As shown, it is a high-stability pulse period that gradually broadens the timing circuit. In the circuit, NE555(1) constitutes a pulse gradually widening timing circuit, NE555(2) constitutes a monostable trigger circuit, and NE555(1) and NE555(2) are connected by diode VD1. When the switch S1 is not pressed, the internal transistor of the NE555(2) is turned on, the 3 pin outputs a low level, and the diode VD1 is turned on to make the voltage on the capacitor C1 zero, and the NE555(1) timer cannot operate.
When the switch S1 is pressed, the switch S1 will generate jitter for a period of time, causing Ucc to intermittently charge C1, causing the output waveform of the NE555(l) to be unstable. However, due to the existence of NE555(2), during this time, the output of pin 3 of NE555(2) is low, and the voltage on capacitor C1 is zero through diode VD1, so NE555(1) can't work, so avoid Rabbit has the effect of jitter on S1.
When the switch S1 is reset, the negative pulse generated by the R4 and C4 differentiating circuits triggers NE555(2) to make the output change from low level to high level. At this time, VD1 is turned off, C3 is charged to C1, NE555(1) starts to oscillate, and a period in which the output negative pulse width is constant becomes a gradually broadened pulse train. This process continues until the voltage on C2 reaches (2/3) Ucc, the trigger of NE555(2) is reset, or C1 has not been able to charge to (2/3) Ucc before then.
The mechanical Buzzer uses a magnet to move a reed up and down quickly to emit a lower-pitch buzz! It's quieter than the piezoelectric buzzer but uses more power, so you the terminals will have to be closer to the battery packs. To use them, you'll need to match the wire colors to the wires from the battery pack.
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