Issues

Problem: Sensor Always Detects Flame (DO LED Always On)

Possible Causes:

• Potentiometer set too sensitive
• Strong ambient IR sources (sunlight, hot objects)
• Sensor pointing at heat source
• Faulty sensor module

Solutions:

1. Turn potentiometer clockwise to decrease sensitivity
2. Shield sensor from direct sunlight
3. Point sensor away from hot surfaces (computers, lamps)
4. Test in controlled lighting conditions
5. Verify sensor in dark room first

Problem: Sensor Never Detects Flame

Possible Causes:

• Potentiometer set not sensitive enough
• Flame outside detection range (>1.5m)
• Sensor not pointed at flame
• Wiring error
• Dead sensor

Solutions:

1. Turn potentiometer counterclockwise to increase sensitivity
2. Move sensor closer to flame (30-50cm)
3. Check sensor orientation - IR detector faces flame
4. Verify wiring: VCC to 5V, GND to GND, DO to D2
5. Test DO pin voltage with multimeter
6. Try different flame sensor module

Problem: Analog Values Always Read Low (~50-150)

Possible Causes:

• AO pin not connected properly
• Wrong pin in code
• Sensor not powered
• Faulty AO circuit

Solutions:

1. Verify AO pin connected to A0 on Arduino
2. Check code: analogRead(A0) matches your wiring
3. Confirm VCC and GND connected
4. Test sensor with known-good flame (candle)
5. Try different analog pin and update code

Problem: Erratic or Noisy Readings

Possible Causes:

• Electrical interference
• Long or poor quality wires
• Unstable power supply
• Ambient IR fluctuations

Solutions:

1. Use shorter wires (<30cm) between sensor and Arduino
2. Add 100μF capacitor between VCC and GND (near sensor)
3. Average multiple readings in code:

1. Shield wires from motors and power lines
2. Use filtered power supply

Problem: False Positives from Sunlight

Cause: Sunlight contains IR radiation that triggers sensor.

Solutions:

1. Shield sensor from direct sunlight
2. Reduce sensitivity with potentiometer
3. Mount sensor indoors away from windows
4. Add IR filter in front of sensor (flame wavelengths only)
5. Use dual confirmation (multiple sensors)

Problem: DO and AO Give Conflicting Results

Cause: Potentiometer threshold doesn't match your analog threshold in code.

Solution: Remember that potentiometer only affects DO pin. Set thresholds independently:

• DO threshold: Adjust with potentiometer
• AO threshold: Set in code based on observed values

Challenge Yourself - Creative Extensions

Once you have the basic flame sensor working, try these enhancements:

1. Complete Fire Alarm System

Combine flame sensor with buzzer and LED:

2. WiFi Fire Alert Notifications

Send alerts to your phone using Arduino MKR WiFi 1010's WiFi:

3. Automatic Fire Suppression

Activate water pump or CO2 system:

4. Multi-Zone Fire Detection

Monitor multiple rooms with multiple sensors:

5. Fire-Fighting Robot

Create autonomous fire-fighting robot:

6. LCD Fire Status Display

Show detection status on LCD:

7. Temperature-Compensated Detection

Combine with temperature sensor for better accuracy:

8. Data Logging to SD Card

Log all flame events with timestamps:

9. Safety Interlock System

Prevent false activations with confirmation delay:

10. Integration with Home Automation

Control home systems based on fire detection:

Experiment and learn - but always prioritize safety!

Video Tutorial

Function References

• pinMode()
• digitalRead()
• analogRead()
• Serial

Learn More