由NE555构成的定时器电路简单,但其定时时间较短,通用性不强,本文介绍一种改进型的定时器,只需在原电路增加两只元件,就能使定时时间提高几十倍。改进型定时器原理图见图1.由图可看出,BGl实际上是放大了电容C2的容量,即C′=βC2,所以定时时间为t=1.1βRC。D2对BGl有一定的温度补偿作用。定时器原理较简单,不再赘述。 The timer circuit formed by the NE555 is simple, but its timing time is short, and its versatility is not strong. This article introduces an improved timer, which can increase the timing time by several tens times only by adding two components in the original circuit. Improved timer schematic diagram shown in Figure 1. It can be seen from the figure, BGl is actually an enlarged capacity of the capacitor C2, C ’= βC2, so the timing of t = 1.1βRC. D2 has some temperature compensation for BG1. Timer principle is simple, not repeat them.