Difference between Astable and Monostable.

[Sarfaraz]

What is Difference between Astable and Monostable?

 

[KeepItSimpleStupid]

Other synonyms: Free-running and one-shot
Oscillator and Pulse

Astable means two stable states - e.g an oscillator
Monostable - Tends to stable in one state, rest. The circuit generates a pulse. Triggering is edge or level, usually edge.

 

[crutschow]

Astable is free-running.

Monostable requires some form of trigger.

 

[JimB]

Astable means two stable states - e.g an oscillator

I think that you are a bit mixed up there KISS...

BISTABLE means two stable states. The circuit wil remain in one of two stable states until triggered. I will than change to the other state.

ASTABLE means no stable states. The circuit continually oscillates between two states.

JimB

 

[Sarfaraz]

so what is purpose of monostable and astable?

 

[JimB]

As has already been said:

Astable - used as an oscillator

Monostable - used as a Pulse Generator to generate a pulse of defined duration in response to a trigger pulse of unknown duration.

JimB

 

[Sarfaraz]

Thanks for the quick replies,

how long of duration can b set to trigger the pulse? and through which components? I mean, which capacitor and resistor values can be used to set the trigger pulse of duration.
Sorry to bad english.

 

[crutschow]

It all depends upon the type of monostable circuit. For the common 555 timer the output pulse duration, when triggered, is approximately equal to the RC time-constant of the timing components.

 

[KeepItSimpleStupid]

In a lot of cases, on the order of seconds is the max. Issues like leakage currents start to come into play with high value of electrolytic capacitances.

There is a one-shot that uses a counter which can extend the timing interval.

 

[Sarfaraz]

Difference between Astable and Monostable.
ok so how to calculate the RC time?

 

[Sarfaraz]

It all depends upon the type of monostable circuit. For the common 555 timer the output pulse duration, when triggered, is approximately equal to the RC time-constant of the timing components.

ok so how to calculate the RC time?

 

[cowboybob]

1.1 times R times C yields time constant (TC) in seconds. R is in ohms and C is in uF.

E.G., 1Mohm resister and a 1uF cap: 1,000,000 X 0.000001 X 1.1 = 1.1 second TC.

Given that there is always some slop in the stated values of most R and C components, your actual TC will vary slightly.

 

[atferrari]

ok so how to calculate the RC time?

Have you consider using Google for all this?

Basics? is better you deal with them yourself. When you have specific questions on something you cannot solve by yourself, then come and ask here.

Up to here, you could learn easily all that not even posting a single question here. A so wide subject could take millions of questions to be learnt and the hell of TIME.

If you know how to post, you know how to Google. Simple as that.

 

[KeepItSimpleStupid]

ok, so how to calculate the RC time?

Read the datasheet for the part selected. i.e.

Spoiler: Click for answer

RTFM. Read the ... Manual

 

[Sarfaraz]

1.1 times R times C yields time constant (TC) in seconds. R is in ohms and C is in uF.

E.G., 1Mohm resister and a 1uF cap: 1,000,000 X 0.000001 X 1.1 = 1.1 second TC.

Given that there is always some slop in the stated values of most R and C components, your actual TC will vary slightly.

well explain cowboybob , actually i am calculating 1 uF as 1. but now i know that 1 uF is equal to 0.000001. thanx all.

 

[KeepItSimpleStupid]

RC happens to known as the time constant, Yep, uf is 1e-6; mf is 1e-3 ; pf is 1e-9; so 100 uF = 100E-3 etc.

There are some important relationships with the Time constant. One being that at 5 * RC, a capacitor is like 98-99% charged.
See: https://en.wikipedia.org/wiki/Time_constant

Each IC has a different formula. Generally you have to careful and use units of Farads, Amps, Ohms and Seconds,