555 timer astable multivibrator

[electroboy]

In the following astable multivibrator circuit,



in some books, it is mentioned that the duty cycle id

d=( R1+R2)/(R1+2*R2)

in some other books, it is mentioned

d= R2/(R1+2*R2)

which is correct? which one should i use if i want to design a circuit of particular duty cycle ?

please tell me whether duty cycle is Ton/(Ton+Toff) or Toff/(Ton+Toff)

 

[ckshivaram]

see this


https://www.edaboard.com/threads/81131/

 

[srizbf]

duty cycle is Ton/(Ton+Toff)

 

[electroboy]

see this


https://www.edaboard.com/threads/81131/

i can't understand still sir.. please explain me ..

 

[alexan_e]

This page has the equations and a calculator

**broken link removed**

Also check 555 and 556 Timer Circuits

Alex

 

[FvM]

which is correct? which one should i use if i want to design a circuit of particular duty cycle ?
please tell me whether duty cycle is Ton/(Ton+Toff) or Toff/(Ton+Toff)

I think, it's your choice. That's also the reason, why both expressions for d exist.

In my opinion, you would define high output as "on" and duty cycle as Ton/(Ton+Toff).
In this case, the first expression applies: d=( R1+R2)/(R1+2*R2)

 

[alexan_e]

please tell me whether duty cycle is Ton/(Ton+Toff) or Toff/(Ton+Toff)

Normally when we say that the duty cycle is 10% we mean then the output is on for 10% of the period time so I think you should use Ton/(Ton+Toff)

Alex

 

[hareesh_mohan]

Ton/Ton+Toff

 

[sherazi]

duty cycle is ton/(ton+toff)

http://teeblog.blog.com/archives/66/#as Read this for calculations and basic theory

 

[engr.fawad]

you can also try this link for understanding 555 ic as a-stable multivibrator