The 2 ways to make mark & space equal on a 555 astable circu

[John Fields]

On Sun, 28 Jun 2015 11:08:05 -0400, M Philbrook
<jamie_ka1lpa@charter.net> wrote:

In article <35avoa183rm86enfsak3e80s7mvaj939k6@4ax.com>,
jfields@austininstruments.com says...

On Sat, 27 Jun 2015 22:56:59 -0700 (PDT), Phil Allison
pallison49@gmail.com> wrote:

John Fields wrote:

Maynard Philbrook

tie the trigger and threshold together with a R to common and a Cap
from output to this same node.
This will give you a square wave that is close enough.


With the RC wired the way M Philbrook described, the output will
always be a square wave regardless of frequency, and frequency can
be changed by changing the values of either R, or C, or both.


** Maynard's wrong connection does not work.

All it creates is high frequency squegging or nothing.



... Phil

---
You're right; can't imagine what I was thinking...

Thanks for the reality check.

John Fields

Oh excuse me for not looking closer, the connects are correct, I
just had the two components switched around.

---
You're trying to squirm out of the enormity of your error by trying
to trivialize it; good thing you weren't an American pilot flying
for the Queen during the battle of Britain.
---

Either way, they both produce 50% duty cycle. One rounded corners at
high freq max to the chip operatin and the other square at RC freq..

---
I don't believe the request was for a high fixed-frequency square
wave oscillator with a frequency determined by 555 internals, it was
for a square wave oscillator with a frequency determined by an RC.
---

> I do make misakes at times. At least I can admit to it.

---
When the "misake" is as apparent as the nose on your face, and
you've been defeated, what makes you think it's magnanimous to
acknowledge the error when you have no other choice?

Too bad you're not old school Japanese.

John Fields

 

[Phil Allison]

John Fields wrote:

---
You're trying to squirm out of the enormity of your error by trying
to trivialize it; good thing you weren't an American pilot flying
for the Queen during the battle of Britain.
---

** That reference is a *tad* obscure !!

There were about a dozen American born pilots who flew in the Battle of Britain against the Luftwaffe. However, most had to lie about their US nationality and pretend to be Canadian to get the chance. US citizens were bound by a "Neutrality Act" that prohibited them joining a foreign armed service.

Citizens of other countries like Australia plus those places already invaded had no such problem, cos they had already declared war on Germany.

The USA did not do the same until the Imperial Japanese Navy attack on Pearl Harbour forced the issue and Germany declared war on the USA.




... Phil

 

[John Fields]

On Mon, 29 Jun 2015 03:03:31 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

John Fields wrote:


---
You're trying to squirm out of the enormity of your error by trying
to trivialize it; good thing you weren't an American pilot flying
for the Queen during the battle of Britain.
---

** That reference is a *tad* obscure !!

---
He got the connection about pumping bullets into airplanes right,
but was confused about whether the target was a cross or a bulls
eye.
---

There were about a dozen American born pilots who flew in the Battle of Britain against the Luftwaffe. However, most had to lie about their US nationality and pretend to be Canadian to get the chance. US citizens were bound by a "Neutrality Act" that prohibited them joining a foreign armed service.

Citizens of other countries like Australia plus those places already invaded had no such problem, cos they had already declared war on Germany.

The USA did not do the same until the Imperial Japanese Navy attack on Pearl Harbour forced the issue and Germany declared war on the USA.




... Phil

 

[Jim Thompson]

On Mon, 29 Jun 2015 01:24:34 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Sun, 28 Jun 2015 11:08:05 -0400, M Philbrook
jamie_ka1lpa@charter.net> wrote:

[snip]

I do make misakes at times. At least I can admit to it.

---
When the "misake" is as apparent as the nose on your face, and
you've been defeated, what makes you think it's magnanimous to
acknowledge the error when you have no other choice?

Too bad you're not old school Japanese.

John Fields

Sno-o-o-o-ort >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Michael A. Terrell]

Michael Black wrote:

Michael A. Terrell wrote:

I haven't used the 4020 since the '80s, but I remembered that it was
a multi stage ripple counter.

Yes it is. But some of those long ripple counters didn't have all the
outputs available, though I can't remember if that was the 4020 or the
4060. And as someone pointed out, it is the 4060 that had the built in
oscillator.

Both of those are 14 stage, and are missing two outputs, The 4040 is
a 12 stage, and has all 12 outputs available.

I think I missed something there. I bet the ICM7242 that somebody
mentioned is just the XR timer I was thinking of but from a different
manufacturer and hence a variant on the number.

The XR had some feedback, so if that output changed states, you could stop
the oscillator, or something like that. So it was a more integrated
concept than just an oscillator with a divider chain.

I built a four digit, digital lock with just a 4017, and one transistor
sometime in the '80s. I was told that it couldn't be done, so I had to
do it.

 

[M Philbrook]

In article <qfo1pahg5rtt9fc413echn943c64nbgipp@4ax.com>,
jfields@austininstruments.com says...

I do make misakes at times. At least I can admit to it.

---
When the "misake" is as apparent as the nose on your face, and
you've been defeated, what makes you think it's magnanimous to
acknowledge the error when you have no other choice?

Too bad you're not old school Japanese.

John Fields

Just when I thought you were getting civil, another
mastake on my part I guess.

You really do fit the Dunning Kruger example.

Go screw yourself.

Jamie

 

[John Fields]

On Mon, 29 Jun 2015 19:08:14 -0400, M Philbrook
<jamie_ka1lpa@charter.net> wrote:

In article <qfo1pahg5rtt9fc413echn943c64nbgipp@4ax.com>,
jfields@austininstruments.com says...

I do make misakes at times. At least I can admit to it.

---
When the "misake" is as apparent as the nose on your face, and
you've been defeated, what makes you think it's magnanimous to
acknowledge the error when you have no other choice?

Too bad you're not old school Japanese.

John Fields



Just when I thought you were getting civil, another
mastake on my part I guess.

---
Interestingly, you equate civility with agreement, and thought I was
"coming around" when I glossed over your 555 gaffe and sided with
you on your circuit thoughts.

Thanks to Phil Allison's critique of my agreement, I realized I'd
made a mistake in evaluating your circuit properly in the first
place, owned up to it, and the next thing I read, from you, was some
whining about that you'd gotten the connections right but swapped
the parts, as if that were some excuse for the error.

I'm not an uncivil person, but I do tend to return genuine abuse
vehemently in an effort to avoid becoming embroiled in what would
become - with the likes of you in it - merely a banal and plodding
ember war.
---

> You really do fit the Dunning Kruger example.

---
Coming from the patient, I'd expect that kind of retort.
---

Go screw yourself.

Jamie

---
Ahh...

The cherry on top of the [hot fudge] sundae!

John Fields

 

[Adam Funk]

On 2015-06-25, Jasen Betts wrote:

On 2015-06-25, Adam Funk <a24061@ducksburg.com> wrote:
http://www.electronics-tutorials.ws/waveforms/555_oscillator.html

From this link & other places, I see there are (at least) 2 ways to
make the 555 astable circuit produce a square wave with a 50% duty
cycle:

* putting 2 diodes into the circuit & using the same resistance
from Vcc to discharge as from discharge to trigger & threshold, as
shown in the "Improved 555 Oscillator Duty Cycle"

* ignoring the discharge pin as shown in "50% Duty Cycle Astable
Oscillator"

Is there ever any advantage to using the first version (with more
components)?

Second version only works correctly with CMOS 555s it comes comes
close-ish with regular 555s but comes out a bit low. If the supply
voltage is fixed this can be corrected by tweaking with an additional
resistor.

By "a bit low", you mean the duty cycle ends up less than 50%?


--
I was born, lucky me, in a land that I love.
Though I'm poor, I am free.
When I grow I shall fight; for this land I shall die.
May the sun never set. --- The Kinks

 

[Adam Funk]

On 2015-06-25, Michael Black wrote:

The way I remember it, the diode scheme came from Signetics, so that
appeared first.

The one where the capacitor is charged and discharged via pin 3 and a
single resistor, that was in "Engineer's Notebook" or "Designer's
Casebook" (or maybe I have those jumbled) in "Electronics" magazine, just
a circuit and a small description, sometime in the early seventies.

I've always used that circuit with the resistor from pin 3 since I saw
that bit in "Electronics", it's just so much simpler unless you need
something more complicated.

On the other hand, some have pointed out that the original 555 isn't
perfect in this regard, the scheme works better with the CMOS 555. So that might
factor in if you had some very specific need for exact 50% duty cycle.
The original circuit in "Electronics" was for the original 555, though if
I remember properly, they also had a pullup resistor on pin 3 (but I've
never bothered with that).

I would point out that if someone needs an exact 50% duty cycle, it's just
as easy to put the signal through a divider to get that 50%, and digital
is often simpler than analog.

Interesting, thanks. Accuracy of the duty cycle isn't important here
(it's just to make audible tones).

 

[Adam Funk]

On 2015-06-25, Jim Thompson wrote:

On Thu, 25 Jun 2015 11:40:03 +0100, Adam Funk <a24061@ducksburg.com
wrote:

http://www.electronics-tutorials.ws/waveforms/555_oscillator.html

From this link & other places, I see there are (at least) 2 ways to
make the 555 astable circuit produce a square wave with a 50% duty
cycle:

* putting 2 diodes into the circuit & using the same resistance
from Vcc to discharge as from discharge to trigger & threshold, as
shown in the "Improved 555 Oscillator Duty Cycle"

* ignoring the discharge pin as shown in "50% Duty Cycle Astable
Oscillator"

Is there ever any advantage to using the first version (with more
components)?

Thanks.

There's an even easier way (at least for the CMOS version). The
charge/discharge resistor is driven from the output pin.

Isn't that what's shown in the 2nd diagram I referred to? Maybe not
very clearly, since there aren't any figure numbers on the web page,
but this one:

<http://www.electronics-tutorials.ws/waveforms/tim58a.gif?81223b>

Pin 3 is connected to the resistor and provides the output.


--
....the reason why so many professional artists drink a lot is not
necessarily very much to do with the artistic temperament, etc. It is
simply that they can afford to, because they can normally take a large
part of a day off to deal with the ravages. [Amis _On Drink_]

 

[Adam Funk]

On 2015-06-25, Jim Thompson wrote:

For frequency _and_ duty-cycle control see Freq_Duty_555.pdf on the
S.E.D/Schematics Page of my website.

Thanks for bringing that page to my attention; there's quite a lot of
interesting stuff there.


--
We do not debug. Our software does not coddle the weak. Bugs
are good for building character in the user.
--- Klingon Programmer's Guide

 

[Michael Black]

On Wed, 1 Jul 2015, Adam Funk wrote:

On 2015-06-25, Michael Black wrote:

The way I remember it, the diode scheme came from Signetics, so that
appeared first.

The one where the capacitor is charged and discharged via pin 3 and a
single resistor, that was in "Engineer's Notebook" or "Designer's
Casebook" (or maybe I have those jumbled) in "Electronics" magazine, just
a circuit and a small description, sometime in the early seventies.

I've always used that circuit with the resistor from pin 3 since I saw
that bit in "Electronics", it's just so much simpler unless you need
something more complicated.

On the other hand, some have pointed out that the original 555 isn't
perfect in this regard, the scheme works better with the CMOS 555. So that might
factor in if you had some very specific need for exact 50% duty cycle.
The original circuit in "Electronics" was for the original 555, though if
I remember properly, they also had a pullup resistor on pin 3 (but I've
never bothered with that).

I would point out that if someone needs an exact 50% duty cycle, it's just
as easy to put the signal through a divider to get that 50%, and digital
is often simpler than analog.

Interesting, thanks. Accuracy of the duty cycle isn't important here
(it's just to make audible tones).

Once I saw the circuit in "Electronics", I never fussed with the two
resistor setup (unless I needed something specific). When I was
breadboarding, it was always so much easier to just use the resistor from
the output.

Michael

 

[Michael Black]

On Wed, 1 Jul 2015, Adam Funk wrote:

On 2015-06-25, Jasen Betts wrote:

On 2015-06-25, Adam Funk <a24061@ducksburg.com> wrote:
http://www.electronics-tutorials.ws/waveforms/555_oscillator.html

From this link & other places, I see there are (at least) 2 ways to
make the 555 astable circuit produce a square wave with a 50% duty
cycle:

* putting 2 diodes into the circuit & using the same resistance
from Vcc to discharge as from discharge to trigger & threshold, as
shown in the "Improved 555 Oscillator Duty Cycle"

* ignoring the discharge pin as shown in "50% Duty Cycle Astable
Oscillator"

Is there ever any advantage to using the first version (with more
components)?

Second version only works correctly with CMOS 555s it comes comes
close-ish with regular 555s but comes out a bit low. If the supply
voltage is fixed this can be corrected by tweaking with an additional
resistor.

By "a bit low", you mean the duty cycle ends up less than 50%?

There are things where you need 50% duty cycle. I have no idea whether
the non-CMOS 555 is "good enough" for that.

But, it's perfect for when you want a simple oscillator and you want a
reasonably square wave output.

For most uses, it's fine.

Michael

 

[M Philbrook]

In article <au6d6cxov4.ln2@news.ducksburg.com>, a24061@ducksburg.com
says...

On 2015-06-25, Michael Black wrote:

The way I remember it, the diode scheme came from Signetics, so that
appeared first.

The one where the capacitor is charged and discharged via pin 3 and a
single resistor, that was in "Engineer's Notebook" or "Designer's
Casebook" (or maybe I have those jumbled) in "Electronics" magazine, just
a circuit and a small description, sometime in the early seventies.

I've always used that circuit with the resistor from pin 3 since I saw
that bit in "Electronics", it's just so much simpler unless you need
something more complicated.

On the other hand, some have pointed out that the original 555 isn't
perfect in this regard, the scheme works better with the CMOS 555. So that might
factor in if you had some very specific need for exact 50% duty cycle.
The original circuit in "Electronics" was for the original 555, though if
I remember properly, they also had a pullup resistor on pin 3 (but I've
never bothered with that).

I would point out that if someone needs an exact 50% duty cycle, it's just
as easy to put the signal through a divider to get that 50%, and digital
is often simpler than analog.

Interesting, thanks. Accuracy of the duty cycle isn't important here
(it's just to make audible tones).

all this commotion and all you wanted was a basic audio tone?

Look up Audio phase shift oscillator circuits.
https://en.wikipedia.org/wiki/Phase-shift_oscillator

Jamie

 

[Michael Black]

On Thu, 2 Jul 2015, M Philbrook wrote:

In article <au6d6cxov4.ln2@news.ducksburg.com>, a24061@ducksburg.com
says...

On 2015-06-25, Michael Black wrote:

The way I remember it, the diode scheme came from Signetics, so that
appeared first.

The one where the capacitor is charged and discharged via pin 3 and a
single resistor, that was in "Engineer's Notebook" or "Designer's
Casebook" (or maybe I have those jumbled) in "Electronics" magazine, just
a circuit and a small description, sometime in the early seventies.

I've always used that circuit with the resistor from pin 3 since I saw
that bit in "Electronics", it's just so much simpler unless you need
something more complicated.

On the other hand, some have pointed out that the original 555 isn't
perfect in this regard, the scheme works better with the CMOS 555. So that might
factor in if you had some very specific need for exact 50% duty cycle.
The original circuit in "Electronics" was for the original 555, though if
I remember properly, they also had a pullup resistor on pin 3 (but I've
never bothered with that).

I would point out that if someone needs an exact 50% duty cycle, it's just
as easy to put the signal through a divider to get that 50%, and digital
is often simpler than analog.

Interesting, thanks. Accuracy of the duty cycle isn't important here
(it's just to make audible tones).

all this commotion and all you wanted was a basic audio tone?

Look up Audio phase shift oscillator circuits.
https://en.wikipedia.org/wiki/Phase-shift_oscillator

The 555 is simpler.

If you use a transistor, if it doesn't have enough gain the circuit won't
oscillate.

It's certainly not simple to tune to different frequencies.

A square wave may sound better to the ear when testing something, and
having harmonics may be an advantage in some cases.

Any signal injector circuit I've seen uses a square wave of some kind,
never a sine wave.

Michael

 

[Adam Funk]

On 2015-07-03, M Philbrook wrote:

In article <au6d6cxov4.ln2@news.ducksburg.com>, a24061@ducksburg.com
says...

Interesting, thanks. Accuracy of the duty cycle isn't important here
(it's just to make audible tones).

all this commotion and all you wanted was a basic audio tone?

I wasn't expecting the commotion!


--
If hard data were the filtering criterion you could fit the entire
contents of the Internet on a floppy disk. --- Cecil Adams

 

[Adam Funk]

On 2015-07-01, Michael Black wrote:

On Wed, 1 Jul 2015, Adam Funk wrote:

On 2015-06-25, Jasen Betts wrote:

On 2015-06-25, Adam Funk <a24061@ducksburg.com> wrote:
http://www.electronics-tutorials.ws/waveforms/555_oscillator.html

From this link & other places, I see there are (at least) 2 ways to
make the 555 astable circuit produce a square wave with a 50% duty
cycle:

* putting 2 diodes into the circuit & using the same resistance
from Vcc to discharge as from discharge to trigger & threshold, as
shown in the "Improved 555 Oscillator Duty Cycle"

* ignoring the discharge pin as shown in "50% Duty Cycle Astable
Oscillator"

Is there ever any advantage to using the first version (with more
components)?

Second version only works correctly with CMOS 555s it comes comes
close-ish with regular 555s but comes out a bit low. If the supply
voltage is fixed this can be corrected by tweaking with an additional
resistor.

By "a bit low", you mean the duty cycle ends up less than 50%?

There are things where you need 50% duty cycle. I have no idea whether
the non-CMOS 555 is "good enough" for that.

But, it's perfect for when you want a simple oscillator and you want a
reasonably square wave output.

For most uses, it's fine.

Thanks.


--
Our scientific power has outrun our spiritual power. We have guided
missiles and misguided men. --- Martin Luther King, Jr.

 

[Michael Black]

On Fri, 3 Jul 2015, Adam Funk wrote:

On 2015-07-03, M Philbrook wrote:

In article <au6d6cxov4.ln2@news.ducksburg.com>, a24061@ducksburg.com
says...

Interesting, thanks. Accuracy of the duty cycle isn't important here
(it's just to make audible tones).

all this commotion and all you wanted was a basic audio tone?

I wasn't expecting the commotion!

It wasn't commotion.

You asked a question that was very clear, wondering about one of two
options.

You didn't post a vague question that could be interpreted multiple ways,
which so often gets endless replies, nobody really knowing what the
question was.

You didnt' ask about something specific because you "knew" it was the
solution, only for us to discover half-way down a long thread that what
you'd asked for wasn't the right solution for the problem (in part because
the problem wasn't mentioned until well into the thread) Those can be fun
threads, since some take the post literally, and then it turns out the
original poster just thought they knew what they needed.

I remember one cross-posted thread that went on forever, each iteration
changing the end goal, with side issues like "varactors can't multiply
frequencies" and then finally the actual use was revealed, which changed
the solution drastically since the specs for that were pretty simple. If
he'd asked in one of the two crossposted newsgroups, he would have gotten
two different answers depending on the newsgroup, but I suspect one would
have come to the answer sooner.

No, this was a simple question, the only "debate" over whether "50% duty
cycle" meant literally or "just close".

And the question has come up before, "well that won't work unless you use
the CMOS 555" which is true if you need that exact 50% duty cycle, but for
most use, it doesnt' have to be exact. Another time when people took the
question literally.

Michael

 

[John Fields]

On Thu, 25 Jun 2015 11:40:03 +0100, Adam Funk <a24061@ducksburg.com>
wrote:

http://www.electronics-tutorials.ws/waveforms/555_oscillator.html

From this link & other places, I see there are (at least) 2 ways to
make the 555 astable circuit produce a square wave with a 50% duty
cycle:

* putting 2 diodes into the circuit & using the same resistance
from Vcc to discharge as from discharge to trigger & threshold, as
shown in the "Improved 555 Oscillator Duty Cycle"

* ignoring the discharge pin as shown in "50% Duty Cycle Astable
Oscillator"

Is there ever any advantage to using the first version (with more
components)?

Thanks.

---
Yes.

If you substitute a pot for the two timing resistors you can get
from near zero to near 100% duty cycle control without affecting the
frequency (much...).

Version 4
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SYMATTR InstName R1
SYMATTR Value 40k
SYMBOL res -112 128 M0
SYMATTR InstName R2
SYMATTR Value 40k
SYMBOL res -112 336 M0
SYMATTR InstName R9
SYMATTR Value 10k
SYMBOL voltage -256 -64 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V3
SYMATTR Value 2
TEXT 440 176 Left 2 ;1
TEXT 440 240 Left 2 ;2
TEXT 440 304 Left 2 ;3
TEXT 440 360 Left 2 ;4
TEXT 184 368 Left 2 ;5
TEXT 184 304 Left 2 ;6
TEXT 184 240 Left 2 ;7
TEXT 184 176 Left 2 ;8
TEXT -56 608 Right 2 !.tran 2 startup uic
TEXT 440 -496 Left 2 ;1
TEXT 440 -432 Left 2 ;2
TEXT 440 -368 Left 2 ;3
TEXT 440 -312 Left 2 ;4
TEXT 184 -304 Left 2 ;5
TEXT 184 -368 Left 2 ;6
TEXT 184 -432 Left 2 ;7
TEXT 184 -496 Left 2 ;8

 

[Adam Funk]

On 2015-07-03, Michael Black wrote:

You asked a question that was very clear, wondering about one of two
options.

You didn't post a vague question that could be interpreted multiple ways,
which so often gets endless replies, nobody really knowing what the
question was.

You didnt' ask about something specific because you "knew" it was the
solution, only for us to discover half-way down a long thread that what
you'd asked for wasn't the right solution for the problem (in part because
the problem wasn't mentioned until well into the thread) Those can be fun
threads, since some take the post literally, and then it turns out the
original poster just thought they knew what they needed.

I remember one cross-posted thread that went on forever, each iteration
changing the end goal, with side issues like "varactors can't multiply
frequencies" and then finally the actual use was revealed, which changed
the solution drastically since the specs for that were pretty simple. If
he'd asked in one of the two crossposted newsgroups, he would have gotten
two different answers depending on the newsgroup, but I suspect one would
have come to the answer sooner.

No, this was a simple question, the only "debate" over whether "50% duty
cycle" meant literally or "just close".

And the question has come up before, "well that won't work unless you use
the CMOS 555" which is true if you need that exact 50% duty cycle, but for
most use, it doesnt' have to be exact. Another time when people took the
question literally.

Thanks!


--
Specifications are for the weak & timid!
--- Klingon Programmer's Guide