who knows about noises?

[E.persia]

hi every body
I have a signal generator thak works with 555
sometimes I see a a noise like digital FM that I think it from 50hz
220 (network voltage)
what i can do to remove it I dont know even when it comes
may be its the malfunction of breadboard
but this my problem the output square wave wavelenght decrease and
increase priodically!
what i can i do for such a thing?

 

[Bob Masta]

On Sat, 11 Oct 2008 03:41:09 -0700 (PDT),
"E.persia" <erfan.talebzadeh@gmail.com> wrote:

hi every body
I have a signal generator thak works with 555
sometimes I see a a noise like digital FM that I think it from 50hz
220 (network voltage)
what i can do to remove it I dont know even when it comes
may be its the malfunction of breadboard
but this my problem the output square wave wavelenght decrease and
increase priodically!
what i can i do for such a thing?

Sounds like you need a power supply with better
regulation!

Best regards,


Bob Masta

DAQARTA v4.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
FREE Signal Generator
Science with your sound card!

 

[Eeyore]

"E.persia" wrote:

hi every body
I have a signal generator thak works with 555
sometimes I see a a noise like digital FM that I think it from 50hz
220 (network voltage)
what i can do to remove it I dont know even when it comes
may be its the malfunction of breadboard
but this my problem the output square wave wavelenght decrease and
increase priodically!
what i can i do for such a thing?

Try explaining the question properly.

Graham

 

[Michael Black]

On Sat, 11 Oct 2008, E.persia wrote:

hi every body
I have a signal generator thak works with 555
sometimes I see a a noise like digital FM that I think it from 50hz
220 (network voltage)
what i can do to remove it I dont know even when it comes
may be its the malfunction of breadboard
but this my problem the output square wave wavelenght decrease and
increase priodically!
what i can i do for such a thing?

Bob Masta said a better power supply, which is a good guess.

There is also the "voltage reference" pin on the 555, which is pin 5.
Varying the voltage there will shift the frequency of the 555 oscillator,
and if it's audio frequency injected there the oscillator will be
frequency modulated. Putting a bypass capacitor on pin 5 will fix
that.

Of course, in order for that to be the problem, there has to
be some strong AC nearby. While many 555 circuits will show that
pin bypassed, I've never bypassed it 35 years of using the IC, and
I've never had a problem.

Michael

 

[John Fields]

On Sat, 11 Oct 2008 03:41:09 -0700 (PDT), "E.persia"
<erfan.talebzadeh@gmail.com> wrote:

hi every body
I have a signal generator thak works with 555
sometimes I see a a noise like digital FM that I think it from 50hz
220 (network voltage)
what i can do to remove it I dont know even when it comes
may be its the malfunction of breadboard
but this my problem the output square wave wavelenght decrease and
increase priodically!
what i can i do for such a thing?

---
Connect a 100ľF aluminum electrolytic and a 470nF ceramic capacitor, in
parallel, from pin 8 to pin 1 on the 555.

Connect the + side of the electrolytic cap to pin 8 and keep the leads
of both as short as possible.

JF