nikhalidnitypo

modified 11 years ago

555 Astable.. Those who can help see discription.

117

02:31:38

I want to get perfect 50% duty cycle. But i dont know what is going wrong.........
Plz help..... !!!!

published 11 years ago

hurz

11 years ago

Without agly tricks 555 is not able to make a perfect 50% duty cycle.

acm45

11 years ago

You need 2 diodes and another resistor

qwerfgh

11 years ago

Where should i connect them ?? @acm45..

qwerfgh

11 years ago

Hmm... I can get close to 50% by making R2 >> R1 .. But thats not perfect... Any other ugly trick ??? @hurzzz

rockwog

11 years ago

I solved your problem bud ...I've got the solution ...look for astable 555 at 50 percent

rockwog

11 years ago

Yo just needed 1 more resistor..I hope these guys aren't engineers

qwerfgh

11 years ago

Hmmm.... Thankss bro see my cmnt on ur circuit.... :)

hurz

11 years ago

@qwerfgh, yes the agly ones are with diodes and a pot which has to be finetuned. But 555 itself is not able to do a perfect 50% cycle, as you know only close to by R2>>R1

qwerfgh

11 years ago

Hmmm . thanks for your comments guyzzz ....

hurz

11 years ago

In this configuration were you don't use the discharge pin you have to improve the rail2rail performace somehow. One agly hack is to put two inverter at 555 output. This makes it somehow railtorail, but makes 555 itself useless. Using two additional inverter is waste of material, because those inverter itself could be used as 50% duty cycle oscillator.

mikey5869

11 years ago

Hurl how about using the circuit above but hold the control pin at around 5.5v thats almost exactly 50% mark/space, plus if you use a "pot" of around 1K to vary the voltage to the control pin it is then variable so fine adjustments can be made. Plus it will also stay reasonable accurate if the supply voltage changes.

mikey5869

11 years ago

*hurz

hurz

11 years ago

All solutions with pot are not perfect. They are only close to 50%

hurz

11 years ago

Perfect would be, e.g. double 555 freq and use a FF two divide it to a "perfect" 50% duty cycle

rockwog

11 years ago

I got it bro. Put an inductor in line between your cap and resistor to slow the return of the time constant of the cap

safwat

11 years ago

You must connect dis with register a

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