Sensor on the case Xiaomi: what kind of sensor, how it works and why you need

If you’ve ever noticed a small round or oval hole on the back of a Xiaomi smartphone, Redmi or a sleek, sleek, or sleek look at it. POCO, Now, you've probably wondered, what kind of sensor is it, why is it needed? It's a very confusing element, which is often mistaken for a microphone, a speaker, or even a decorative plug. It's actually a proximity/light sensor that performs several important functions.

In this article, we'll go into detail about what the sensor is, how it's built, why it's placed on the back of the case, and what to do if it doesn't work properly, and whether it can be turned off, how to check for serviceability, and which Xiaomi models have these sensors, and if you notice that the phone is acting strangely -- for example, the screen goes out for no reason or automatically adjusts brightness -- this small but important element may be to blame.

What is the sensor on the case Xiaomi and where it is located

On most Xiaomi smartphones (especially in the Redmi Note lineups, POCO X and Mi) on the back next to the main camera or flashlight, you can see a small hole with a diameter of 1-2 mm:

• 🔦 Automatic adjustment of screen brightness depending on ambient light.
• 📱 Turning off the screen during a phone conversation when you bring the device to your ear.
• 🔋 Optimizing energy consumption through adaptive lighting.
• 🎮 Signs in certain games and applications (e.g., in PUBG Mobile or Genshin Impact).

Unlike front-facing sensors (which are located next to a selfie camera), the rear sensor is used primarily for additional calibration, for example, it helps to determine whether the phone is lying down on the table with the screen so as not to turn on the display when notifications arrive.

Where exactly do you look for this sensor? It depends on the model.

• 📱 Redmi Note 10/11/12, POCO X3/X4/X5 — right-hand.
• 📱 Xiaomi 11T/12T/13 — under the flash or near an ultra-wide camera.
• 📱 Redmi 9/9A/9C — top-left corner of the back panel.

How the proximity and illumination sensor works in Xiaomi

Rear sensor in Xiaomi smartphones is not a separate element, but part of the infrared system (IR) sensors that include:

1. Infrared emitter sends an invisible signal and analyzes the reflected light.
2. Photodiode - captures changes in the intensity of light.
3. Microcontroller – processes data and sends commands to the system.

Example of work:

• 📞 When you hold your phone to your ear during a call, the infrared beam bounces off the surface and the sensor picks up the approach.
• ☀️ In bright sunlight, the illumination sensor increases the brightness of the display, and in a dark room - reduces, saving battery power.

Interesting fact: In some models (such as the Xiaomi Mi 11 Ultra), this sensor is also used to recognize gestures in the air – for example, to flip through photos or control music without touching the screen.

Why Xiaomi moved the sensor to the back panel

Previously, proximity and light sensors were only placed on the front of the selfie camera, but in recent Xiaomi models, they began to be duplicated or transferred to the back. Why?

• 📏 Reduce the screen frames. Modern smartphones are striving for frameless design, and the space for front-facing sensors is shrinking.
• 🔄 Backup. If the front sensor fails, the back sensor will take over some of the functions.
• 🎮 In games like Call of Duty Mobile or Free Fire, the sensor on the back allows you to control the character without blocking the screen with your fingers.
• 🔋 Energy optimization: The back light sensor can tell you more precisely when the phone is down, and it turns off unnecessary processes.

In addition, in some models (such as the Xiaomi Mix 4), the rear sensor is used to recognize faces in an alternative mode – if the main front camera is occupied or closed.

⚠️ Note: If your Xiaomi smartphone doesn't respond to your hand approaching during a call or doesn't adjust brightness automatically, the problem may be contamination of the sensor.

How to check the sensor on Xiaomi

If you suspect that the proximity or illumination sensor is not working properly, you can test it without any special tools.

1. Open the Phone app and dial ##6484## (test mode) MIUI)

2. Select Proximity Sensor (approximation sensor)

3. Raise your hand to the back panel - the value should change from 5 (far) to 0 (close)

4. To check for light, go to the Light Sensor and point the phone to the light source.-->

If the test shows incorrect values:

• 🧹 Clean the sensor hole with a soft brush or compressed air.
• 🔄 Restart your phone – sometimes the crash is due to a software glitch.
• 📱 Reset sensor settings in Settings → System system → Resetting settings → Resetting sensor settings.

If the sensor doesn't respond at all, it may be physically damaged (for example, after a fall) or turned off in the firmware, in which case only repair or flashing will help.

💡

To quickly check autobrightness, go to Settings → Display. → Automatic brightness and turn on/off option.If the screen does not respond to changing lighting, sensor malfunctions.

Can you turn off the sensor on Xiaomi and how to do it?

Some users want to disable the proximity or illumination sensor because it:

• 🔄 Interferes with calls (screen does not turn on when needed).
• ☀️ Incorrectly adjusts brightness (too dim or too bright).
• 🎮 Conflicts with games (false gestures).

Unfortunately, in the standard settings MIUI There's no separate switch for the back sensor, but there are workarounds:

1. Turn off autobrightness: Settings → Display. → Automatic brightness → Turn off This deactivates the light sensor, but the proximity sensor will continue to work.
2. Use Engineering Mode (power users only!): 1. Type ##3644633# (Engineering Mode) 2. Go to Hardware Testing → Sensor → Proximity Sensor 3. Select Disable (Disable) ⚠️ Warning: Incorrect actions on the engineering menu can lead to a loss of warranty or software failure.Do this at your own risk!
3. Install custom firmware (e.g. Pixel Experience or LineageOS) where sensors can be flexibly configured.

If you need to turn off the sensor only for specific applications (such as games), use the Resolution settings. → Sensors in MIUI 14+.

Frequent Sensor Problems on Xiaomi and How to Fix Them

Users often face the following problems:

If none of these things worked, maybe the problem is the hardware failure.

• 🛠️ Contact the official Xiaomi service center.
• 🔧 Check your phone for moisture or mechanical damage (especially after falls).
• 📦 If the warranty is valid, do not attempt to repair yourself!

💡

In 90% of cases, the sensor problems on Xiaomi are solved software – just clean it, reset the settings or update the firmware.

Xiaomi models with rear sensor: the full list

Not all Xiaomi smartphones have a sensor on the back, and here is the current list of models (as of 2026) where it is exactly:

• 📱 Xiaomi 13/13 Pro/13 Ultra - proximity sensor + lighting.
• 📱 Redmi Note 12 Pro+/12 Pro/12S — infrared sensor.
• 📱 POCO F5/F5 Pro/F4 GT — game-probe.
• 📱 Xiaomi 12T/12T Pro/12 Lite - lighting + near-point.
• 📱 Redmi K50/K50 Pro/K50 Gaming – Extended Gaming Features.
• 📱 Xiaomi Mix 4/Mix Fold 2 — folder-screen.

In budget models (e.g. Redmi) 10A or POCO M5) There is usually no back sensor – only front-facing sensors are used.

To find out if there is a sensor on your model, check:

1. Official specifications on the Xiaomi website.
2. Test mode (#6484##)
3. Disassembly on YouTube (e.g., Zack Nelson or TechDroider).

FAQ: Frequent questions about the sensor on Xiaomi