Light sensor in Xiaomi smartphones: where to look and how to check the performance

Have you ever noticed how your Xiaomi screen automatically adjusts brightness to ambient light? A tiny but critical component, the light sensor, is responsible for this function, but when it fails or gets polluted, users run into problems: The screen gets too dark in sunny weather or blinds your eyes at night. In this article, we will not only show you where the light sensor in Xiaomi smartphones (including Redmi models) is located, POCO and flagship series), but also teach to diagnose its malfunctions without disassembling the device.

The manufacturer rarely indicates the exact location of the sensor in the documentation, and its miniature size (usually the sensor is not specified in the document). 2×2 It makes the search visually difficult. We've collected data from the 30+ Xiaomi models (2018–2026 We analyzed the dispersion schemes and interviewed the masters of service centers to compile a universal map of the location of the sensor for all popular lines. You will also learn how to distinguish it from a front-facing camera or infrared port, and what to do if the sensor stops working after a fall or upgrade. MIUI.

What does the light sensor look like and what it is responsible for

The light sensor (Ambient Light Sensor, ALS) — It's an optoelectronic component that converts the intensity of ambient light into an electrical signal. In Xiaomi smartphones, it performs three key functions:

• 🔄 Automatic adjustment of screen brightness (adaptive brightness) - adjusts the backlight to lighting conditions, saving battery power.
• 🌓 Activation of the "Dark theme" mode - includes night mode in low light (starting with the MIUI 11).
• 📱 Color temperature adjustment – In some models (such as Xiaomi 13 Ultra), the sensor helps adjust white balance for comfortable reading.

The sensor is externally:

• 🔍 Tiny round or oval opening (diameter) ~1 mm) next to the front camera, often disguised as a decorative netting.
• 📏 Black or dark grey square on the board (the size of a grain of rice) when disassembling the device.
• 💡 Transparent or semi-transparent filter – some models (e.g, POCO F5) have a protective glass over the sensor.

It's important not to confuse it with other sensors: The infrared port (for the remote control) is usually symmetrically located on the right and has a reddish hue when turned on. The proximity sensor is hidden under the screen and not visible from the outside - it is responsible for turning off the display during a call.

The exact location of the sensor in popular Xiaomi models

The location of the light sensor depends on the design of the front panel and the generation of the smartphone. We have organized the data by the main rulers in the table below. Note that in models with a cut-out for the camera (" bang"), the sensor is always on the left of the front camera, and in devices with a hole display - under the screen, next to the top bezel.

For models with AMOLED-screens (e.g. Xiaomi) 12T or POCO F4 GT) The sensor is often integrated into the matrix, and it's not visible indiscriminately:

# #6484## - Light sensor test (shows current values in luxes)
#4636## → “Phone Information” → “Sensors”

Why the light sensor may not work: top-5 cause

If the automatic brightness control has stopped working, the problem is not always with the sensor itself.

1. Dust, greasy prints or remnants of a protective film block the light from entering. Redmi Note 10 Pro and POCO X3 NFC This is especially true because of the sensor’s open location. ⚠️ Warning: Do not use alcohol or abrasive wipes to clean - this will damage the anti-reflective coating of the sensor. Take a soft brush (for example, for camera lenses) and carefully remove dust.
2. Software failure after update MIUI Update to MIUI 13/14 Sometimes they reset the sensor settings. → Display. → Brightness → Automatic adjustment (enable) If the slider is inactive - reset the screen settings to factory (Settings) → System system → Resetting settings → Resetting display settings).
3. A smartphone drop can displace the sensor plume or damage its contacts on the motherboard, symptoms: the brightness "jumps" or fixes at the same level, in which case only diagnostics at the service center with a check of the sensor's power chain will help.

Less obvious reasons:

• 🔋 Discharged battery – at a charge level below 15%, the system turns off “extra” sensors to save energy.
• 🛡️ Third-party shells (like Nova Launcher) can block access to sensors.

Check the automatic brightness settings|Clean the sensor hole with a soft brush|Reboot your smartphone|Test the sensor through the engineering menu|Make sure the battery is more than 20 times charged%-->

How to clean the light sensor yourself

If the problem is pollution, you can clean the house without disassembling the device.

• 🖌️ Soft brush (for cleaning lenses or makeup).
• 💨 A compressed air canister (optional, for blowing out dust).
• 🔦 Flashlight – to illuminate the sensor at an angle.
• 🧴 Microfiber wipe (not containing alcohol!).

Step-by-step:

1. Turn off your smartphone to avoid false sensor alerts.
2. Point the flashlight at the sensor area (see table above) – the contamination will be visible as dark spots.
3. Carefully swipe the brush through the hole without pressing. POCO F5) Use compressed air from a distance of 10 cm.
4. Wipe the top screen frame with a napkin to remove greasy marks.
5. Turn on your phone and check the sensor through the test code ##6484###.

⚠️ Warning: Do not use toothpicks, needles or cotton swabs, they can scratch the sensor or shift its position. If the sensor does not work after cleaning, there is a likely hardware malfunction (a plume break or a chip failure).

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For models with an under-screen sensor (such as the Xiaomi 13 Lite), cleaning is not possible indiscriminately, in which case only a professional ultrasonic bath in the service center will help.

What to do if the light sensor is broken: repair or replacement

If the diagnostics show that the sensor is not responsive to light, you have three options:

More about each method:

1. Flashing MIUI

Sometimes the sensor stops working after the update due to driver conflict.

• Reverse to the previous version of MIUI via Fastboot.
• Install custom recovery (for example, TWRP) and sew clean firmware.

For this, download the official ROM From Xiaomi and follow the instructions for your model.

2. Replacement at the service center

If the sensor is physically damaged, it's replaced with a new one.

• 📱 Redmi Note 11 — 1 800 ₽.
• 📱 Xiaomi 12 Pro — 2 500 ₽ (owing to the complexity of the).
• 📱 POCO F4 GT — 2 200 ₽ (sensor integrated into the camera module).

3. Self-repair

For power users, you can buy the light sensor on AliExpress (search using a model, for example, "Xiaomi Redmi Note 10 Pro light sensor") and replace it yourself.

• 🔧 Setting screwdrivers T3–T5.
• 🔥 A blow dryer (for welding the plume off).
• 🧲 Screen suction cup.

⚠️ Attention: In Xiaomi models 13/14 The sensor is soldered to the motherboard in a series, and it needs to be reflashed. EEPROM after soldering, otherwise the sensor will not be recognized by the system.

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Before repairing, check whether your smartphone is not valid warranty Xiaomi. in this case, self-examination will cancel it, and official repairs will cost less (or free in the case of industrial defects).

Xiaomi models with frequent light sensor problems

Analysis of user complaints in forums 4PDA, Mi Community and service center data have shown that some Xiaomi models are particularly prone to sensor malfunctions.-5 "Problem devices include:

1. Redmi Note 9 Pro (2020) Reason: design defect - the sensor is too close to the edge of the case, causing it to get moisture and dust.
2. POCO X3 NFC (2020 Cause: weak contact of sensor plume with motherboard, often fails after falls.
3. Xiaomi Mi 10T / 10T Pro (2020) Reason: Overheating due to the powerful Snapdragon 865 processor causes sensor malfunctions.
4. Redmi A1 / A1+ (2022: Cheap sensor with no protection against static electricity, often fails after battery discharge to zero.
5. Xiaomi 12 Lite (2022) The reason: poor calibration in the factory. The sensor shows understated values of the luxury, which makes the screen always too dark.

For the Redmi Note 9 Pro and POCO X3 NFC Xiaomi has released a correction in MIUI 12.5, but it doesn't help everyone. If your smartphone is on this list, we recommend it:

• 🔄 Update to the latest version of the firmware.
• 🛠️ Contact the service for soldering of the sensor (if the warranty has expired).
• 📵 Turn off automatic brightness and use manual tuning through the widget.

How to turn off the light sensor (if it interferes)

In some cases, users prefer to turn off automatic brightness control:

• 🎮 For gamers – to avoid jumps in brightness during the game.
• 👓 For people with sensitive eyes, if the sensor is not working properly.
• 🔋 To save charge – automatic adjustment consumes up to 5% of the battery per day.

Methods of shutdown:

Method 1. Through settings MIUI

Settings → Display → Brightness → Disable “Automatic adjustment”

In some firmware (for example, MIUI 14 for Xiaomi 13) this item is hidden:

Settings → Special features → Display settings → Automatic brightness (disable)

Method 2. ADB (power-user)

If the switch off point is not in the menu, use the command:

adb shell settings put system screen_brightness_mode 0

To return automatic adjustment, replace 0 with 1.

Method 3. Applications for fine-tuning

Utilities like QuickShortcutMaker or MacroDroid allow you to create shortcuts to quickly switch brightness mode.

1. Install MacroDroid from Google Play.
2. Create a macro with the trigger "Double press statusbar".
3. Add the action "Change system settings" → "Brightness mode" → "Hand-held".

⚠️ Note: On some models (for example, Redmi Note 12) to turn off the light sensor through the ADB It causes a malfunction in the screen calibration, and then you can only reset the settings to the factory.

FAQ: Frequent questions about the light sensor in Xiaomi