FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Electronix » design
Flag desecration?
Post new topic   Reply to topic Page 14 of 16 [227 Posts] View previous topic :: View next topic
Goto page:  Previous  1, 2, 3, ..., 12, 13, 14, 15, 16 Next
Author Message
John Fields
electronics forum Guru


Joined: 24 Mar 2005
Posts: 3260

PostPosted: Tue Jul 18, 2006 12:59 am    Post subject: Re: Flag desecration? Reply with quote

On 17 Jul 2006 10:53:59 -0700, bill.sloman@ieee.org wrote:

Quote:

John Fields wrote:
On 16 Jul 2006 16:29:33 -0700, bill.sloman@ieee.org wrote:


Since I do understand the equations, I can tell you that fiddling with
the high and low output voltages doesn't make any significant
difference to the proposition that building monstables with TTL gates
is a mug's game, and I'm certainly not interested in spending any more
time educating you in this relatively trivial aspect of circuit
analysis, which is another mug's game.

---
Since you don't seem to be able to comprehend the difference between
charging and discharging and are totally incapable of understanding
the graphics I presented to help you along,

s**t. I blew it.

---
Welcome to the Human race Smile
---

Quote:
Okay. So that worst case is 0.133 time constants. Actually

ln(3.6 -0.4)/(3.6 -0.Cool= 0.13353

---
Yup.
---

Quote:
My (defensible) assumption of a slightly higher worst case output
voltage of 3.8V
gives

ln (3.8-04)/3.8-0.Cool = 0.125

---
Your defense depends on proving that the Vce drop in the top
totem-pole emitter follower NPN will average out to 0.6V and the Vf
of the diode in series with its emitter will also average out to
0.6V over the range of currents we'll encounter while charging the
cap.

Do you want to go there?
---

Quote:
The other extreme on charging up is charging up from 0V - okay for you
0.1V - towards 2.4V, with the threshold at 2.0V, which takes 1.75 time
constants.

but 1.75/0.133 = 13.15

---
Congratulations! You finally got it right.
---

Quote:
and there is still more than 10:1 tolerance on the delay for a given RC
product.

---
Perhaps "variation" is a better choice of word, but it's even worse
than that if you consider the tolerances of the timing components.
---

Quote:
Designing monstables around TTL gates is still a mugs game.

---
Sure, now that you know how to do it it is, and now you know what
rheostats are for. ;)

BTW, I've posted some graphics to abse you might find interesting.


--
John Fields
Professional Circuit Designer
Back to top
Bill Sloman
electronics forum Guru


Joined: 12 May 2005
Posts: 1080

PostPosted: Tue Jul 18, 2006 10:47 am    Post subject: Re: Flag desecration? Reply with quote

Frank Bemelman wrote:
Quote:
bill.sloman@ieee.org> schreef in bericht
news:1153158839.138189.8680@b28g2000cwb.googlegroups.com...

and there is still more than 10:1 tolerance on the delay for a given RC
product.

Should that not be ~10% or 10:11 or something.

No. Try and make a monostable with a simple TTL gate and the delay you
actually get can vary from something like twice the RC product to less
than 20% of the RC product.

There are situations where this is acceptable, but you end up having to
be sure that you can cope with a delay more than ten times longer than
you need in order to be sure of generating the minimum delay you can
get away with.

--
Bill Sloman, Nijmegen
Back to top
Bill Sloman
electronics forum Guru


Joined: 12 May 2005
Posts: 1080

PostPosted: Tue Jul 18, 2006 11:09 am    Post subject: Re: Flag desecration? Reply with quote

John Fields wrote:
Quote:
On 17 Jul 2006 10:53:59 -0700, bill.sloman@ieee.org wrote:


John Fields wrote:
On 16 Jul 2006 16:29:33 -0700, bill.sloman@ieee.org wrote:


Since I do understand the equations, I can tell you that fiddling with
the high and low output voltages doesn't make any significant
difference to the proposition that building monstables with TTL gates
is a mug's game, and I'm certainly not interested in spending any more
time educating you in this relatively trivial aspect of circuit
analysis, which is another mug's game.

---
Since you don't seem to be able to comprehend the difference between
charging and discharging and are totally incapable of understanding
the graphics I presented to help you along,

s**t. I blew it.

---
Welcome to the Human race Smile
---

Okay. So that worst case is 0.133 time constants. Actually

ln(3.6 -0.4)/(3.6 -0.Cool= 0.13353

---
Yup.
---

My (defensible) assumption of a slightly higher worst case output
voltage of 3.8V
gives

ln (3.8-04)/3.8-0.Cool = 0.125

---
Your defense depends on proving that the Vce drop in the top
totem-pole emitter follower NPN will average out to 0.6V and the Vf
of the diode in series with its emitter will also average out to
0.6V over the range of currents we'll encounter while charging the
cap.

Do you want to go there?
---

No. Which is why I prefer to assume the worst possilbe case - of zero
voltage drop across both diodes, unrealistic as it is. Vbe is
proportional to the log of the current density in the diode divided by
the "off" leakage current which we don't really know.

In the event it doesn't make much difference.

Quote:
The other extreme on charging up is charging up from 0V - okay for you
0.1V - towards 2.4V, with the threshold at 2.0V, which takes 1.75 time
constants.

but 1.75/0.133 = 13.15

---
Congratulations! You finally got it right.
---

I've had it roughly right all along - 10:1 was my original claim and
worst than 10:1 iss what we come out with.

Quote:
and there is still more than 10:1 tolerance on the delay for a given RC
product.

---
Perhaps "variation" is a better choice of word, but it's even worse
than that if you consider the tolerances of the timing components.
---

Agreed. You can buy 1% polypropylene film capacitors and 0.1%
resistors, but you wouldn't bother in this sort of application.

Quote:
Designing monstables around TTL gates is still a mugs game.

---
Sure, now that you know how to do it it is, and now you know what
rheostats are for. Wink

Rheostats aka potentiometers are devices which are adjusted by service
engineers and graduate students until the circuit stops working, so
they can get to meet a real engineer and learn things about their
ancestry that their mother never told them.

Quote:
BTW, I've posted some graphics to abse you might find interesting.

You've got LTSpice; why not use it to make decent graphics?

--
Bill Sloman, Nijmegen
Back to top
John Fields
electronics forum Guru


Joined: 24 Mar 2005
Posts: 3260

PostPosted: Tue Jul 18, 2006 1:19 pm    Post subject: Re: Flag desecration? Reply with quote

On 18 Jul 2006 04:09:04 -0700, bill.sloman@ieee.org wrote:

Quote:
Rheostats aka potentiometers

---
In error.

A rheostat is a two-terminal device, while a potentiometer is a
three-terminal device.

Both are variable resistors and a potentiometer can be _used_ as a
rheostat, but that doesn't make it one.
---

Quote:
are devices which are adjusted by service
engineers and graduate students until the circuit stops working, so
they can get to meet a real engineer and learn things about their
ancestry that their mother never told them.

BTW, I've posted some graphics to abse you might find interesting.

You've got LTSpice; why not use it to make decent graphics?

--
Why bother?

What I posted was good enough. Was it illegible?


--
John Fields
Professional Circuit Designer
Back to top
Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Tue Jul 18, 2006 1:22 pm    Post subject: Re: Flag desecration? Reply with quote

bill.sloman@ieee.org wrote:
Quote:



Rheostats aka potentiometers


Where would that be? Between your ears? A Rheostat has two
terminals, a Potentiometer has three.. How do you set a "Potential" on
a two terminal device that can only be adjusted from 0 Ohms, to its
maximum value. Its a whole nother animal, Willie.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Back to top
Bill Sloman
electronics forum Guru


Joined: 12 May 2005
Posts: 1080

PostPosted: Wed Jul 19, 2006 3:00 am    Post subject: Re: Flag desecration? Reply with quote

Michael A. Terrell wrote:
Quote:
bill.sloman@ieee.org wrote:



Rheostats aka potentiometers


Where would that be? Between your ears? A Rheostat has two
terminals, a Potentiometer has three.. How do you set a "Potential" on
a two terminal device that can only be adjusted from 0 Ohms, to its
maximum value. Its a whole nother animal, Willie.

And how do you make a rheostat so that it isn't a potential
potentiometer?
Leave off the third terminal?

Admittedly, a purpose-designed rheostat will be able to take a lot more
current through the wiper than a purpose designed potentiometer, but in
the context of John Fields' remark, which had to apply to printed
circuit mounted twiddle pots, the difference is academic.

Grow up ...

--
Bill Sloman, Nijmegen
Back to top
Phat Bytestard
electronics forum beginner


Joined: 15 Jul 2006
Posts: 49

PostPosted: Wed Jul 19, 2006 3:05 am    Post subject: Re: Flag desecration? Reply with quote

On 18 Jul 2006 20:00:28 -0700, bill.sloman@ieee.org Gave us:

Quote:

Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:



Rheostats aka potentiometers


Where would that be? Between your ears? A Rheostat has two
terminals, a Potentiometer has three.. How do you set a "Potential" on
a two terminal device that can only be adjusted from 0 Ohms, to its
maximum value. Its a whole nother animal, Willie.

And how do you make a rheostat so that it isn't a potential
potentiometer?
Leave off the third terminal?

Admittedly, a purpose-designed rheostat will be able to take a lot more
current through the wiper than a purpose designed potentiometer, but in
the context of John Fields' remark, which had to apply to printed
circuit mounted twiddle pots, the difference is academic.

Grow up ...

You grow up. Most potentiometers (even the high precision wirewound
jobs) are sub-watt devices.

Most rheostats are multi-watt devices.

Got clue? It isn't about configuration, it IS about purpose.
Back to top
Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Wed Jul 19, 2006 5:27 am    Post subject: Re: Flag desecration? Reply with quote

Phat Bytestard wrote:
Quote:

On 18 Jul 2006 20:00:28 -0700, bill.sloman@ieee.org Gave us:


Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:



Rheostats aka potentiometers


Where would that be? Between your ears? A Rheostat has two
terminals, a Potentiometer has three.. How do you set a "Potential" on
a two terminal device that can only be adjusted from 0 Ohms, to its
maximum value. Its a whole nother animal, Willie.

And how do you make a rheostat so that it isn't a potential
potentiometer?
Leave off the third terminal?

Admittedly, a purpose-designed rheostat will be able to take a lot more
current through the wiper than a purpose designed potentiometer, but in
the context of John Fields' remark, which had to apply to printed
circuit mounted twiddle pots, the difference is academic.

Grow up ...

You grow up. Most potentiometers (even the high precision wirewound
jobs) are sub-watt devices.

Most rheostats are multi-watt devices.

Got clue? It isn't about configuration, it IS about purpose.


Forget it. Bill is so brainwashed that he thinks he's right. It
doesn't matter if every textbook and datasheet shows them properly,
he'll insist that he's right. :(


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Back to top
Eeyore
electronics forum Guru


Joined: 22 Jun 2006
Posts: 642

PostPosted: Wed Jul 19, 2006 6:27 am    Post subject: Re: Flag desecration? Reply with quote

"Michael A. Terrell" wrote:

Quote:
Forget it. Bill is so brainwashed that he thinks he's right.

Duh ! The only one brainwashed round here is clearly you, who thinks that the
USA is beyond even reproach !

Graham
Back to top
Phat Bytestard
electronics forum beginner


Joined: 15 Jul 2006
Posts: 49

PostPosted: Wed Jul 19, 2006 7:59 am    Post subject: Re: Flag desecration? Reply with quote

On Wed, 19 Jul 2006 07:27:52 +0100, Eeyore
<rabbitsfriendsandrelations@REMOVETHIS.hotmail.com> Gave us:

Quote:


"Michael A. Terrell" wrote:

Forget it. Bill is so brainwashed that he thinks he's right.

Duh ! The only one brainwashed round here is clearly you, who thinks that the
USA is beyond even reproach !

Pullin' back some of those layers, and showing us some onion, eh?
Back to top
Bill Sloman
electronics forum Guru


Joined: 12 May 2005
Posts: 1080

PostPosted: Wed Jul 19, 2006 9:37 am    Post subject: Re: Flag desecration? Reply with quote

Phat Bytestard wrote:
Quote:
On 18 Jul 2006 20:00:28 -0700, bill.sloman@ieee.org Gave us:


Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:



Rheostats aka potentiometers


Where would that be? Between your ears? A Rheostat has two
terminals, a Potentiometer has three.. How do you set a "Potential" on
a two terminal device that can only be adjusted from 0 Ohms, to its
maximum value. Its a whole nother animal, Willie.

And how do you make a rheostat so that it isn't a potential
potentiometer?
Leave off the third terminal?

Admittedly, a purpose-designed rheostat will be able to take a lot more
current through the wiper than a purpose designed potentiometer, but in
the context of John Fields' remark, which had to apply to printed
circuit mounted twiddle pots, the difference is academic.

Grow up ...

You grow up. Most potentiometers (even the high precision wirewound
jobs) are sub-watt devices.

Most rheostats are multi-watt devices.

Got clue? It isn't about configuration, it IS about purpose.

Get a clue yourself - the sort of rheostat you use to control the
precise time delay generate by a monostable (which is what John Fields
was tallong about) isn't a multiwatt device, and the difference between
a 2-terminal rheostat and a 3-terminal potentiometer *is* essentially
configuration. John was being pedantic - but correct - when he used the
term rheostat for what everybody else calls a twiddle pot.

The word rheostat, coined in 1843 by English physicist Sir Charles
Wheatstone (1802-75) comes from the Greek. rheos "a flowing, stream"
(from PIE base *sreu-, see rheum) + -stat "regulating device" and
doesn't have any implied wattage.

--
Bill Sloman, Nijmegen
Back to top
Bill Sloman
electronics forum Guru


Joined: 12 May 2005
Posts: 1080

PostPosted: Wed Jul 19, 2006 10:02 am    Post subject: Re: Flag desecration? Reply with quote

Michael A. Terrell wrote:
Quote:
Phat Bytestard wrote:

On 18 Jul 2006 20:00:28 -0700, bill.sloman@ieee.org Gave us:


Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:



Rheostats aka potentiometers


Where would that be? Between your ears? A Rheostat has two
terminals, a Potentiometer has three.. How do you set a "Potential" on
a two terminal device that can only be adjusted from 0 Ohms, to its
maximum value. Its a whole nother animal, Willie.

And how do you make a rheostat so that it isn't a potential
potentiometer?
Leave off the third terminal?

Admittedly, a purpose-designed rheostat will be able to take a lot more
current through the wiper than a purpose designed potentiometer, but in
the context of John Fields' remark, which had to apply to printed
circuit mounted twiddle pots, the difference is academic.

Grow up ...

You grow up. Most potentiometers (even the high precision wirewound
jobs) are sub-watt devices.

Most rheostats are multi-watt devices.

Got clue? It isn't about configuration, it IS about purpose.


Forget it. Bill is so brainwashed that he thinks he's right. It
doesn't matter if every textbook and datasheet shows them properly,
he'll insist that he's right. Sad

Huh? What John Fields has pedantically and properly called rheostats
are - in the context discussed - merely potentiometers with one
connection either ignored or shorted to the wiper. Most people call
them twiddle pots.

Where are the textbooks you fondly hope will show that I'm wrong in
this contention?

And why encourage me towards the delusion that I'm always right by
putting up such a lame counter-argument?

--
Bill Sloman, Nijmegen
Back to top
John Fields
electronics forum Guru


Joined: 24 Mar 2005
Posts: 3260

PostPosted: Wed Jul 19, 2006 1:09 pm    Post subject: Re: Flag desecration? Reply with quote

On 18 Jul 2006 20:00:28 -0700, bill.sloman@ieee.org wrote:

Quote:

Michael A. Terrell wrote:
bill.sloman@ieee.org wrote:



Rheostats aka potentiometers


Where would that be? Between your ears? A Rheostat has two
terminals, a Potentiometer has three.. How do you set a "Potential" on
a two terminal device that can only be adjusted from 0 Ohms, to its
maximum value. Its a whole nother animal, Willie.

And how do you make a rheostat so that it isn't a potential
potentiometer?
Leave off the third terminal?

Admittedly, a purpose-designed rheostat will be able to take a lot more
current through the wiper than a purpose designed potentiometer, but in
the context of John Fields' remark, which had to apply to printed
circuit mounted twiddle pots, the difference is academic.

---
As was the discussion, almost, so calling things what they are
should have been de rigueur.
---

Quote:
Grow up ...

---
Blow up.


--
John Fields
Professional Circuit Designer
Back to top
Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Wed Jul 19, 2006 3:23 pm    Post subject: Re: Flag desecration? Reply with quote

bill.sloman@ieee.org wrote:
Quote:

Huh? What John Fields has pedantically and properly called rheostats
are - in the context discussed - merely potentiometers with one
connection either ignored or shorted to the wiper. Most people call
them twiddle pots.

Where are the textbooks you fondly hope will show that I'm wrong in
this contention?

And why encourage me towards the delusion that I'm always right by
putting up such a lame counter-argument?

--
Bill Sloman, Nijmegen


By definition a two terminal variable resistor is a Rheostat. A
Three terminal variable resistor is a Potentiometer. Id doesn't matter
whether you use two or three terminals. Yes, you can use it as a
rheostat, but it is still a Potentiometer. The application of a
component doesn't change what it is. Using an inductor, a capacitor,
or even a diode to reduce the current flow in a circuit doesn't make it
a resistor.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Back to top
Phat Bytestard
electronics forum beginner


Joined: 15 Jul 2006
Posts: 49

PostPosted: Thu Jul 20, 2006 2:42 am    Post subject: Re: Flag desecration? Reply with quote

On 19 Jul 2006 02:37:02 -0700, bill.sloman@ieee.org Gave us:

Quote:
Get a clue yourself - the sort of rheostat you use to control the
precise time delay generate by a monostable (which is what John Fields
was tallong about) isn't a multiwatt device, and the difference between
a 2-terminal rheostat and a 3-terminal potentiometer *is* essentially
configuration. John was being pedantic - but correct - when he used the
term rheostat for what everybody else calls a twiddle pot.


All one has to do is clamp one end leg to the wiper, dumbass. It is,
at that point, a "VR" or "variable resistor". A rheostat is typically
used to regulate current. LARGE amounts of current. A variable
resistor regulates small amounts of current. I would never call a VR
that I incorporated into a low power circuit a "rheostat", even though
the effect that takes place in such a configuration is defined as
"rheostatic".

It is really personal preference. Just as some call an inductor a
"choke" based on the application they have utilized the device in.
Back to top
Google

Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 14 of 16 [227 Posts] Goto page:  Previous  1, 2, 3, ..., 12, 13, 14, 15, 16 Next
View previous topic :: View next topic
The time now is Sat Jun 24, 2017 1:45 am | All times are GMT
Forum index » Electronix » design
Jump to:  


Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums |  Medicine forum |  Science forum  |  Send and track newsletters


Powered by phpBB © 2001, 2005 phpBB Group