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[SOLVED] Square wave generation with 555 timer IC

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moonnightingale

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Hi

I am having a 600 Hz signal,
I want to generate Square wave by using 555 Timer IC and duty cycle to be 70 %
How to go abt it

Thanks
 

moonnightingale

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moonnightingale

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I am sorry,
In my Previous post, i dint understood your problem properly. To convert signal to square wave, you should design schmitt trigger. You may use either Opamp or 555 timer.

Non-Inverting Schmitt Trigger Calculator
The Schmitt Trigger - Electronic Theory

Thanks Vinoth for ur reply,
Actually i have to convert sinusoidal signal of 600 Hz to Square wave having duty cycle of 70% by using 555 Timer IC.

Can u send me link of website which can explain this to me. U can also see the attached Pic to understand my requirement, it is just a block diagram

thanks a lot
 

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  • 555 IC Requirement.bmp
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barry

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If your input is a fixed 600 Hz, then you can run your sinusoid into a comparator/schmitt trigger (to get a squarewave) and then configure your 555 as a monostable with a pulsewidth of 833uS. You'll have to differentiate your squarewave to get the narrow pulses required to trigger the 555.
 

moonnightingale

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thanks berry,
so u want to say that

1. First i convert sine wave to Square Wave through Comparator/Schmitt Trigger

2. Then 555 Timer IC should be used to get the desired duty cycle of that square wave

How did u calculate pulse width of 833 usec.
Kindly explain me as i have to give input of 16 sine wave through switch,

Is there any method by which 555 timer alone can convert Sine wave to Square wave with desired duty cycle
 

barry

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There's no way (to my knowledge) that a 555 can convert a sine to square. What is the amplitude of your sine wave?

The 833 uSec is wrong; it should be 1.1667mS. (1/600Hz * 70%). I gave the answer for 50% DC.

If you are trying to do this for different input frequencies, it won't work, as it will give you a 1.1667 mS pulse regardless of the input frequency.
**********************
But wait a minute! I take back almost everything I said. I just realized: The 555 has 2 comparators built in. There must be some way you can use those comparators to look at the sinewave input and toggle the internal flip-flop appropriately. I don't have time to look at that now, but I think that's your answer. Look at the data sheet and application notes for the 555; this is not the 'normal' way of using the part, but I think it should work.

Let us know what you find.
 

jpanhalt

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This sounds like a homework assignment, and I suspect the question is designed to let you use the trigger pin for the monostable configuration. Note, the NE555 triggers on a negative pulse to less than 1/3 VCC.

Source:NE555 Datasheet: https://www.nxp.com/documents/data_sheet/NE_SA_SE555_C_2.pdf

Due to the nature of the trigger circuitry, the timer will trigger on the negative going edge of the input pulse. For the device to time out properly, it is necessary that the trigger voltage level be returned to some voltage greater than one third of the supply before the time out period. This can be achieved by making either the trigger pulse sufficiently short or by AC coupling into the trigger. By AC coupling the trigger, see Figure 6, a short negative going pulse is achieved when the trigger signal goes to ground. AC coupling is most frequently used in conjunction with a switch or a signal that goes to ground which initiates the timing cycle. Should the trigger be held low, without AC coupling, for a longer duration than the timing cycle the output will remain in a high state for the duration of the low trigger signal, without regard to the threshold comparator state.

I believe a 70% duty cycle (i.e. a single pulse of 70% of the sine wave period) was chosen to allow the input to return to >1/3 Vcc before the end of the pulse. (My math is a bit rusty.)

John
 

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