square waveform (555)

[Ken O]

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

 

[Tim Williams]

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

 

[Ken O]

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

 

[[email protected]]

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

 

[Ken O]

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

 

[Mark Fortune]

oook , thank you
I feel dumb enough now

K

Sometimes the hardest things to spot are the most obvious ones.

 

[Jamie]

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.