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Flame Sensor: Tips and Tricks You Should Know

Do you want to avoid fire outbreaks in your circuits, gas furnace, or heating equipment? Simple! You can install a flame sensor. Flame sensor circuits can detect and respond whenever there’s a fire outbreak. Plus, they respond to fire breakouts based on how you install them. 

Flame sensors can sound alarms, activate fire suppression systems, and even cut fuel lines.

So, keep reading this article to learn how a flame sensor works, how to replace a flame sensor, and how to build one yourself. 

How Does a Flame Sensor Work?

Flame sensors can save you from severe accidents like catastrophic explosions. It’s worse in hazardous areas where failure to detect fire outbreaks could wreak havoc on your equipment.

Flame sensors can get damaged from heat quickly, so installing a distance away from the potential fire source is best. However, this doesn’t decrease its effectiveness. In short, flame sensors are so sensitive to light that they can detect flames from a 100 cm distance with a detection angle of 600.

Also, some flame sensors detect flame wavelengths within a range of 760 nm to 1100 nm. At the same time, others can only operate within a maximum of 300 nm wavelengths.

Hence, every flame sensor works differently, so let’s look at how each works. 

Ultraviolet Flame Sensors

An ultraviolet flame sensor works within a maximum wavelength of 300 nm. Now, these flame sensors work by measuring the level of radiation in the air to detect flames or explosions within 3 – 4 milliseconds. Plus, a fire outbreak or explosion releases some extra radiation during ignition, which the sensor measures.

Infrared Flame Sensors

As the name implies, infrared flame sensors only work within the infrared spectral band. Plus, if there’s a flame, certain hot gasses will generate patterns in the Infrared region. 

Hence, the infrared flame sensor will analyze these patterns using a special thermal imaging camera. Thus, the entire process allows infrared flame sensors to detect explosions or flames.

Near IR Array Flame Sensors

Also called visual flame sensors, the near IR array flame sensors have advanced flame detection technology. 

The sensor uses a pixel array of a CCD to read near IR radiation and detect the presence of flames.

IR3 Flame Detection Sensors

Unlike the near IR array flame sensor, this flame sensor does not measure any background rotation. Instead, it measures the modulated elements of radiation. 

Thus, IR3 Flame sensors have more precise flame detections.

Moreover, these are only some of the types of flame sensors. Other types include ionization current flame sensors and thermocouple flame sensors. You can find thermocouple sensors in heating systems and gas-powered ovens. At the same time, ionization flame sensors work for industrial gas heaters.

Flame Sensor Arduino

In truth, you don’t need to build your flame sensors from scratch. You can always order one for your projects. Hence, this section will discuss how to interface your flame sensor with an Arduino. 

So, here are the materials you’ll need for this project:

  • Flame sensor (preferable one with an analog out)
  • Any source of flames for testing
  • Arduino board
  • Male to female jumper wires


Here are the steps you need to carry out this project successfully.

Step 1: Know the Type of Flame Sensors You Have

Before starting this project, you must understand your flame sensor products. 

Hence, we recommend using this project’s flame detector with an analog-out feature. Also, it should work for short-range fire sensing–usually up to 3 feet. Plus, the flame sensors should monitor projects and cut devices off when it detects a fire. 

  1. High sensitivity to IR wavelength at about 760 nm – 1100 nm light.
  2. It should have a real-time output voltage signal on its thermal resistance for its analog output (AO). Here are some other specifications:
  3. Its digital output (DO) should be a high-low signal generated when the temperature reaches the set limit. Also, you should be able to adjust the limit with a potentiometer.


  • Analog output (AO) pin
  • Digital output (DO) pin
  • Positive voltage input (VCC) pin (3.3 volts for digital and 5 volts for analog)
  • Ground (GND) pin

Step 2: Test and Troubleshoot Your Sensor

Check if your sensor works before connecting it to your Arduino. To do this, you require a flame light source for testing. 

First, connect your VCC to a power source (5v) and Ground pin. Next, take your flame source close to the sensors, preferably within one foot. It should light up the digital output LED.

Now, don’t worry if the DO-LED fails to light up. Check if you have a 5v power source, or if the flame is within range. You can also check if you connected the ground pin. Still not working? Then you have a faulty sensor.

Step 3: Wiring

Here, we need to wire the flame sensor to the Arduino. To achieve this, connect the flame sensors to the Arduino. Then, click the sensor’s pins to the Arduino’s pins. Hence, connect the VCC to the 5v pin, GND to GND, and AO to analog in 0.

Step 4: Arduino Code

Indeed, the Arduino code will map and read the analog values the flame sensor generates. The values can be anywhere from 0 – 1024. Using this code will make the flame sensor react in the following way:

When you hold the flame within 1.5 feet of the sensor, it will activate “case 0,” and it’ll send “**Close Fire**to the serial monitor. Now, if you hold the flame within 1.5 feet to 3 feet of the sensor, it’ll activate “case 1″ and send “**Distant Fire**” to the serial monitor. Additionally, if it doesn’t detect any flame, it’ll activate “case 2” and send “No fire” to the serial monitor.

The best part is; that the code constantly updates, so you can always get real-time feedback from the flame sensor. Here’s the code:

Arduino Code

Arduino Code 

Flame Sensor Replacement

Like every other electrical device, Flame sensors can wear out over time and fail to get accurate flame detections.

The truth is; that replacing a flame sensor for your circuits or devices is easy. You’d need to take different actions if you’re replacing the furnace sensor; buy another flame sensor and repeat the steps above to set it up. After purchasing your replacement flame sensors, open the access cover of your furnace and remove your old flame sensors. Afterward, install the new flame sensor and ensure everything is connected correctly.

Additionally, ensure the replacement is compatible with your circuit or furnace to avoid wasting time and money.

Flame Sensor Troubleshooting

If your flame sensors don’t work correctly, you can easily carry out a little troubleshooting. You can follow the troubleshooting steps we mentioned above for your stock flame sensors. However, if you have furnace flame sensors, you can clean the soot of the sensor’s tip if it’s a dirty flame sensor or service it if the information is black.

When Should You Replace Your Flame Sensor?

It’s not safe to wait for your worn-out flame sensors to misbehave before changing them. Failure to detect a flame early could cause a lot of disasters. So, you should regularly maintain your flame sensors and replace them periodically. In short, flame sensors can last up to five years. But, we recommend that you return it within two years for better performance.

Final Thoughts

A Flame sensor is an important safety device when dealing with gas-powered or heating applications. These applications are more prone to fire accidents and explosions. And flame sensors can help you detect unforeseen circumstances.

Furnace sensors are different from stock flame sensors. So, be sure to get the sensor that matches your project. Also, the type of flame sensors you’ll need depends on your application.

Have any questions regarding flame sensors? Be sure to contact us, and we’ll be happy to help.

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Emma Lu
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