The Honor wired earphones that were given away when I bought the product in the past are a bit antique when I pick them up and look at them. They will only tie knots and eat ashes.
1. Product appearance
Honor semi-in-ear wired earphones, with L/R silkscreen logo on the left and right earphones, and metal dust-proof mesh for the sound outlet. The wire control button is on the side of the R right earphone after the line is split. It includes 3 touch buttons, which correspond to: volume +, microphone transmission, and volume - from top to bottom. There is a small hole under the silk screen of the honor logo on the back for Microphone pickup hole. The earphone interface adopts a 3.5mm cylindrical plug, and there are 4 contact terminals on the cylindrical plug. Smartphones now basically cancel the matching headphone jack, and need to use an adapter cable to switch to type C to connect to the phone.
2. Product dismantling analysis
3.5mm audio interface
There are generally two types of audio interface for wired earphones, three-segment and four-segment, the difference is whether there is a microphone to send calls. Three wires serve as control wires for the three devices.
Cut from the audio interface to the splitting position of the left and right earphone harnesses, there are actually 6 wires inside, of which three copper-colored ground wires are respectively connected to the GND of the left and right earphones and the microphone. The actual inner copper wire is very thin, covered with a lot of braided fibers.
Wire control button The
wire control button module on the right earphone harness is disassembled as follows. The three buttons for volume control and microphone control are arranged sequentially on the PCBA. The structural contacts on the upper cover and the button domes feel better. Open the PCBA and you can see the circuit and components on the board. The four wire harnesses are separated here, two wires are connected to the control board, and the other two wires are connected to the right earphone speaker. There is a cylindrical microphone on the wire control board, and there are corresponding positioning slots and sound pickup openings on the bottom shell.
Use a multimeter to conduct simple wiring measurements to get the volume control circuit on the wire control board as follows. When any button is pressed and closed, the positive and negative poles form a loop, and the impedance quotes of the circuit at this time are passed to the opposite end (mobile phone). It is speculated that the positive pole here is not a constant voltage power supply, and there is a pull-up resistor on the opposite end, so as to achieve different levels of different levels by sampling the positive pole of the microphone when different switches are closed.
After the middle button is pressed, the microphone is connected to the loop, and the frequency amplitude of the sound wave received by the microphone will change the impedance change in the microphone, corresponding to the level signal of the change in the microphone control line sampling to the sound wave conversion.
Earphone speaker
Disassemble the speaker shell as follows, the signal wire is soldered to the inner speaker of the earphone with relatively full solder joints, and the other end is reinforced with red glue and routed to the inner speaker cavity. The wire harness is knotted inside the earphone to prevent the solder joints from falling off and being damaged due to external pulling.
Open the speaker cavity as shown in the figure below. The positive electrode of the earphone passes through the position of red glue to the bottom to form a red coil. Under the coil is the fiber diaphragm. ), which is just in the middle of the red coil below when assembled.
The work here uses the principle of electromagnetic induction. The red coil is in the magnetic field formed by the central magnet. When the speaker is working, the changing current passes through the coil. The coil is affected by the magnetic field force to drive the lower fiber membrane to vibrate together, and the vibration of the fiber diaphragm generates sound waves that are transmitted to the ear. .
3. Production test analysis
PCBA test: The headphone PCBA has only one wire control board, and two TP points are left on the board to lead out the positive and negative poles (on the side of the button). FCT production test speculation: pin power supply and voltage sampling at the two test points of the PCBA, pneumatic The device then presses 3 buttons in turn to sample the level change at this time (simulation works normally)
The finished product test of the whole machine: the audio interface is connected to the accompanying test equipment (providing audio playback and microphone reception), and the end of the earphone speaker is placed in front of the audio receiving equipment to test the audio analysis quality.
Ps: In actual production, only a simple sampling test may be done.