555定时器非稳态(或自由运行)多谐振荡器原理图及电路分析

ID:161768 · 发表于 2017-4-17 16:23

电容 C 通过 R1 和 R2 充电，当电压上升到 2/3 的电源电压时，六脚检测到此状态，并且 7 脚连到地。电容通过 R2 放电，直到它的电压小于
1/3 的电源电压，并且 2 脚检测到该状态，关闭七脚，重复以上的循环。上面的电阻是为了防止 7 脚被损坏，因为当六脚检测到 2/3 的电源电压时它短接到 0V。它的阻值相对于 R2 来说很小，并且不会干扰到振荡周期的计算。

下图适用于非稳态电路：

Using the graph:（计算部分，不敢随便翻译）
Suppose R1 = 1k, R2 = 10k and C = 0.1u (100n).
Using the formula on the graph, the total resistance = 1 + 10 + 10 = 21k
The scales on the graph are logarithmic so that 21k is approximately near the "1" on the 10k. Draw a line parallel to the lines on the graph and where it crosses the 0.1u line, is the answer. The result is approx 900Hz.
Suppose R1 = 10k, R2 = 100k and C = 1u
Using the formula on the graph, the total resistance = 10 + 100 + 100 = 210k The scales on the graph are logarithmic so that 210k is approximately near the first "0" on the 100k. Draw a line parallel to the lines on the graph and where it crosses the 1u line, is the answer. The result is approx 9Hz.
The frequency of an astable circuit can also be worked out from the following formula:

文章摘自：50个555定时器电路分享(一个国外优秀文档的翻译，个人觉得是对于掌握555定时器电路最有帮助的资料)每个电路都有详细的解说，全部内容请下载:http://www.51hei.com/bbs/dpj-80748-1.html
作者:MCU起航

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555定时器非稳态(或自由运行)多谐振荡器 原理图及电路分析

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555定时器非稳态(或自由运行)多谐振荡器原理图及电路分析