555 Timer Circuits 555定时器电路

555 Timer IC is one of the commonly used IC among students and hobbyists. The 555 Timer got its name based on its internal design which uses three 5 kilo-ohm resistor in series in the internal design of the circuit, thus giving it the name 555 for the three 5 kilo-ohm resistor. The 555 timer is a very versatile and stable circuit and can be used in a number of different configuration, each having a number of different applications which include: Astable, Monostable, Bistable, and Schmitt Triggers.

555定时器集成电路是学生和爱好者们常用的集成电路之一。555定时器是根据其内部设计而得名的，它在电路的内部设计中使用了三个串联的5千欧电阻器，因此命名为555。555定时器是一种非常通用和稳定的电路，可用于多种不同的配置，每种配置都有多种不同的应用，包括：非稳态、单稳态、双稳态和施密特触发器。

Astable: 无稳态:	In astable mode the 555 can operate as an electronic oscillator. Uses include LED and lamp flashers.	在无稳定模式下，555可作为电子振荡器工作。用途包括LED和闪光灯。
Monostable: 单稳态:	In monostable mode the 555 functions as a “one-shot” pulse generator. Applications include timers	在单稳态模式下，555作为“一次性”脉冲发生器工作。应用包括定时器。
Bistable: 双稳态:	In bistable mode the 555 functions as a flip-flop circuit. Uses include bounce-free latched switches.	在双稳态模式下，555用作触发器电路。用途包括无弹跳锁定开关。
Schmitt Trigger: 施密特触发器	As a Schmitt trigger the the 555 operates as an inverter gate which converts a noisy input into a clean digital output.	作为施密特触发器，555作为逆变门工作，将噪声输入转换为干净的数字输出。

Pin Layout 引脚布局

Pin#__	Name_______	Function	作用
1	Ground 地	Pin 1 connects the 555 timer chip to ground (0V).	接地，作为低电平（0V）
2	Trigger 触发	Pin 2 is the trigger pin. When the voltage of this pin drops to 1 / 3 Vcc (or the threshold voltage determined by the control terminal), the output terminal on Pin 3 will turn ON.	当此引脚电压降至1/3V_CC（或由控制端决定的阈值电压）时输出端给出高电平。
3	Output 输出	Pin 3 is the output pin. The 555 timer’s output is digital in nature. It is either high (+ VCC) or low (0V). The output pin is where you would connect the load that you want the 555 timer to power.	输出高电平（+VCC）或低电平。
4	Reset 复位	Pin 4 is the reset pin. This pin can be used to restart the 555 timer’s operation. This is an active low input, just like the trigger input. If it is momentarily grounded, the 555 timer’s operation will be interrupted and won’t start again until it’s triggered again via pin 2.	当此引脚接高电平时定时器工作，当此引脚接地时芯片复位，输出低电平。
5	Control 控制	Pin 5 is usually connected to the ground line through a small 0.01 µF capacitor. This capacitor serves to level out any fluctuations in the power supply voltage that might affect the operation of the timer.	控制芯片的阈值电压。（当此管脚接空时默认两阈值电压为1/3V_CC与2/3V_CC）
6	Threshold 阈值	Pin 6 is the threshold pin. The purpose of this pin is to monitor the voltage across the capacitor that’s discharged by pin 7. When this voltage reaches 2/3 of the supply voltage (Vcc), the timing cycle ends, and the output on pin 3 goes low.	当此引脚电压升至2/3V_CC（或由控制端决定的阈值电压）时输出端给出低电平。
7	Discharge 放电	Pin 7 is the discharge pin. This pin is used to discharge an external capacitor that works in conjunction with a resistor to control the timing interval. In most circuits, pin 7 is connected to the supply voltage through a resistor and to ground through a capacitor.	内接OC门，用于给电容放电。
8	Vcc 供电	Pin 8 is connected to the DC power supply voltage.The voltage must be at least 4.5V and no greater than 15V. It’s common to run 555 timer circuits using 4 AA or AAA batteries for 6V or a single 9V battery.	提供高电平并给芯片供电。

Formulas 公式

There are a number of equations that can be used to make calculations related to the effective use of the 555 timer within a circuit. These formulas are listed below:

有许多方程式可用于计算电路中555定时器的有效使用。以下列出了这些公式：

Parameter	Formula	Unit
T1 (Time High)	0.693 x (R1 + R2) X C1	Seconds (s)
T2 (Time Low )	0.693 x R2 x C1	Seconds (s)
T (Timer Period)	0.693 x (R1 + 2 x R2) x C1	Seconds (s)
F (Frequency)	1.44 / (R1 + 2 x R2) x C1	Hetz (Hz)
DC (Duty Cycle )	(T1 / T) x 100%	Percentage (%)