Modern smartphones like the Xiaomi Redmi 8 feature a host of hidden sensors that provide a comfortable interaction with the device. One key element is the proximity sensor, which automatically extinguishes the screen during a conversation, preventing accidental cheek pressing. Understanding where exactly it is located is critical for the proper operation of the gadget and the glue of protective glasses.
Many users experience a screen that doesn't go out or light up after a call is over, often due to a misunderstanding of the sensor's area of operation or contamination of the top of the case, and in this article, we'll take a closer look at the sensor's physical location, how it's checked and how it's set up to work smoothly.
Owners of Xiaomi Redmi 8 need to know that the design of the front panel has its own features that distinguish this model from the flagship lines. Ignoring these nuances can lead to the fact that even a high-quality protective film will block the sensitive element, making calls impossible without the use of hands-free communication.
Physical location of the sensor on the body
On the Redmi 8, engineers used a classic layout to place components at the top of the front panel, a proximity sensor hidden under a black bar above the display, next to the speaker. Unlike some other models, there is no separate visible hole; the sensor is integrated into a single panel along with the event indicator.
The exact location of the sensor is often controversial because it's not visible visually, and the infrared emitter and receiver are on the right side of the top black bezel, as you look at the screen from the front, and that's where the signals are exchanged to determine the distance to the object.
It is important to consider that the design of the Xiaomi case involves working through glass. If you use a protective glass with a wide black bezel or poor transparency at the top, this can block the signal.
⚠️ Warning: When sticking the protective glass, make sure it does not overlap the top right of the black frame above the display, otherwise the sensor will not work properly.
To accurately determine the zone, you can use a flashlight by directing the beam at an angle to the top of the screen when the display is off - sometimes you can notice a slight glow or glare from the internal component, which will indicate its location.
The principle of operation of the infrared sensor
The technology used in Redmi 8 is based on infrared radiation, and the sensor is made up of two parts: a emitter that sends out an invisible beam, and a receiver that reads the reflected signal, and when you hold the phone to your ear, the beam bounces off the surface of your head and returns to the receiver, signaling the system to turn off the display.
This process is almost instantaneous, but software failures or physical obstacles can disrupt the cycle. MIUI, the shell installed on the smartphone, constantly polls the state of the sensor. If the distance to the object is less than a few centimeters, the energy saving mode and protection from false presses are activated.
It’s worth noting that the sensor responds not only to solid objects, but also to dense materials. Cases with high sideways or thick protective glass can create a “dead zone” in which the phone will think that it is constantly in the ear, and extinguish the screen at inappropriate moments.
- 📡 The emitter generates infrared light that is invisible to the human eye.
- 👁️ The receiver records the intensity of the reflected signal.
- ⚙️ The processor analyzes the data and decides to turn off the screen.
Understanding this mechanism helps diagnose problems: if the sensor is contaminated, the signal simply cannot pass through the dirt layer, and the phone stops responding to the approach.
Diagnostics and testing through the engineering menu
Xiaomi has a built-in CIT engineering menu to check the equipment's health, which is the most reliable way to determine whether the sensor is physically working or the problem is in the software, and access to this menu is through a standard dialer.
To get into the diagnostics menu, open the Phone app and type in the combination ##6484##. Once you enter the last digit, the list of tests will open, you will need to find the "Proximity sensor" or "Proximation Sensor" item, which is usually at the top of the list or in the "Common tests" section.
Inside the test, you'll see a numerical value. When your hand is away from the top of the phone, it should be close to 5.0 or 0 (depending on the calibration version), and when you hold your hand to the top right of the screen, the value should change, indicating the sensor response.
☑️ Testing the sensor in CIT
If the test values do not change regardless of hand hand-holding, this may indicate a physical failure or critical failure of drivers, in which case software calibration may not help, and you will need to intervene in the hardware.
Sensor calibration procedure
Oftentimes, the sensor is in good shape, but it's downed, and you need to have a forced calibration. In the same CIT engineering menu, after you pick up the Proximity sensor, you usually have a Calibration button, or you can reset the settings, and you click on it and follow the instructions on the screen that you can ask to cover the top of the phone with your hand and then remove it.
An alternative calibration method is available via the phone's hidden menu. Dial ##7726522632## (corresponding to the letters PCT Calibration) This will open a special window to calibrate the proximity sensor. Press the "Start" button and wait for the process to complete without closing the application.
Once calibrated successfully, the device needs to be restarted, which will reset the sensor's cached data and apply new sensitivity factors, and rebooting is a mandatory step without which the changes may not take effect.
⚠️ Note: Do not calibrate in bright sunlight or under a straight lamp, as external infrared radiation may distort the results of the setting.
If standard codes don’t work on your version of MIUI, you can use third-party apps from Google Play, such as “Proximity Sensor Reset/Fix”, which automate this process through system access rights.
Influence of protective glasses and covers
One of the most common reasons Redmi 8 malfunctions is accessories, and security glass manufacturers often make the black bezel too wide or use a material with insufficient transparency for the IR rays at the top, which physically blocks the sensor from working.
If the phone stopped extinguishing the screen after the new glass was glued, that's the problem 90 percent of the time. Some users solve the problem by carefully cutting a small hole over the sensor, even though it spoils the aesthetics. The more appropriate way is to replace the glass with a model with a cutout under the sensor or a better transparent end.
Magnets can also interfere with work, and silicone ears that go into the front panel can block the sensitivity, so remove the case and check the phone naked to rule out this.
How to check the glass without removing?
The table below shows common accessory problems and their solutions:
| Problem. | Symptoms. | Decision |
|---|---|---|
| Black glass frame | The screen's not going out. | Replacement of glass or cutting of a hole |
| Mud in the net | The screen goes off on its own. | Cleaning of the top with alcohol |
| Thick case | Unstable work | Removal of the cover during calls |
| Cheap glass | Delayed reaction | Installation of a quality accessory |
Software settings and reset
If physical factors are excluded, you should consult the software settings. MIUI has a feature called Approximation Sensor, which can sometimes be disabled or not work properly due to application conflict. Check the settings in the "Applications" -> "Settings" -> "Incoming calls".
Make sure the screen is on/off during a call. It’s also worth checking for system updates. Xiaomi regularly releases patches to fix sensor errors. Go to Settings → About Phone → System Update and check for a new version.
In extreme cases, if nothing works, you can reset all settings to factory settings. This action will delete all user data, so you need to make a backup. Reset often eliminates deep software errors accumulated during the use of the smartphone.
After resetting, the phone will return to its original state and the sensor drivers will be reinstalled again, which often solves the problem of “software sticking”.
Hardware repair and replacement of the module
When software methods and cleaning fail, the sensor module itself or the plume connecting it to the motherboard probably failed. In Redmi 8, the proximity sensor is often soldered on the bottom button plume or integrated into the top of the board, which requires careful disassembly.
Replacement will require a special tool: a suction cup, a set of screwdrivers, a mediator and, preferably, soldering equipment if the component requires soldering. Self-repair without experience can damage the display, which in this model is glued around the perimeter.
The cost of replacing the sensor in a service center is usually low, because the component itself is cheap, but if the plume or power controller is damaged, repairing it may become less cost-effective than buying a used device.
💡
Before contacting the service, be sure to take a screenshot of the test from the engineering menu so that the wizard immediately sees that the sensor does not respond physically.
If the phone is secure, any_attempt_opening will lead to denial of service, so if you have a warranty card, carry the device only to an authorized center.