Do you know these common connector knowledge?

Headphone socket size

This is the 3.5mm stereo headphone jack we bought in the electronics market. Its mechanical dimensions are as follows:
There will be numbers ①②③④⑤ next to the pins on the bottom of the headphone socket, corresponding to the size chart.

Generally speaking, headphones use 3-stage plugs. The diameter of the plug is generally 3.5mm and 2.5mm. Different diameter plugs correspond to different diameter hole headphone sockets, so "male" and "female" should correspond.

According to the wiring of the three-stage headphone plug, the connection of the headphone socket can be determined:

Pin 1 is grounded, pin 2 is connected to the right channel (Right), and pin 5 is connected to the left channel (Left). When the headphone connector is not inserted into the socket, pins 2 and 3, and pins 4 and 5 are connected together, but once the connector is inserted into the socket, pins 2 and 3, and pins 4 and 5 will be separated. So from the perspective of system reliability, pins 3 and 4 should be grounded. In this case, when the earphone is not plugged in, the left and right channel inputs are grounded, and the system input is 0. Many times, we will leave the unused pins 3 and 4 in the air, then the 2 and 5 pins are also left in the air, which brings the risk that if a large current is connected from the outside, it will be transmitted from the 2 and 5 pins. onto the board, which will burn the wafer.

In addition to the three-segment headphone connector, there are also four-segment types. The four-segment type has one more microphone/answer button than the three-segment type. The definition of the national standard (most mobile phones) from beginning to end (the tail is the wired side) is : Left channel, right channel, MIC, ground. It should be noted that the order of the four-stage headphone connector of the iphone is different, from the head (tip) to the end are the left channel, the right channel, the ground, and the MIC.

Mono headphone socket
A mono phone jack can also be used as an input. It should be noted that A is ground, B should be connected to the input terminal, and F should be grounded. When there is no headphone connector connected, the B pin and the F pin are connected together, so as to ensure that the input is grounded and the input signal is 0. When there is a headphone connector connected, the B pin and the F pin are separated, and the F pin and A are connected together.

DC power input socket size

This is the DC power input socket we usually use. The dimensions are as follows:

This DC power socket is a plug with an inner diameter of 2.1mm and an outer diameter of 5.5.

Power supply polarity: inside positive outside negative

It should be noted that the plug is generally positive inside and negative outside, but it is not excluded that a few self-made plugs are reversed, so to be on the safe side, it is best to measure it with a multimeter before use, so as not to burn the chip.

DC Power Outlet Wiring

The 2-pin and 3-pin of the DC power socket are connected together when the plug is not inserted, and when the plug is inserted, the 3-pin and 2-pin are separated. So feet 3 and 1 should be connected to the ground.