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A help in Liquid Level Alarm Project about IC 555

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K2DGR8

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Dear All,

Below is the circuit diagram of my project.
Liquid level Alarm.gif
Project is in the working state, but just had a query related to it.

Why IC 555 has been used here at the input of Buzzer?
Why cant we connect output of Transistor 2 directly to Buzzer?

Thank you in advance.
 

The first 555 is a slow oscillator, the second one is a fast oscillator. The second one produces the tone in the buzzer (loudspeaker) and the first one makes it go on and off slowly. If you miss out the first 555 it will give a contuinuous tone instead of going on and off repeatedly.

Brian.
 
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    K2DGR8

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The first 555 is a slow oscillator, the second one is a fast oscillator. The second one produces the tone in the buzzer (loudspeaker) and the first one makes it go on and off slowly. If you miss out the first 555 it will give a contuinuous tone instead of going on and off repeatedly.

Brian.

Thanx a lot Brian! But, the Buzzer I have already produces sound in beeps(I connected across a DC battery), i.e., it doesnt produce a continuous sound.. So, I think, there is no need of first Timer IC..
Now, what does second timer IC exactly do to produce a sound? I know the working of Timer IC, but cant understand why buzzer needs pulses, if it can be operated on DC(i.e. signal from collector of Second Transistor)?
 

cant understand why buzzer needs pulses, if it can be operated on DC
The circuit diagram in post 1 shows a loudspeaker, not a buzzer. A loudspeaker does not work on DC, so it needs the 555 oscillator.

If you use a buzzer, you don't need the second 555. You still need the first one because the output from TR2 is not strong enough for the buzzer.
 
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    K2DGR8

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The circuit diagram in post 1 shows a loudspeaker, not a buzzer. A loudspeaker does not work on DC, so it needs the 555 oscillator.

If you use a buzzer, you don't need the second 555. You still need the first one because the output from TR2 is not strong enough for the buzzer.

K... Gotcha!! Thanx a Lot!!:grin:
 

you can remove both ic . and connect a buzzer there ..
But the buzzer will ON whenever a pulse from transistor .
 
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    K2DGR8

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Ok... I'll do it! Thank you!

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Ok... I'll do it! Thank you!
 

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