某控制系统的方框图如图1所示。其计数脉冲来自PC机的输出。它的输出信号如图2所示,实际上,常因PC机输出继电器触点的抖动而产生过渡干扰脉冲(如图2b),进而引起计数器误跳。为了消除这种现象,可用555单稳电路对脉冲信号进行整形。电路工作原理图如图3。PC机来的脉冲送到555单稳电路的脚②,该脉冲的下跳沿使555电路翻转,输出脚③变成高 A control system block diagram shown in Figure 1. The count pulse comes from the PC’s output. Its output signal shown in Figure 2, in fact, often due to PC output relay contact jitter generated transitional interference pulse (Figure 2b), and then cause the counter to jump. In order to eliminate this phenomenon, the pulse signal can be shaped with 555 monostable circuit. Circuit schematic shown in Figure 3. PC to the pulse 555 monostable circuit to the foot ②, the pulse of the next hop 555 circuit flip, the output pin ③ becomes high