Headphones and piezoceramic buzzers
Headphones and piezoceramic buzzers
Headset is also an electro-acoustic conversion device,which is similar in structure to an electric speaker,it is also composed of magnet,voice coil,vibrating diaphragm, etc,but the voice coil of the earphone is mostly fixed.
The main technical parameters of the earphone are frequency response,impedance, sensitivity,harmonic distortion and so on.with the continuous development of audio technology,the development of headphones is also very rapid.Modern audio equipment,such as high-level walkman,high quality stereo, etc,are widely used in flat film moving-coil earphones,the structure is more similar to the loudspeaker, and has the advantages of good frequency response,small distortion,etc.The flat film moving-coil earphones are mostly low-impedance type,such as 202X2,302X2 and so on.
The multimeter can be used to detect the on-off condition of the earphone conveniently. For the two-channel earphone,there are three leading-out terminals on the plug,and the contact end of the final end of the plug is a common end,and the front end and the middle contact end are respectively left,right channel extraction end. When testing,the multimeter is placed in the " RX1 " block,and any stylus is connected to the public end of the earphone plug, and then another pen is used to touch the other part of the earphone plug two leads,the corresponding left or right channel headphones should be issued " click " sound,the pointer should be deflected,the left and right channel headphone resistance should be symmetrical.If the headset is silent in the measurement, the multimeter pointer is not deflected,indicating that the corresponding headphones are broken or the internal solder joints are disconnected.If the pointer is placed near the zero position,it is indicated that there is a short circuit between the inner lead of the earphone or the plug of the earphone.If the pointer indicates the normal resistance, but the sound is very light,usually the gap between the headphone diaphragm and the magnet is not appropriate.
Piezoelectric Ceramic Buzzer
Piezoelectric ceramic horn
Piezoceramic horn is a flexural vibrating piece that is pasted with piezoelectric ceramic sheet and metal sheet.
Under the excitation of the shock circuit,the alternating electric signal causes the piezoelectric ceramic to drive the metal sheet to produce a bending vibration,and a clear sound is given along with it.Compared with the general loudspeaker,it has the characteristics of small volume,light weight,thin thickness,low power consumption,good reliability,low cost,and sound response to 120dB.It is widely used in electronic watches,pocket calculators,toys,doorbell,mobile telephone and all kinds of alarm facilities.The piezoelectric ceramic chip is written in letter B,and its diameter is 15mm, 20mm,27mm,35mm and so on,and the thickness is only 0. 4~0.5mm.The common models are HTD20, HTD35,etc.Compared with the ordinary loudspeaker,the piezoelectric ceramic horn with feedback electrode is divided into two parts,the main electrode and the feedback electrode,the positive feedback signal is removed directly from the feedback electrode,which makes the concussion circuit very simple.The model of piezoelectric ceramic loudspeaker with feedback electrode includes FT-27-4BT,FT-3529BT and so on.
Piezoelectric ceramic buzzer is made of a multivibrator and a piezoelectric ceramic plate, and the external plastic shell is used for packaging, it's a piezoelectric ceramic buzzer. The multivibrator is generally composed of an integrated circuit.After switching on the power,the multivibrator vibrates and outputs the audio signal ( generally 1.5 ~ 2.5 kHz ),driving Piezoelectric Ceramic Pieces with Impedance Matching Device.The working voltage of the domestic piezoelectric buzzer is generally DC 3 ~ 15V,and there are two leading-out lines of positive and negative.A block diagram of the piezoelectric ceramic buzzer is shown in Figure.
Detection of piezoelectric ceramic buzzer.
The detection of the piezoelectric ceramic buzzer will dial the multimeter to the DC 2.5V block,and put the piezoelectric buzzer on the wooden table,side up with a piezoelectric ceramic piece.Then,a pen of the multimeter is contacted with the metal sheet of the buzzer,and the other pen is lightly touched on the ceramic piece of the piezoelectric buzzer,it can be observed that the pointer of the multimeter fluctuates with the touch of the pen,and the bigger the swing amplitude is,the higher the sensitivity of the piezoelectric ceramic buzzer is;if the multimeter pointer does not move,it shows that the measured piezoelectric ceramic buzzer has been damaged.