Tire leak detector circuit

(1) Analysis of circuit composition and working principle. The circuit of the tire
air leakage detector is composed of microphone BM, preamplifier
, tone control, volume control and power amplifier
. As shown in the figure, the preamplifier circuit is composed of
transistor VTI. , VT2 and capacitor c], C, resistor
Ri, fun composition. RP is the volume potentiometer. The selector switch
S and the capacitor C-Lu C6 form a tone control circuit. The power
amplifier circuit is composed of an integrated circuit E1 and a capacitor C3, G.   The microphone BM is installed on the probe of the stethoscope and is used to detect tire leakage, convert the sound signal into an electrical signal, and then couple to the base of VT1 through Cl, and then preamplify the volume and tone through VT1 and VT2 After control, input from the ③ pin of the power amplifier integrated circuit IC. The audio signal amplified by the IC is output from its ⑤ pin, coupled to the headphone socket xs via G, and finally the amplified sound is restored through external headphones.     (2) Component selection R. Choose 1/4W metal film resistor; Rz choose 1/2W metal film resistor.     C,, c2, C4~G and G use monolithic capacitors or polyester capacitors; G, C and Ca all use aluminum electrolytic capacitors with a withstand voltage of 16V.     VT1 and VT2 use S9013 transistors. LC selects the LM386 power amplifier integrated circuit . BM uses high-sensitivity electret microphones or piezoelectric ceramic sheets.