DIY_MPU

Demonstration video of MPU accelerometer design based on PCB spiral architecture copper-clad capacitance detection technology
: https://www.bilibili.com/video/BV15r421u72u/
Principle introduction: When a soft object is subjected to sufficient acceleration, it will produce slight deformation, resulting in a displacement of a very small gap. Since capacitance is related to the area, distance, and dielectric of the electrode plate, a change in capacitance will occur when the dielectric and area remain constant. By detecting the capacitance, the degree of deformation of the object can be obtained, and thus the acceleration can be measured.
Therefore, it is necessary to first design an object that is easily deformable. PCB is an excellent material (it's readily available). However, FR-4 is relatively rigid. We know that steel bars are very hard, but a 10-meter-long steel bar is easily deformed. Therefore, it is necessary to find a way to extend the length of the PCB. However, if it exceeds 10cm, it cannot be used without a solution, so a more comprehensive approach is needed.
Ultimately, the PCB length was extended using a spiral slotting method, allowing the lengths of multiple consecutive sides to be superimposed to support the moving parts.
This board was then mounted very close to another copper-clad board (using only a thin spacer). When the board is subjected to acceleration, it deforms, causing a change in capacitance. To detect this capacitance change, an oscillation circuit was designed. In this circuit, the period of the oscillation changes as C47 changes, resulting in a PWM waveform that is affected by the capacitance value. The output is then connected to the PA9 pin of the microcontroller to detect the PWM period.
This circuit series was then drawn on another copper-clad board, and
the two boards were finally mounted together. After writing the program, acceleration detection was achieved. Due to factors such as PCB material and microcontroller timer resolution, the final resolution was only 1.96 meters per second squared. The resolution could be further improved by replacing the PCB with a thinner one and using a microcontroller with a higher clock speed.