What happened to Phil Allison?

Bill Sloman wrote:
On Aug 30, 5:07 am, ehsjr <eh...@nospamverizon.net> wrote:
Bill Sloman wrote:

snip
The catch with the 555 is that it combines a part nobody really ought
to use these days - a monostable - with a rather poor quality bipolar
power transistor, and uses the same ground return pin for both
devices. There are a few situations where these defects aren't
troublesome, but modern designers tend to make their time control
signals in the digital domain, and use then to drive a MOSFET switch.

There's still a place in the world for monostables. As long as you
don't care if the timing is off by a factor of 2 either way, they work
fine. And obsolescent or not, the 555 will very likely still be
available after today's latest magic micro is gone. It also doesn't
need programming support. Monostables are good for pulse stretching,
for instance, where you don't know when the pulse is going to arrive
with respect to the uC clock.

I recently did a laser locker (using both current and temperature tuning
to get wide range and good bandwidth) that was almost all analogue,
including two feedback loops, laser and Peltier current drivers, and a
triangular sweep for lock acquisition. It does need a small micro off
on one corner to mind the store, but nothing more than that. You turn
the thing on, and a few seconds later the laser is in lock, with a
linewidth that should be less than 100 Hz.

If the projected volume were greater, it would be worth implementing
some of that in a uC, but nothing like all of it.

Make something work with one implementation or another of one or two
555s and lack of a microprocessor, and it generally costs less than using
a microprocessor. Much of the time, the story is the same if the
alternative to the 555 is an op-amp or basic logic ICs. 555s are also
smaller and have fewer pins than logic ICs generally have, and it's my
favorite Schmidt trigger inverting buffer when I only need one rather
than 2-6. It even has a wider and more predictable hysteresis range than
the 40106.

On Aug 30, 10:59 am, Bill Bowden <wrongaddr...@att.net> wrote:

On Aug 29, 12:07 pm, ehsjr <eh...@nospamverizon.net> wrote:






Bill Sloman wrote:

snip

That is the wording that that you would have preferred that I used.
Everybody's opinion of the reliability of their knowledge is
fundamentally subjective, but my data-base has been being tested
against reality for some fifty years now, and has proved to be pretty
reliable.

You seem to have stopped testing yours against reality around the time
the 555 became obsolescent, which would be about thirty years ago.

Hmmm. A search in Mouser for the 555 yields 6 pages. On the
first page alone you'll find that there are 152,667 555s in
stock. Searching for 555s in Digikey yields 4 pages of results,
all in stock. The quantity on the first page alone totally
swamps the Mouser quantities - well over 400,000 in stock.

Mouser and Digikey (and others) seem to have a better grip on
reality than you do, focusing on the viability of the part,
rather than what you see as its "obsolence".

Ed

Bill Sloman, Nijmegen

There are also SMD versions of the 555, so it must have current
applications..


John Fields isn't the only engineer who is still repeating what worked
for him forty years ago. It doesn't make the 555 (or the 741) any less
obsolete.

--
Bill Sloman, Nijmegen
Ok, so lets stop using resistors, caps, potentiometers and so on.

In article <4C7BE0D4.1050...@electrooptical.net>, Phil Hobbs wrote:
Bill Sloman wrote:
On Aug 30, 5:07 am, ehsjr <eh...@nospamverizon.net> wrote:
Bill Sloman wrote:

snip
The catch with the 555 is that it combines a part nobody really ought
to use these days - a monostable - with a rather poor quality bipolar
power transistor, and uses the same ground return pin for both
devices. There are a few situations where these defects aren't
troublesome, but modern designers tend to make their time control
signals in the digital domain, and use then to drive a MOSFET switch.

There's still a place in the world for monostables.  As long as you
don't care if the timing is off by a factor of 2 either way, they work
fine.  And obsolescent or not, the 555 will very likely still be
available after today's latest magic micro is gone.  It also doesn't
need programming support.   Monostables are good for pulse stretching,
for instance, where you don't know when the pulse is going to arrive
with respect to the uC clock.

I recently did a laser locker (using both current and temperature tuning
to get wide range and good bandwidth) that was almost all analogue,
including two feedback loops, laser and Peltier current drivers, and a
triangular sweep for lock acquisition.    It does need a small micro off
on one corner to mind the store, but nothing more than that.  You turn
the thing on, and a few seconds later the laser is in lock, with a
linewidth that should be less than 100 Hz.

If the projected volume were greater, it would be worth implementing
some of that in a uC, but nothing like all of it.

  How about projects that are simpler and where parts count and cost
is important almost to or outright to pennies?

  Make something work with one implementation or another of one or two
555s and lack of a microprocessor, and it generally costs less than using
a microprocessor.  Much of the time, the story is the same if the
alternative to the 555 is an op-amp or basic logic ICs.  555s are also
smaller and have fewer pins than logic ICs generally have, and it's my
favorite Schmidt trigger inverting buffer when I only need one rather
than 2-6.  It even has a wider and more predictable hysteresis range than
the 40106.

On Aug 31, 3:23 am, d...@manx.misty.com (Don Klipstein) wrote:
In article <4C7BE0D4.1050...@electrooptical.net>, Phil Hobbs wrote:
Bill Sloman wrote:
On Aug 30, 5:07 am, ehsjr <eh...@nospamverizon.net> wrote:
Bill Sloman wrote:
snip
The catch with the 555 is that it combines a part nobody really ought
to use these days - a monostable - with a rather poor quality bipolar
power transistor, and uses the same ground return pin for both
devices. There are a few situations where these defects aren't
troublesome, but modern designers tend to make their time control
signals in the digital domain, and use then to drive a MOSFET switch.
There's still a place in the world for monostables. As long as you
don't care if the timing is off by a factor of 2 either way, they work
fine. And obsolescent or not, the 555 will very likely still be
available after today's latest magic micro is gone. It also doesn't
need programming support. Monostables are good for pulse stretching,
for instance, where you don't know when the pulse is going to arrive
with respect to the uC clock.

A delay line is better, if the pulse stretching you want fits into a
delay line you can make or buy.

On Aug 31, 11:26 am, Phil Hobbs
pcdhSpamMeSensel...@electrooptical.net> wrote:
Bill Sloman wrote:
On Aug 31, 3:23 am, d...@manx.misty.com (Don Klipstein) wrote:
In article <4C7BE0D4.1050...@electrooptical.net>, Phil Hobbs wrote:
Bill Sloman wrote:
On Aug 30, 5:07 am, ehsjr <eh...@nospamverizon.net> wrote:
Bill Sloman wrote:
snip
The catch with the 555 is that it combines a part nobody really ought
to use these days - a monostable - with a rather poor quality bipolar
power transistor, and uses the same ground return pin for both
devices. There are a few situations where these defects aren't
troublesome, but modern designers tend to make their time control
signals in the digital domain, and use then to drive a MOSFET switch..
There's still a place in the world for monostables. As long as you
don't care if the timing is off by a factor of 2 either way, they work
fine. And obsolescent or not, the 555 will very likely still be
available after today's latest magic micro is gone. It also doesn't
need programming support. Monostables are good for pulse stretching,
for instance, where you don't know when the pulse is going to arrive
with respect to the uC clock.
A delay line is better, if the pulse stretching you want fits into a
delay line you can make or buy.
Why? What's the performance gain, in exchange for using a more
expensive, less general, and less common part?

A monostable is a circuit that produces a slowly rising ramp and
compares the ramp voltage with some kind of reference voltage. Your
monostable period ends when the comparator fires (for the first time).
Any noise on either the ramp or the reference adds jitter to the
period. Currents circulating through your ground and power supply
rails have a nasty tendency to contribute to that noise. Careful
layout can minimise - but not eliminate - this. Delay lines do tend to
degrade the edge speed of transitions launched into them, but you
still tend end up with much higher volts per microsecond that you get
with a monostable's ramp.

I can't remember ever having designed a 555 into any actual product, but
I've often used them when hacking something together in a die cast box
for lab use. Quick, simple, no problems. Some of those boxes have been
in use for 20 years, off and on, with various modifications along the way.

A legacy part in a legacy design. Minimal expenditure on design,
poorer performance than a more thorough approach would have yielded.
Doesn't make the 555 any less obsolete.

Bill Sloman wrote:
On Aug 31, 3:23 am, d...@manx.misty.com (Don Klipstein) wrote:
In article <4C7BE0D4.1050...@electrooptical.net>, Phil Hobbs wrote:
Bill Sloman wrote:
On Aug 30, 5:07 am, ehsjr <eh...@nospamverizon.net> wrote:
Bill Sloman wrote:
snip
The catch with the 555 is that it combines a part nobody really ought
to use these days - a monostable - with a rather poor quality bipolar
power transistor, and uses the same ground return pin for both
devices. There are a few situations where these defects aren't
troublesome, but modern designers tend to make their time control
signals in the digital domain, and use then to drive a MOSFET switch..
There's still a place in the world for monostables.  As long as you
don't care if the timing is off by a factor of 2 either way, they work
fine.  And obsolescent or not, the 555 will very likely still be
available after today's latest magic micro is gone.  It also doesn't
need programming support.   Monostables are good for pulse stretching,
for instance, where you don't know when the pulse is going to arrive
with respect to the uC clock.

A delay line is better, if the pulse stretching you want fits into a
delay line you can make or buy.

Why?  What's the performance gain, in exchange for using a more
expensive, less general, and less common part?

I can't remember ever having designed a 555 into any actual product, but
I've often used them when hacking something together in a die cast box
for lab use.  Quick, simple, no problems.  Some of those boxes have been
  in use for 20 years, off and on, with various modifications along the way.

On Mon, 30 Aug 2010 17:23:13 +0000 (UTC), d...@manx.misty.com (Don

Klipstein) wrote:

 Make something work with one implementation or another of one or two
555s and lack of a microprocessor, and it generally costs less than using
a microprocessor.  Much of the time, the story is the same if the
alternative to the 555 is an op-amp or basic logic ICs.  555s are also
smaller and have fewer pins than logic ICs generally have, and it's my
favorite Schmidt trigger inverting buffer when I only need one rather
than 2-6.  It even has a wider and more predictable hysteresis range than
the 40106.

---
Yup, I'd be willing to bet that Dr. Camenzind is flabbergasted, and
immensely pleased, with the ways his baby has been put to work.

One particularly cute application which passed through here a while
back was with someone who was looking to drive an audio transducer at
a higher level than could be afforded by a single transistor doing
Morse "H" forever, and someone suggested using a couple of 555's with
their totem poles arranged as a full bridge, thereby driving the
transducer with about about four times the power available from the
single transistor, at the same supply voltage.

I remember that he posted back, not quite awestruck, but certainly
quite impressed with the performance increase he enjoyed from his
transducer for certainly less than a dollar's worth of parts.

On Aug 31, 9:25 am, John Fields <jfie...@austininstruments.com> wrote:
On Mon, 30 Aug 2010 17:23:13 +0000 (UTC), d...@manx.misty.com (Don

Klipstein) wrote:

 Make something work with one implementation or another of one or two
555s and lack of a microprocessor, and it generally costs less than using
a microprocessor.  Much of the time, the story is the same if the
alternative to the 555 is an op-amp or basic logic ICs.  555s are also
smaller and have fewer pins than logic ICs generally have, and it's my
favorite Schmidt trigger inverting buffer when I only need one rather
than 2-6.  It even has a wider and more predictable hysteresis range than
the 40106.

---
Yup, I'd be willing to bet that Dr. Camenzind is flabbergasted, and
immensely pleased, with the ways his baby has been put to work.

If you'd read his book - which you can now download for free

http://www.designinganalogchips.com/

you know that chapter 11 discusses the 555 in detail, and how the
circuit could be improved. He's certainly proud of the design, but
he's - tellingly - particularly proud of being able to fit it into an
8-pin package, which was the primary contributor to its commercial
success.

One particularly cute application which passed through here a while
back was with someone who was looking to drive an audio transducer at
a higher level than could be afforded by a single transistor doing
Morse "H" forever, and someone suggested using a couple of 555's with
their totem poles arranged as a full bridge, thereby driving the
transducer with about about four times the power available from the
single transistor, at the same supply voltage.

I remember that he posted back, not quite awestruck, but certainly
quite impressed with the performance increase he enjoyed from his
transducer for certainly less than a dollar's worth of parts.

Another of the 101 things a boy can do with a 555.

I doubt if this was
the only way of solving that poster's problem, and I'd be surprised if
it was the minimum solution, but since you haven't specified the
problem solved in any detail, this is pure speculation.

IIRR the 555's totem pole output doesn't get all that close to the
positive rail, so "four times the power available" may be something of
an exaggeration.

On Mon, 30 Aug 2010 18:58:11 -0700 (PDT), Bill Sloman



bill.slo...@ieee.org> wrote:
On Aug 31, 9:25 am, John Fields <jfie...@austininstruments.com> wrote:
On Mon, 30 Aug 2010 17:23:13 +0000 (UTC), d...@manx.misty.com (Don

Klipstein) wrote:

 Make something work with one implementation or another of one or two
555s and lack of a microprocessor, and it generally costs less than using
a microprocessor.  Much of the time, the story is the same if the
alternative to the 555 is an op-amp or basic logic ICs.  555s are also
smaller and have fewer pins than logic ICs generally have, and it's my
favorite Schmidt trigger inverting buffer when I only need one rather
than 2-6.  It even has a wider and more predictable hysteresis range than
the 40106.

---
Yup, I'd be willing to bet that Dr. Camenzind is flabbergasted, and
immensely pleased, with the ways his baby has been put to work.

If you'd read his book - which you can now download for free

http://www.designinganalogchips.com/

you know that chapter 11 discusses the 555 in detail, and how the
circuit could be improved. He's certainly proud of the design, but
he's - tellingly - particularly proud of being able to fit it into an
8-pin package, which was the primary contributor to its commercial
success.

---
Your point being???
---

One particularly cute application which passed through here a while
back was with someone who was looking to drive an audio transducer at
a higher level than could be afforded by a single transistor doing
Morse "H" forever, and someone suggested using a couple of 555's with
their totem poles arranged as a full bridge, thereby driving the
transducer with about about four times the power available from the
single transistor, at the same supply voltage.

I remember that he posted back, not quite awestruck, but certainly
quite impressed with the performance increase he enjoyed from his
transducer for certainly less than a dollar's worth of parts.

Another of the 101 things a boy can do with a 555.

---
And you can do what?

About three?
---

I doubt if this was
the only way of solving that poster's problem, and I'd be surprised if
it was the minimum solution, but since you haven't specified the
problem solved in any detail, this is pure speculation.

---
... "it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing."

As is about 90% of what you write.

There's enough detail there for someone skilled in the art to be able
to flesh out a solution.

Of course that puts you at a disadvantage, so your only recourse is to
malign, instead of showing your minimalist "solution".
---

IIRR the 555's totem pole output doesn't get all that close to the
positive rail, so "four times the power available" may be something of
an exaggeration.

---
How so?

If the single transistor driving the load was a single 555's totem
pole emitter follower, then using two 555's in a full bridge, with the
same drop in each emitter follower, would result in about four times
the power dissipated in the load than in the case with a single 555.

Besides, what is it you don't understand about "about"?

On Aug 30, 5:07 am, ehsjr <eh...@nospamverizon.net> wrote:

BillSlomanwrote:

snip



That is the wording that that you would have preferred that I used.
Everybody's opinion of the reliability of their knowledge is
fundamentally subjective, but my data-base has been being tested
against reality for some fifty years now, and has proved to be pretty
reliable.

You seem to have stopped testing yours against reality around the time
the 555 became obsolescent, which would be about thirty years ago.

Hmmm. A search in Mouser for the 555 yields 6 pages. On the
first page alone you'll find that there are 152,667 555s in
stock. Searching for 555s in Digikey yields 4 pages of results,
all in stock. The quantity on the first page alone totally
swamps the Mouser quantities - well over 400,000 in stock.

Mouser and Digikey (and others) seem to have a better grip on
reality than you do, focusing on the viability of the part,
rather than what you see as its "obsolence".


The 555 is a legacy part - like the the 741 - and still sells in large
numbers. When the 555 was introduced it did provide a compact and
adequate solution to a commonly encountered problem, and was designed
into a lot of products. Some of these are still in production.

As with all frequently used parts, it is still beoing incoprporated
into new designs. Hobbyists and amateurs copy old designs, because
they know - or at least fondly believe - that they work, and don't
know enough to design anything better.

Some professional designers - like John Fields - who should know
better, still design around legacy parts, because it lets them recycle
old designs which they know to be reliable. If you are designing
something in a hurry, or don't want to risk designing something that
you can't be sure will work out of the box, using familiar - if
obsolete - parts can be a good short term strategy.

The catch with the 555 is that it combines a part nobody really ought
to use these days - a monostable - with a rather poor quality bipolar
power transistor, and uses the same ground return pin for both
devices. There are a few situations where these defects aren't
troublesome, but modern designers tend to make their time control
signals in the digital domain, and use then to drive a MOSFET switch.

--
Bill Sloman, Nijmegen

In <81685886-6c51-405d-ada2-9a0f3595c284_at_m17g2000prl.googlegroups.com>,
Bill Sloman wrote:


On Aug 31, 9:14 pm, John Fields <jfie...@austininstruments.com> wrote:

On Mon, 30 Aug 2010 18:58:11 -0700 (PDT), Bill Sloman

bill.slo...@ieee.org> wrote:

On Aug 31, 9:25 am, John Fields <jfie...@austininstruments.com> wrote:


SNIP to this point

One particularly cute application which passed through here a while
back was with someone who was looking to drive an audio transducer at
a higher level than could be afforded by a single transistor doing
Morse "H" forever, and someone suggested using a couple of 555's with
their totem poles arranged as a full bridge, thereby driving the
transducer with about about four times the power available from the
single transistor, at the same supply voltage.

I remember that he posted back, not quite awestruck, but certainly
quite impressed with the performance increase he enjoyed from his
transducer for certainly less than a dollar's worth of parts.

Another of the 101 things a boy can do with a 555.


A low cost 8-pin IC that can be used as an inverting buffer and that
can drive some dynamic loudspeakers can get a market by making very low
cost somewhat loud things that buzz or beep. Add a mere 4 capacitors
for "best practice", can often get away with 2, and if the transducer is a
piezo one fewer still, plus only one resistor.

Some of the things that boys and girls can do with a 555 can get a
market. My father told me that engineering is an economic science.
He even told me that it is not worth spending more than $999 on a pumpkin
cannon in a pumpkin cannon contest whose 1st prize is $1K, unless the
winning position has value beyond the prize payout.


----
And you can do what?
About three?

----
Only if I washed my hands afterwards.


I think that says something!!!

(Not that I usually agree with JF, who I find/"find" to often show mean
spirit.)


I doubt if this was
the only way of solving that poster's problem, and I'd be surprised if
it was the minimum solution, but since you haven't specified the
problem solved in any detail, this is pure speculation.

---

SNIP a bit of digression

There's enough detail there for someone skilled in the art to be able
to flesh out a solution.

We don't even have the rail voltage.


Most microprocessors simpler than a Pentium need voltages that a 555
can work from. So do most logic IC families.
If the supply voltage is a low one like 3.3 volts or less, then getting
a lot of sound from an audio transducer is likely to require a buffer,
voltage boost such as with a transformer (likely requiring a buffer after
digital type stuff), or trickery that gets harder to do if the
transducer's package has to be miniaturized, especially if the transducer
is a cheap one.
In such low voltage cases, I would try out a 556 and a 40106, and in
either case I feel like I am mildly abusing them. There is also the LM386
as a nice cheap 8-pin low-parts-count audio amplifier, somewhat optimized
towards lowish supply voltages like as low as 6 volts, works not much
worse at 4.5-5.

Bottom line, I like 555s because their cost is low, they are quick and
simple to implement, and they are *reliable* at doing many of the 101-plus
things that a child can do with them.


Of course that puts you at a disadvantage, so your only recourse is to
malign, instead of showing your minimalist "solution".
---

IIRR the 555's totem pole output doesn't get all that close to the
positive rail, so "four times the power available" may be something of
an exaggeration.

---
How so?

If the single transistor driving the load was a single 555's totem
pole emitter follower, then using two 555's in a full bridge, with the
same drop in each emitter follower, would result in about four times
the power dissipated in the load than in the case with a single 555.

Besides, what is it you don't understand about "about"?

With a single 555, the load can be returned directly to the postive
rail, and will see the rail voltage minus the saturation voltage of
the output - about 0.1V at 5mA.

With your "H" bridge, the load has to be connected between two totem
pole output stages. The low side will still be only about 0.1V above
the negative rail, but the high side will be around 1.4V below the
positive rail. With a 5V rail, you would not put four times as much
power into the load as the single-ended driver but only about twice as
much.


Using a single 555 to supply audio to an audio transducer, the 555
output typically alternately sources and sinks current through the load
and a coupling capacitor (with 2 exceptions). The peak-to-peak voltage
without these exceptions is still limited by how high the pull-up side of
the totem pole can up the output voltage to.
In that likely case, peak voltage across the transducer is close to
doubled by using 2 555s instead of one.

The exceptions are:

1: Add a pullup resistor from 555 output to B+ - with the extra power
consumption by the resistor.

2: The audio transducer conducts DC, and is connected from either the
output pin or the "discharge" pin to B+. That adds a power consumption
issue if power consumption matters or heat production in the transducer
matters, since that cause causes the transducer to dissipate DC power
(100% as heat, no sound) as well as AC power. Some loudspeakers don't
take DC well due to either extra heating and/or from their diaphragms
being constantly displaced in one direction from optimum position.
As for ehating - dynamic loudspeakers usually have DC resistance less than
their AC impedance at audio frequencies where they are useful.


http://focus.ti.com/lit/ds/symlink/ne555.pdf
You're bringing back memories of my younger years!

On Aug 31, 9:14 pm, John Fields <jfie...@austininstruments.com> wrote:
On Mon, 30 Aug 2010 18:58:11 -0700 (PDT), Bill Sloman

bill.slo...@ieee.org> wrote:
On Aug 31, 9:25 am, John Fields <jfie...@austininstruments.com> wrote:

One particularly cute application which passed through here a while
back was with someone who was looking to drive an audio transducer at
a higher level than could be afforded by a single transistor doing
Morse "H" forever, and someone suggested using a couple of 555's with
their totem poles arranged as a full bridge, thereby driving the
transducer with about about four times the power available from the
single transistor, at the same supply voltage.

I remember that he posted back, not quite awestruck, but certainly
quite impressed with the performance increase he enjoyed from his
transducer for certainly less than a dollar's worth of parts.

Another of the 101 things a boy can do with a 555.

----
And you can do what?
About three?
----
Only if I washed my hands afterwards.

I doubt if this was
the only way of solving that poster's problem, and I'd be surprised if
it was the minimum solution, but since you haven't specified the
problem solved in any detail, this is pure speculation.
---
SNIP a bit of digression

There's enough detail there for someone skilled in the art to be able
to flesh out a solution.

We don't even have the rail voltage.

Of course that puts you at a disadvantage, so your only recourse is to
malign, instead of showing your minimalist "solution".
---
IIRR the 555's totem pole output doesn't get all that close to the
positive rail, so "four times the power available" may be something of
an exaggeration.
---
How so?

If the single transistor driving the load was a single 555's totem
pole emitter follower, then using two 555's in a full bridge, with the
same drop in each emitter follower, would result in about four times
the power dissipated in the load than in the case with a single 555.

Besides, what is it you don't understand about "about"?

With a single 555, the load can be returned directly to the postive
rail, and will see the rail voltage minus the saturation voltage of
the output - about 0.1V at 5mA.

With your "H" bridge, the load has to be connected between two totem
pole output stages. The low side will still be only about 0.1V above
the negative rail, but the high side will be around 1.4V below the
positive rail. With a 5V rail, you would not put four times as much
power into the load as the single-ended driver but only about twice as
much.

http://focus.ti.com/lit/ds/symlink/ne555.pdf

And "about" implies variation above and below an estimate. Four times
the power is the upper limit to the advantage, available only with an
infinite supply voltage. You could have legitimately claimed an
advantage *approaching* a four-fold increase in power, but that sort
of careful use of language is quite beyond you.
--
Bill Sloman, Nijmegen
--

In <81685886-6c51-405d-ada2-9a0f3595c...@m17g2000prl.googlegroups.com>,

Bill Sloman wrote:
On Aug 31, 9:14 pm, John Fields <jfie...@austininstruments.com> wrote:
On Mon, 30 Aug 2010 18:58:11 -0700 (PDT), Bill Sloman

bill.slo...@ieee.org> wrote:
On Aug 31, 9:25 am, John Fields <jfie...@austininstruments.com> wrote:

SNIP to this point

One particularly cute application which passed through here a while
back was with someone who was looking to drive an audio transducer at
a higher level than could be afforded by a single transistor doing
Morse "H" forever, and someone suggested using a couple of 555's with
their totem poles arranged as a full bridge, thereby driving the
transducer with about about four times the power available from the
single transistor, at the same supply voltage.

I remember that he posted back, not quite awestruck, but certainly
quite impressed with the performance increase he enjoyed from his
transducer for certainly less than a dollar's worth of parts.

Another of the 101 things a boy can do with a 555.

  A low cost 8-pin IC that can be used as an inverting buffer and that
can drive some dynamic loudspeakers can get a market by making very low
cost somewhat loud things that buzz or beep.  Add a mere 4 capacitors
for "best practice", can often get away with 2, and if the transducer is a
piezo one fewer still, plus only one resistor.

  Some of the things that boys and girls can do with a 555 can get a
market.  My father told me that engineering is an economic science.
He even told me that it is not worth spending more than $999 on a pumpkin
cannon in a pumpkin cannon contest whose 1st prize is $1K, unless the
winning position has value beyond the prize payout.

----
And you can do what?
About three?
----
Only if I washed my hands afterwards.

  I think that says something!!!

  (Not that I usually agree with JF, who I find/"find" to often show mean
spirit.)

I doubt if this was
the only way of solving that poster's problem, and I'd be surprised if
it was the minimum solution, but since you haven't specified the
problem solved in any detail, this is pure speculation.
---

SNIP a bit of digression



There's enough detail there for someone skilled in the art to be able
to flesh out a solution.

We don't even have the rail voltage.

  Most microprocessors simpler than a Pentium need voltages that a 555
can work from.  So do most logic IC families.
  If the supply voltage is a low one like 3.3 volts or less, then getting
a lot of sound from an audio transducer is likely to require a buffer,
voltage boost such as with a transformer (likely requiring a buffer after
digital type stuff), or trickery that gets harder to do if the
transducer's package has to be miniaturized, especially if the transducer
is a cheap one.
  In such low voltage cases, I would try out a 556 and a 40106, and in
either case I feel like I am mildly abusing them.  There is also the LM386
as a nice cheap 8-pin low-parts-count audio amplifier, somewhat optimized
towards lowish supply voltages like as low as 6 volts, works not much
worse at 4.5-5.

" Bottom line, I like 555s because their cost is low, they are quick

Of course that puts you at a disadvantage, so your only recourse is to
malign, instead of showing your minimalist "solution".
---
IIRR the 555's totem pole output doesn't get all that close to the
positive rail, so "four times the power available" may be something of
an exaggeration.
---
How so?

If the single transistor driving the load was a single 555's totem
pole emitter follower, then using two 555's in a full bridge, with the
same drop in each emitter follower, would result in about four times
the power dissipated in the load than in the case with a single 555.

Besides, what is it you don't understand about "about"?

With a single 555, the load can be returned directly to the postive
rail, and will see the rail voltage minus the saturation voltage of
the output - about 0.1V at 5mA.

With your "H" bridge, the load has to be connected between two totem
pole output stages. The low side will still be only about 0.1V above
the negative rail, but the high side will be around 1.4V below the
positive rail. With a 5V rail, you would not put four times as much
power into the load as the single-ended driver but only about twice as
much.

  Using a single 555 to supply audio to an audio transducer, the 555
output typically alternately sources and sinks current through the load
and a coupling capacitor (with 2 exceptions).  The peak-to-peak voltage
without these exceptions is still limited by how high the pull-up side of
the totem pole can up the output voltage to.
  In that likely case, peak voltage across the transducer is close to
doubled by using 2 555s instead of one.

  The exceptions are:

1:  Add a pullup resistor from 555 output to B+ - with the extra power
consumption by the resistor.

2:  The audio transducer conducts DC, and is connected from either the
output pin or the "discharge" pin to B+.  That adds a power consumption
issue if power consumption matters or heat production in the transducer
matters, since that cause causes the transducer to dissipate DC power
(100% as heat, no sound) as well as AC power.  Some loudspeakers don't
take DC well due to either extra heating and/or from their diaphragms
being constantly displaced in one direction from optimum position.
As for ehating - dynamic loudspeakers usually have DC resistance less than
their AC impedance at audio frequencies where they are useful.

http://focus.ti.com/lit/ds/symlink/ne555.pdf

And "about" implies variation above and below an estimate. Four times
the power is the upper limit to the advantage, available only with an
infinite supply voltage. You could have legitimately claimed an
advantage *approaching* a four-fold increase in power, but that sort
of careful use of language is quite beyond you.
--
Bill Sloman, Nijmegen

--
 - Don Klipstein (d...@misty.com)

Bill Sloman wrote:
On Aug 30, 5:07 am, ehsjr <eh...@nospamverizon.net> wrote:

BillSlomanwrote:

snip

That is the wording that that you would have preferred that I used.
Everybody's opinion of the reliability of their knowledge is
fundamentally subjective, but my data-base has been being tested
against reality for some fifty years now, and has proved to be pretty
reliable.

You seem to have stopped testing yours against reality around the time
the 555 became obsolescent, which would be about thirty years ago.

Hmmm.  A search in Mouser for the 555 yields 6 pages. On the
first page alone you'll find that there are 152,667 555s in
stock. Searching for 555s in Digikey yields 4 pages of results,
all in stock.  The quantity on the first page alone totally
swamps the Mouser quantities - well over 400,000 in stock.

Mouser and Digikey (and others) seem to have a better grip on
reality than you do, focusing on the viability of the part,
rather than what you see as its "obsolence".

The 555 is a legacy part - like the the 741 - and still sells in large
numbers. When the 555 was introduced it did provide a compact and
adequate solution to a commonly encountered problem, and was designed
into a lot of products. Some of these are still in production.

As with all frequently used parts, it is still beoing incoprporated
into new designs. Hobbyists and amateurs copy old designs, because
they know - or at least fondly believe - that they work, and don't
know enough to design anything better.

Some professional designers - like John Fields - who should know
better, still design around legacy parts, because it lets them recycle
old designs which they know to be reliable. If you are designing
something in a hurry, or don't want to risk designing something that
you can't be sure will work out of the box, using familiar - if
obsolete - parts can be a good short term strategy.

The catch with the 555 is that it combines a part nobody really ought
to use these days - a monostable - with a rather poor quality bipolar
power transistor, and uses the same ground return pin for both
devices. There are a few situations where these defects aren't
troublesome, but modern designers tend to make their time control
signals in the digital domain, and use then to drive a MOSFET switch.

--
Bill Sloman, Nijmegen

Thank you for giving a reasoned reply. I would like to ask about one
part of it: "The catch with the 555 is that it combines a part nobody
really ought to use these days - a monostable - with a rather poor
quality bipolar power transistor, and uses the same ground return pin
for both devices."

I do not understand why you make a blanket statement indicating
that one should not use a monostable.  If a monostable does the
job, why use something else?  

If you've got a money making idea that requires
nothing more than a 555, would you reject it because it contains
a monostable?  Would you insist on something other than the 555?