Today, we will disassemble a tire pressure monitoring sensor.
What we see here is actually a tire pressure sensor+a wireless transmitter. It also has a receiver with a solar panel, placed inside the car to receive data from the four tire pressure sensors and display it on the screen. The text on the four sensors indicates the front, rear, left, and right wheels, and they should be installed according to the labels on the corresponding wheels.
Cars that were purchased earlier may not have built-in tire pressure sensors, so external ones need to be bought. Of course, if you go to a car repair shop to install tire pressure sensors, they may recommend you install built-in ones, which require removing the tire and inserting the sensor from the inside onto the valve core. This external sensor from a fan has normal detection and transmission functions, but there is a leak between the copper internal thread and the red sealing ring shown in the image above. Therefore, it cannot be used and was sent to me for disassembly.
The diameter of this tire pressure sensor is21.1mm.
The thickness is17.3mm.
By twisting it hard, we can remove the cap, and we can see that there is a button battery compartment inside, with a blackOring sealing the thread. The brother selling the sensor mentioned at the beginning of the article may have never opened it to take a look.
The positive terminal of the battery compartment is a small round SMT patch mounted on the circuit board. It is insulated with a paper made from Qingke barley.
Remove the Qingke paper.
We can see three screws on the circuit board.
After removing the screws, we can take off the circuit board. There is a black circular rubber pad on the circuit board with air holes.
After removing this rubber pad, we find an electronic component soldered onto the circuit board, similar to the barometer used in our flight controllers, with air holes on the casing.
The diameter of the circuit board is17.5mm.
There is a26MHz crystal oscillator on the board. Seeing this oscillation frequency crystal, I roughly understand that the wireless communication method of this sensor might be315MHz. After checking the information, the current working frequency standard for tire pressure sensors in the United States is433MHz, and the European standard is433MHz.
The black chip in the middle seems to encapsulate the pressure sensor, processing unit, and wireless chip together. I couldn’t find the corresponding model based on this silk screen.
Using a flashlight, the red line in the image above shows the routing after the battery negative plate comes in.
There is an inductor at this position.
This looks like an antenna matching circuit, so the final antenna is this screw hole, and when the screw is added, it becomes an antenna? Forget it, I won’t analyze it further. For such a product with strange operations, I can’t understand how it was designed. Anyway, a wireless communication distance of two to three meters is sufficient, right?
In the image above, you can see a Murata high-frequency multilayer inductor.
This concludes the disassembly process of the360 tire pressure sensor. Thank you all for reading.