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Forum index » Electronix » Basics
square waveform (555)
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Sun Jul 16, 2006 1:49 pm    Post subject: square waveform (555) Reply with quote
Hello everyone,

Just liek to know if it is a normal thing that at LOW frequencies ( 15-25
Hz) that the output of a 555 timer is not exactly a square wave. At higher
frequencies I get a perfect square wave (say between 50 and 300Hz). But at
lower frequencies, the voltage when get to high, slowly decreases until the
output of the 555 turns off.
So usinf a 6v supply, instead of getting 6v high 0v low. I get 6v high,
5.99v, 5.98 ... 5.89, (there is a small slope at the high) then it goes
low to 0v. I am using 50% duty cycle.

I hope I was clear enough
thank you,

ken
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Tim Williams
electronics forum Guru


Joined: 18 May 2005
Posts: 668

PostPosted: Sun Jul 16, 2006 3:19 pm    Post subject: Re: square waveform (555) Reply with quote
"Ken O" <lera@yahoo.com> wrote in message news:e9dg5e$nv8$1@nntp.aioe.org...
Quote:
So usinf a 6v supply, instead of getting 6v high 0v low. I get 6v high,
5.99v, 5.98 ... 5.89, (there is a small slope at the high)

5.89V counts as damned close to 6V if you ask me. You're lucky to get that
much with silicon, a 0.6V drop is more typical (and you'll find it under a
stiffer load).

I don't know why it would drop. It could be real, some effect internal to
the 555, a power supply issue (is +V varying by 0.1V as well?), or something
with your meter, or how you're measuring it.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Sun Jul 16, 2006 4:47 pm    Post subject: Re: square waveform (555) Reply with quote
"Tim Williams" <tmoranwms@charter.net> wrote in message
news:JOsug.3162$0r6.1663@fe05.lga...
Quote:
"Ken O" <lera@yahoo.com> wrote in message
news:e9dg5e$nv8$1@nntp.aioe.org...
So usinf a 6v supply, instead of getting 6v high 0v low. I get 6v high,
5.99v, 5.98 ... 5.89, (there is a small slope at the high)

5.89V counts as damned close to 6V if you ask me. You're lucky to get
that much with silicon, a 0.6V drop is more typical (and you'll find it
under a stiffer load).

I don't know why it would drop. It could be real, some effect internal to
the 555, a power supply issue (is +V varying by 0.1V as well?), or
something with your meter, or how you're measuring it.


Ok I put up a web page to show what I get on the scope:
http://www3.sympatico.ca/lerameur/

Everything is supplied by a 12v battery

I am using this cicuit: http://www.kettering.edu/~bguru/EE323/EE323-05.pdf
except for the resisitor to change the frequency.

Ken
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Glenn Gundlach
electronics forum Guru Wannabe


Joined: 30 Apr 2005
Posts: 222

PostPosted: Sun Jul 16, 2006 4:59 pm    Post subject: Re: square waveform (555) Reply with quote
Ken O wrote:
Quote:
"Tim Williams" <tmoranwms@charter.net> wrote in message
news:JOsug.3162$0r6.1663@fe05.lga...
"Ken O" <lera@yahoo.com> wrote in message
news:e9dg5e$nv8$1@nntp.aioe.org...
So usinf a 6v supply, instead of getting 6v high 0v low. I get 6v high,
5.99v, 5.98 ... 5.89, (there is a small slope at the high)

5.89V counts as damned close to 6V if you ask me. You're lucky to get
that much with silicon, a 0.6V drop is more typical (and you'll find it
under a stiffer load).

I don't know why it would drop. It could be real, some effect internal to
the 555, a power supply issue (is +V varying by 0.1V as well?), or
something with your meter, or how you're measuring it.


Ok I put up a web page to show what I get on the scope:
http://www3.sympatico.ca/lerameur/

Everything is supplied by a 12v battery

I am using this cicuit: http://www.kettering.edu/~bguru/EE323/EE323-05.pdf
except for the resisitor to change the frequency.

Ken

Its staring you in the face right in the photo. Put the scope into DC
coupling and check back.

GG
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Sun Jul 16, 2006 7:24 pm    Post subject: Re: square waveform (555) Reply with quote
<stratus46@yahoo.com> wrote in message
news:1153069153.154857.10490@m79g2000cwm.googlegroups.com...
Quote:

Ken O wrote:
"Tim Williams" <tmoranwms@charter.net> wrote in message
news:JOsug.3162$0r6.1663@fe05.lga...
"Ken O" <lera@yahoo.com> wrote in message
news:e9dg5e$nv8$1@nntp.aioe.org...
So usinf a 6v supply, instead of getting 6v high 0v low. I get 6v
high,
5.99v, 5.98 ... 5.89, (there is a small slope at the high)

5.89V counts as damned close to 6V if you ask me. You're lucky to get
that much with silicon, a 0.6V drop is more typical (and you'll find it
under a stiffer load).

I don't know why it would drop. It could be real, some effect internal
to
the 555, a power supply issue (is +V varying by 0.1V as well?), or
something with your meter, or how you're measuring it.


Ok I put up a web page to show what I get on the scope:
http://www3.sympatico.ca/lerameur/

Everything is supplied by a 12v battery

I am using this cicuit:
http://www.kettering.edu/~bguru/EE323/EE323-05.pdf
except for the resisitor to change the frequency.

Ken

Its staring you in the face right in the photo. Put the scope into DC
coupling and check back.

oook , thank you
I feel dumb enough now

K
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Mark Fortune
electronics forum addict


Joined: 06 Jul 2006
Posts: 57

PostPosted: Sun Jul 16, 2006 8:23 pm    Post subject: Re: square waveform (555) Reply with quote
Ken O wrote:
Quote:
stratus46@yahoo.com> wrote in message
news:1153069153.154857.10490@m79g2000cwm.googlegroups.com...

Ken O wrote:

"Tim Williams" <tmoranwms@charter.net> wrote in message
news:JOsug.3162$0r6.1663@fe05.lga...

"Ken O" <lera@yahoo.com> wrote in message
news:e9dg5e$nv8$1@nntp.aioe.org...

So usinf a 6v supply, instead of getting 6v high 0v low. I get 6v
high,
5.99v, 5.98 ... 5.89, (there is a small slope at the high)

5.89V counts as damned close to 6V if you ask me. You're lucky to get
that much with silicon, a 0.6V drop is more typical (and you'll find it
under a stiffer load).

I don't know why it would drop. It could be real, some effect internal
to
the 555, a power supply issue (is +V varying by 0.1V as well?), or
something with your meter, or how you're measuring it.


Ok I put up a web page to show what I get on the scope:
http://www3.sympatico.ca/lerameur/

Everything is supplied by a 12v battery

I am using this cicuit:
http://www.kettering.edu/~bguru/EE323/EE323-05.pdf
except for the resisitor to change the frequency.

Ken

Its staring you in the face right in the photo. Put the scope into DC
coupling and check back.


oook , thank you
I feel dumb enough now

K



Sometimes the hardest things to spot are the most obvious ones.
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Jamie
electronics forum Guru


Joined: 24 Mar 2005
Posts: 597

PostPosted: Mon Jul 17, 2006 1:13 am    Post subject: Re: square waveform (555) Reply with quote
Ken O wrote:

Quote:
Hello everyone,

Just liek to know if it is a normal thing that at LOW frequencies ( 15-25
Hz) that the output of a 555 timer is not exactly a square wave. At higher
frequencies I get a perfect square wave (say between 50 and 300Hz). But at
lower frequencies, the voltage when get to high, slowly decreases until the
output of the 555 turns off.
So usinf a 6v supply, instead of getting 6v high 0v low. I get 6v high,
5.99v, 5.98 ... 5.89, (there is a small slope at the high) then it goes
low to 0v. I am using 50% duty cycle.

I hope I was clear enough
thank you,

ken


maybe your caps in your supply is not holding charge.

test your supply voltage.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
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Google
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