📡 How Infrared Sensors Work in Automatic Faucets and Automatic Flush Valves: Why Does the “Color of the Object” Affect?

Hygienic Automatic Device
Jul 18
2 min read

Automatic faucets and automatic flush valves work with an “infrared sensor” system that can detect movement or objects within a specified range. When a hand approaches that range, the system will automatically turn on the water.

But did you know that…

The color of objects approaching the sensor also affects the system's operation?

In particular, “black” and “white” reflect light differently.

🎯 How infrared sensors work

Infrared sensors in automatic faucets and automatic flush valves work by emitting infrared light in front of the sensor.

If an object is in range, such as the user's hand or body (in the case of automatic flush valves), the light will reflect back to the sensor receiver and command the faucet or flush valve to open the water.

📌 Important: The system will work only when the “sensor detects reflected light”.

⚠ Problem: Black objects are often harder to detect than other colors. Why?

due to:

Black objects absorb more light than they reflect.
This causes the emitted infrared light to reflect back less , or sometimes not reaching the receiving point at all.
As a result, the sensor may “not work” or “work slowly” when encountering a dark object, such as a dark-colored hand or black shirt.

✅ White objects = easy to detect

White has the property of reflecting light very well.
Infrared light is therefore clearly reflected back.
The sensor faucet or flush valve will respond quickly and accurately.

🔧 How to fix if you encounter a problem with the sensor not responding

problem	Solution
Black objects, such as black clothes, very dark hands	Move your hand or body closer to the sensor, or change the angle of your hand to better reflect the light.
The sensor distance is set too close.	Increase the detection range (for adjustable models)
The sensor is dirty or blurry.	Use a soft cloth to gently wipe the sensor surface. Do not use a hard cloth as it will scratch the sensor and cause malfunction.
Ambient light disturbance	Avoid strong light sources such as direct sunlight near the sensor.

💡 More tips for installing faucets and sensor flush valves to work accurately

Install in a location where there are no moving objects near the sensor at all times.
Avoid installing in areas with strong sunlight or direct exposure.
Choose a sensor model with Auto Compensation to use in all environments.