how to distinguish between public common yin and public common yang:

First of all, we find a power supply (3 to 5 volts) and a 1K (several hundred ohms) resistor. VCC is connected in series with a resistor and GND is connected to any two feet. There are many combinations, but there is always one LED that will emit light. It is enough to find one, then GND does not move, and VCC (string resistor) touches the remaining feet one by one, if there are more than one LED (usually 8), then it is common. On the contrary, use VCC and GND to touch the remaining feet one by one. If there are multiple LEDs (usually 8), then it is common.

You can also use a digital multimeter directly. The red stylus is the positive pole of the power supply and the black stylus is the negative pole of the power supply.