The TV remote control does not work. Buttons or equipment don't respond, won't turn on, won't change channels, etc. These are very common scenarios. How to know if there is a problem with the equipment, it is simply the remote that is damaged, the batteries are already exhausted and they must be replaced?
Remote controls based on infrared technology emit light that cannot be seen with the naked eye, because it is not within the range of light visible to the human eye. In other words, it is invisible. However, this light can be detected by a digital camera, such as the camera of any cell phone. In this way it is easy to deduce if the remote control is working well, the battery is in good condition or if in the worst case it is the receiving equipment that has a problem..
How to see infrared light from a remote control
Everything consists of pointing the front of the remote control (which is where the infrared led that sends the signal is normally located) towards the camera of the Android device. Press any button on the controller. If the control and the batteries are in good condition, in the viewfinder of the camera application you will be able to clearly see a purple light each time you press a button.
If the remote control emits a dim light, the batteries are probably discharged and a replacement will be needed very soon, although it is possible that the remote also has a good time of use and the infrared led is noticeable. In some cases it may also be a characteristic of the control or the pre-installed infrared. It can emit low or weak light, even with fresh or fully charged batteries..
If no light appears, the battery (s) may no longer work, or the control has a problem. If it happens only with some buttons, then obviously there is a problem with only those particular buttons. Remember that this trick only works with remote controls that use infrared technology to send the signal. That is, you will not see this violet light in remotes that use Bluetooth technology (such as the control of the Xiaomi Mi Box, Amazon Fire TV Stick and other streaming TV devices or Android TV Box) or Radio Frequency.
This trick does not work if you use an advanced camera or DSLR, as these types of cameras have an infrared filter that helps reduce noise in photos, but also blocks infrared light from the remote control. The same happens with the rear camera of the latest generation iPhone phones from Apple, so in these phones the user must use the front camera..
References : Sony
How to achieve the bokeh effect (unfocused background) with the camera of any cell phone
Google allows you to read QR codes with the cell phone camera
How to translate with CAMERA, by photos or images