Reset timing circuit when power is turned on

(1) Introduction to the circuit principle The circuit is shown in Figure 3-41. The function of the ④ pin of NE555 is to operate the circuit when connected to a high level, and to reset the circuit when connected to a low level
. The circuit is connected to the ruler at pin ④. and G have a time constant function. Therefore, after the power is turned on, the ④ pin will not rise to +ULI immediately. ,
it needs to rise to +Ud- after the delay of the wind and Cz time constants. During this period, even if pin ② inputs a trigger pulse. ③Pin output still remains low
. The island and pin are the limiting resistors of NE555, which are used to prevent excessive current in c2. The FTL level trigger pulse directly triggers
the ② pin of NE555 through Rz . VD1 is used to quickly discharge C2 when the power supply is disconnected, and the output pulse width is T=Rs.
(2) Component parameter selection The selection of components is shown in Figure 3-41, and there are no special requirements.
(3) The reset timing circuit when the power is turned on is shown in Figure 3-41.