Transistor as a current limiter

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:q4ast8pu4ke6jpihq69cicjdem6j95ir4o@4ax.com...
On Wed, 10 Jul 2013 21:33:08 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:

snip
Having read some of the suggestions, I notice very few of the minimalist
solutions I favour.

The minimalist 1 transistor current source: give the transistor a fixed
base
bias (like the Vf of a LED) and ground the emitter via a resistance (the
value of which determines collector current). If current tries to
increase;
the voltage on the emitter resistor creeps upward and cancels some of the
fixed base bias - which acts to regulate the current.

Its that simple.

I think that was already in the OP's original, very first
post... along with some comments from the OP in that same
post that showed thinking going on about it.
Click to expand...
Reviewing the OP's posts to date, I notice 32 chains are intended - the
single transistor current source doesn't have to be repeated 32 times - just
use a 32 element current mirror.
 
On Thu, 11 Jul 2013 17:49:22 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:q4ast8pu4ke6jpihq69cicjdem6j95ir4o@4ax.com...
On Wed, 10 Jul 2013 21:33:08 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:

snip
Having read some of the suggestions, I notice very few of the minimalist
solutions I favour.

The minimalist 1 transistor current source: give the transistor a fixed
base
bias (like the Vf of a LED) and ground the emitter via a resistance (the
value of which determines collector current). If current tries to
increase;
the voltage on the emitter resistor creeps upward and cancels some of the
fixed base bias - which acts to regulate the current.

Its that simple.

I think that was already in the OP's original, very first
post... along with some comments from the OP in that same
post that showed thinking going on about it.

Reviewing the OP's posts to date, I notice 32 chains are intended - the
single transistor current source doesn't have to be repeated 32 times - just
use a 32 element current mirror.
Click to expand...
That's been discussed.

Jon
 
On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from JT -
even JF is having trouble finding people to rag on!
Click to expand...
Oh... well.... Then I will most certainly be dead before I
could use up a 1Tb purchase.

Jon
 
"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:2d3ut85op5ucflgnv7rice8oo4ehrinbr0@4ax.com...
On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from JT -
even JF is having trouble finding people to rag on!

Oh... well.... Then I will most certainly be dead before I
could use up a 1Tb purchase.
Click to expand...
Over the years I've downloaded at least 1Tb from
alt.binaries.e-book.technical

Very likely I'll be dead before I can read that many books & magazines.
 
On Thu, 11 Jul 2013 21:05:10 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:2d3ut85op5ucflgnv7rice8oo4ehrinbr0@4ax.com...
On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from JT -
even JF is having trouble finding people to rag on!

Oh... well.... Then I will most certainly be dead before I
could use up a 1Tb purchase.

Over the years I've downloaded at least 1Tb from
alt.binaries.e-book.technical

Very likely I'll be dead before I can read that many books & magazines.
Click to expand...
Hmm. Haven't looked at that one. And yes, it looks like one
way or another I'll be dead (and still have more capacity to
download.)

By the way, I did get the list of currently suppported groups
at astraweb located at:

http://www.news.astraweb.com/active.html

For anyone else wondering like I was.

No information at all on how long they retain things, though.

Jon
 
On Wed, 10 Jul 2013 08:17:10 +0000 (UTC), Lauri Alanko <la@iki.fi>
wrote:

In article <k81pt8hv7o0bjbsn6sn577bhihcelgkmb7@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
On Tue, 9 Jul 2013 18:43:28 +0000 (UTC), Lauri Alanko <la@iki.fi
wrote:
I don't even know which leds I'm going to use yet.

---
Then you've wasted our time by asking for help by stating that they'll
drop 2.2V?

I'm sorry if I gave that impression. I merely gave an example
calculation, with realistic sample values, to demonstrate my concern
with the circuit in question. I hoped to emphasize that this was
merely hypothetical by using words such as "suppose", "load would be",
"if we designed" etc.
Click to expand...
---
When you originally stated that you were using a 12V supply and that
the LED Vf was 2.2V, I - quite naturally, I think - assumed that
that's what you were working with.

As a consequence, I posted a circuit which would give you the
current-limiting and PWM capabilities you were looking for.
---

Besides, in the same example the supply voltage was 12 V, and that
didn't prevent you from suggesting otherwise. Surely there was nothing
to prevent you from suggesting different leds, as well?
Click to expand...
---
Had I known earlier that your LED choices weren't carved in stone and
that you were looking for something fairly wide-angle, I might have.

As for the power supply, I felt compelled to show you that a higher
voltage would allow you to run a longer series string of LEDs for less
money spent on hardware, and higher efficiency to boot.
---

In any case, I don't see how anyone's time has been wasted.
Click to expand...
---
I forgot that this is sci.electronics.basics, so you're right, of
course, and I apologize for being snarky.
---

All the
replies I've received have been most pertinent and educational, and
the circuits I've seen seem useful regardless of whether one plugs in
four 2.2 V leds or three 3.6 V leds per series.
Click to expand...
---
Indeed, and my entries were intended to illustrate how you could use a
simple, inexpensive single-transistor common emitter circuit to
achieve your stated goals.

But, with no feedback until now, it was impossible to determine
whether or not _my_ time was wasted in trying to help you.

As it turns out, it wasn't, because any of the circuits I posted can
be scaled up, using a higher driving voltage and longer LED strings,
to get you the most efficient and inexpensive use of your resources.


--
JF
 
On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from JT -
even JF is having trouble finding people to rag on!
Click to expand...
---
Au contraire. I've just been on an asshole-free sabbatical.

Had I not been, I would have taken exception to the latest of your
idiotic posts on abse where you demonstrated your moronosity by
stating:

"SiC rectifiers are supposed to be all the rage, but I've heard they
have a large Vf, and I've no idea how much junction capacitance."

Perusing a data sheet in order to glean that sort of data would seem
to be de rigueur for someone interested in the art.

But you?

Sounds to me like you're the one who's got the rag on.

--
JF
 
On Thu, 11 Jul 2013 21:05:10 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:2d3ut85op5ucflgnv7rice8oo4ehrinbr0@4ax.com...
On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from JT -
even JF is having trouble finding people to rag on!

Oh... well.... Then I will most certainly be dead before I
could use up a 1Tb purchase.

Over the years I've downloaded at least 1Tb from
alt.binaries.e-book.technical
Click to expand...
---
To what avail?
---

Very likely I'll be dead before I can read that many books & magazines.
Click to expand...
---
Your mother should have taught you about your eyes being bigger than
your stomach.

--
JF
 
On Thu, 11 Jul 2013 16:32:02 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from JT -
even JF is having trouble finding people to rag on!

---
Au contraire. I've just been on an asshole-free sabbatical.

Had I not been, I would have taken exception to the latest of your
idiotic posts on abse where you demonstrated your moronosity by
stating:

"SiC rectifiers are supposed to be all the rage, but I've heard they
have a large Vf, and I've no idea how much junction capacitance."

Perusing a data sheet in order to glean that sort of data would seem
to be de rigueur for someone interested in the art.

But you?

Sounds to me like you're the one who's got the rag on.
Click to expand...
Damn! I had forgotten Ian Field even existed >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)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.
 
In article <oq5ut8ddooi9f0g0gf3bhcm7gut535btvh@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
All the
replies I've received have been most pertinent and educational, and
the circuits I've seen seem useful regardless of whether one plugs in
four 2.2 V leds or three 3.6 V leds per series.

---
Indeed, and my entries were intended to illustrate how you could use a
simple, inexpensive single-transistor common emitter circuit to
achieve your stated goals.

But, with no feedback until now, it was impossible to determine
whether or not _my_ time was wasted in trying to help you.
Click to expand...
Sorry for not responding to your posts earlier. I was a bit
overwhelmed by the number of replies to what seemed to be a relatively
straightforward query. After the current mirror circuit, which seemed
ideal, the point of the additional suggestions seemed lost to me,
especially since there was no explication of how they would be
superior.

You are suggesting using a resistor as a current limiter, and a
transistor as an on/off switch for PWM. This doesn't seem ideal to me.
Firstly, it requires multiple components per chain (though there is an
obvious variant where there is a single power transistor switching the
supply to all the chains). But more importantly, a resistor is a
fragile current limiter: the current will depend on fluctuations in the
supply voltage and the I-V curves of the leds (which, I hear, are
prone to individual variations). And if a single led shorts, the
current to the others will increase, decreasing their lifetime as
well. I doubt these issues will be very relevant for my toy project,
but I want to learn to do things properly.

The reason I asked about using a _transistor_ as a current limiter is
that transistors are mostly immune to such fluctuations at the
collector, and only their (relatively low) base voltage needs to be
well-regulated. This seems superior to using a resistor, and there is
the added advantage that the same transistor can also be controlled to
provide e.g. PWM.

However, I recently learned that PWM is not actually very efficient
with leds: it seems that leds provide more light per watt when run at
constant low currents than when pulsed at a high current. PWM, though,
provides better linearity and stable color. But even if I want to use
adjustable current instead of PWM, the current mirror still works:
just attach a voltage-controlled current source to the mirror. So I
think I'm going to stick with that one.

But thanks for your suggestions, regardless.


Lauri
 
"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
message news:41out8l1irdc2hjacod8jf9pejpcduo03o@4ax.com...
On Thu, 11 Jul 2013 16:32:02 -0500, John Fields
jfields@austininstruments.com> wrote:

On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from
JT -
even JF is having trouble finding people to rag on!

---
Au contraire. I've just been on an asshole-free sabbatical.

Had I not been, I would have taken exception to the latest of your
idiotic posts on abse where you demonstrated your moronosity by
stating:

"SiC rectifiers are supposed to be all the rage, but I've heard they
have a large Vf, and I've no idea how much junction capacitance."

Perusing a data sheet in order to glean that sort of data would seem
to be de rigueur for someone interested in the art.

But you?

Sounds to me like you're the one who's got the rag on.

Damn! I had forgotten Ian Field even existed >:-}
Click to expand...
Trust JF to stir things up!
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:3nbut8dum6os61c47h7t7sdpuftrofsipa@4ax.com...
On Thu, 11 Jul 2013 21:05:10 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:2d3ut85op5ucflgnv7rice8oo4ehrinbr0@4ax.com...
On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from
JT -
even JF is having trouble finding people to rag on!

Oh... well.... Then I will most certainly be dead before I
could use up a 1Tb purchase.

Over the years I've downloaded at least 1Tb from
alt.binaries.e-book.technical

---
To what avail?
Click to expand...
Knowing what a shit stirrer you are, I'm in no great hurry to provide you
with ammunition.
 
On Fri, 12 Jul 2013 14:06:37 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
message news:41out8l1irdc2hjacod8jf9pejpcduo03o@4ax.com...
On Thu, 11 Jul 2013 16:32:02 -0500, John Fields
jfields@austininstruments.com> wrote:

On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from
JT -
even JF is having trouble finding people to rag on!

---
Au contraire. I've just been on an asshole-free sabbatical.

Had I not been, I would have taken exception to the latest of your
idiotic posts on abse where you demonstrated your moronosity by
stating:

"SiC rectifiers are supposed to be all the rage, but I've heard they
have a large Vf, and I've no idea how much junction capacitance."

Perusing a data sheet in order to glean that sort of data would seem
to be de rigueur for someone interested in the art.

But you?

Sounds to me like you're the one who's got the rag on.

Damn! I had forgotten Ian Field even existed >:-}

Trust JF to stir things up!
Click to expand...
---
Everything was nice and cordial until you showed up and started
flaming for no reason at all but to throw some shit into the game.

You're a mean, reprehensible person who's only goal is to toot his own
horn no matter what the cost.

--
JF
 
On Fri, 12 Jul 2013 14:56:01 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:3nbut8dum6os61c47h7t7sdpuftrofsipa@4ax.com...
On Thu, 11 Jul 2013 21:05:10 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:2d3ut85op5ucflgnv7rice8oo4ehrinbr0@4ax.com...
On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from
JT -
even JF is having trouble finding people to rag on!

Oh... well.... Then I will most certainly be dead before I
could use up a 1Tb purchase.

Over the years I've downloaded at least 1Tb from
alt.binaries.e-book.technical

---
To what avail?

Knowing what a shit stirrer you are, I'm in no great hurry to provide you
with ammunition.
Click to expand...
---
Then just shut the fuck up altogether.


--
JF
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:up50u8timu504keruokdg9ind337kkd5di@4ax.com...
On Fri, 12 Jul 2013 14:06:37 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote
in
message news:41out8l1irdc2hjacod8jf9pejpcduo03o@4ax.com...
On Thu, 11 Jul 2013 16:32:02 -0500, John Fields
jfields@austininstruments.com> wrote:

On Thu, 11 Jul 2013 15:20:21 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Jon Kirwan" <jonk@infinitefactors.org> wrote in message
news:jiost81cvb7ll2s60iorlhfbum1blg9k6b@4ax.com...
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

On 2013-07-10, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Wed, 10 Jul 2013 12:34:35 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:


"Jon Kirwan" <jonk@infinitefactors.org> schreef in bericht
news:smhjt8tn6rjs61esale74fo2d0ikknc1gm@4ax.com...
On Sun, 7 Jul 2013 15:17:59 +0200, "petrus bitbyter"
petrus.bitbyter@hotmail.com> wrote:

snip
Suppose Q2 slipped through non reversed?

I actually caught that mistake, right away. Note my
self-reply shortly after?

Missed it completely. That's to say my newsserver did. Now you
mentioned
it,
I found it in Google groups.

Thanks for the note about it. Yeah, I get it. Nice you caught
it, too. I might have missed it myself and that's a good
catch from you!

After my internet service (Verizon) decided to remove from
their contract, unilaterally and without my permission of
course, NNTP services... I pretty much was forced to "go find
something." I'm paying 10 euros (despite being in the US) per
year for a service offered in Europe and it appears to be
working well these last years (fast.) news.individual.net.

Seems to get everything I care about, perhaps except for
alt.binaries.schematics.electronic. I have to just live with
that for now.

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic?

ABSE is pretty much a dead group with occasional political rants from
JT -
even JF is having trouble finding people to rag on!

---
Au contraire. I've just been on an asshole-free sabbatical.

Had I not been, I would have taken exception to the latest of your
idiotic posts on abse where you demonstrated your moronosity by
stating:

"SiC rectifiers are supposed to be all the rage, but I've heard they
have a large Vf, and I've no idea how much junction capacitance."

Perusing a data sheet in order to glean that sort of data would seem
to be de rigueur for someone interested in the art.

But you?

Sounds to me like you're the one who's got the rag on.

Damn! I had forgotten Ian Field even existed >:-}

Trust JF to stir things up!

---
Everything was nice and cordial until you showed up and started
flaming for no reason at all but to throw some shit into the game.

You're a mean, reprehensible person who's only goal is to toot his own
horn no matter what the cost.
Click to expand...
Run along now - it must be time for your hourly crack pipe.
 
On Fri, 12 Jul 2013 09:54:58 +0000 (UTC), Lauri Alanko
<la@iki.fi> wrote:

snip
However, I recently learned that PWM is not actually very efficient
with leds: it seems that leds provide more light per watt when run at
constant low currents than when pulsed at a high current.
Click to expand...
Your statement here needs clarification. It's not as nuanced
as it probably should be.

PWM is simply a method of using a duty cycle (from 0% to
100%) to adjust the apparent intensity. It is not necessarily
the case that it is less efficient with LEDs. It may be. But
not necessarily.

Let's say you are using PWM to adjust the brightness of a
single LED. Normally, at 100% duty cycle the LED is at
"normal and desired" brightness. Now you use PWM to reduce
this intensity. In this case, quite to the opposite of your
conclusion, PWM is actually a MORE efficient method than
others. In this case, your nominal power required is 100%
when operating at full brightness and will correspond to the
duty cycle % when operating at other brightness levels. So
operating at 10% duty cycle will require 10% of the power.
Other methods would dissipate 90% elsewhere so that 10% would
be dissipated in the LED and would be HORRIBLE, by
comparison. So you would WANT to use PWM, here, to save
power.

But let's say you are using PWM because you are multiplexing
a complex LED display. So, here, let's say you are
multiplexing by a factor of 5 because you have 5 columns (or
rows -- pick your terminology) to operate. In order to
achieve a "nominal 100% brightness" in a column, you must
drive it at 5 times the nominal current. So if the current is
20mA, nominally, you need to run them at 100mA, but at 20%
duty cycle. The other columns will also be operated at 20%
for their nominal brightness level. To adjust their
brightness from 0% to 100%, you would PWM them from 0% to
20%. In this case, because the LED voltage will be higher at
5X the nominal current, the power dissipated will be more
than just 5X nominal. But the brightness is determined by the
current, not the power. So in this case one could argue that
PWM wastes some power that, had the LEDs had individual
drivers and weren't muxed instead, would be less for the same
effect. But you pay this price because of the convenience and
reduced cost.

Keep in mind that as far as human perceptions go, so long as
the repetition rate is high enough that the brain cannot
follow it, the brightness perceived will be based upon the
average (integral) of the incident light flux. It will not
depend upon the pulse intensity. (There are other factors,
such as the spatial size and spatial frequency, position on
or off axis of the eye, and the surrounding intensities
nearby that also affect perception... but let's keep this
focused.) If you reduce the repetition rate, then at some
point the brain starts to perceive the peak pulse and will
show a change in brightness perception, along with it. But
it's also confounded by the fact that the pulse is being
noticed as well and that usually isn't desired. So the best
rule of thumb to stick with is that your average current
value represents the perceived flux.

The only other rule to keep in mind is that human perception
is logarithmic, so halving the average current does NOT
reduce the apparent brightness in half. To maintain a
constant rate of decline in brightness, you must multiply the
duty cycle by a constant factor for each time unit. So, for
example:

100%
50%
25%
12.5%
6.25%

Would yield constant changes in apparent brightness. If you
achieved those values with fixed time intervals between them,
a human would perceive a "smooth" diminuation in brightness
that appeared linear.

Regardless, PWM is by itself not necessarily inefficient. And
even when you must pay a small price in efficiency because
you are multiplexing and have to use higher pulse currents
because of that, it's still better than the alternative of
paying for individual drives for every LED and not terribly
inefficient, anyway. Other alternatives would be either
excessively expensive for very little gain, or simply worse.

PWM, though, provides better linearity
Click to expand...
Of what? Again, note that human perception is logarithmic. So
while PWM can easily be controlled linearly, it's not going
to be perceived that way if that is how you use it. In fact,
PWM would be more usable as a brightness control if the
hardware could PWM accurately in a logarithmic way -- it's
actually a pain to use PWM correctly for brightness control
if you care about human perceptions of relative brightness.
It's advantage is that it is just easy to apply, is all.

and stable color.
Click to expand...
I guess I should mention something else just to complicate
things (and agree with you.)

If you operate a monochromatic (single) LED at differing
currents (and, consequently, different voltages to achieve
it), then you will get a different wavelength distribution
out of it, too. If you use a spectrophotometer you will see
the shifts. This also means the "color perception" of a
single color LED shifts a little.

So one could argue that keeping the LED current fixed while
PWM'ing to achieve brightness shifts is actually achieving
"stable color" for these reasons (the peak current remains
fixed, just the duty cycle changes.)

But if you are comparing, say, 20mA vs 100mA, then there is
also a color shift in doing so. So I take your point that PWM
achieves "stable color."

But even if I want to use
adjustable current instead of PWM, the current mirror still works:
just attach a voltage-controlled current source to the mirror. So I
think I'm going to stick with that one.
Click to expand...
It's what I'd probably do (or use an IC, if I could find one
that is likely to exist for a while, is readily available,
could handle the dissipation, and is cheap enough.)

Jon
 
"Lauri Alanko" <la@iki.fi> wrote in message
news:krojpi$ush$1@oravannahka.helsinki.fi...
In article <oq5ut8ddooi9f0g0gf3bhcm7gut535btvh@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:
All the
replies I've received have been most pertinent and educational, and
the circuits I've seen seem useful regardless of whether one plugs in
four 2.2 V leds or three 3.6 V leds per series.

---
Indeed, and my entries were intended to illustrate how you could use a
simple, inexpensive single-transistor common emitter circuit to
achieve your stated goals.

But, with no feedback until now, it was impossible to determine
whether or not _my_ time was wasted in trying to help you.

Sorry for not responding to your posts earlier. I was a bit
overwhelmed by the number of replies to what seemed to be a relatively
straightforward query. After the current mirror circuit, which seemed
ideal, the point of the additional suggestions seemed lost to me,
especially since there was no explication of how they would be
superior.

You are suggesting using a resistor as a current limiter, and a
transistor as an on/off switch for PWM. This doesn't seem ideal to me.
Firstly, it requires multiple components per chain (though there is an
obvious variant where there is a single power transistor switching the
supply to all the chains). But more importantly, a resistor is a
fragile current limiter: the current will depend on fluctuations in the
supply voltage and the I-V curves of the leds (which, I hear, are
prone to individual variations). And if a single led shorts, the
current to the others will increase, decreasing their lifetime as
well. I doubt these issues will be very relevant for my toy project,
but I want to learn to do things properly.

The reason I asked about using a _transistor_ as a current limiter is
that transistors are mostly immune to such fluctuations at the
collector, and only their (relatively low) base voltage needs to be
well-regulated. This seems superior to using a resistor, and there is
the added advantage that the same transistor can also be controlled to
provide e.g. PWM.

However, I recently learned that PWM is not actually very efficient
with leds: it seems that leds provide more light per watt when run at
constant low currents than when pulsed at a high current. PWM, though,
provides better linearity and stable color. But even if I want to use
adjustable current instead of PWM, the current mirror still works:
just attach a voltage-controlled current source to the mirror. So I
think I'm going to stick with that one.
Click to expand...
It sort of depends - first of all, many people take total energy for the
light output, so energy lost in a series resistor or linear regulator as
taking away from efficiency.

The most basic PWM is therefore more efficient than dropping some of the
voltage to limit the current.

I've seen various application notes for LED pulse operation with peak pulse
current significantly higher than the max average LED current, the total
dissipation is not exceeded because of the very low duty cycle - the
accepted wisdom is that persistence of vision makes the LED appear to be
much brighter than the *average* (calculated) power would suggest.

There is a *don't exceed* current no matter how narrow you make the pulses,
so read the appnote carefully before doing.
 
On 2013-07-11, Jon Kirwan <jonk@infinitefactors.org> wrote:
On 11 Jul 2013 07:30:08 GMT, Jasen Betts <jasen@xnet.co.nz
wrote:

perhaps next year send $50 to astraweb and receive a terrabyte
of usenet with no use-before date.

Hmm. On first blush, that sounds like a lot. But when I think
about what a terrabyte will likely mean to me... hmm. Do they
carry binaries like alt.binaries.schematics.electronic? (I
guess I can go look and find out... but if you already know,
I wouldn't mind your opinion about it, too.)
Click to expand...
Yeah, as far as I can tell, all the binaries groups are available.
that one certainly is.


--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
 
On 2013-07-11, Jon Kirwan <jonk@infinitefactors.org> wrote:
On Thu, 11 Jul 2013 21:05:10 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:

Oh... well.... Then I will most certainly be dead before I
could use up a 1Tb purchase.

Over the years I've downloaded at least 1Tb from
alt.binaries.e-book.technical

Very likely I'll be dead before I can read that many books & magazines.

Hmm. Haven't looked at that one. And yes, it looks like one
way or another I'll be dead (and still have more capacity to
download.)

By the way, I did get the list of currently suppported groups
at astraweb located at:

http://www.news.astraweb.com/active.html

For anyone else wondering like I was.

No information at all on how long they retain things, though.
Click to expand...
http://www.astraweb.com/tools/stats.html

currently almost 5 years

--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
 
On 2013-07-13, Jon Kirwan <jonk@infinitefactors.org> wrote:
how much of the messages you ignore (or killfile) get downloaded
depends to a large part on the capabilities of your reader and
the server.

I only download headers via NNTP and then, selectively,
download bodies when I care to read them.
Click to expand...
yeah, but does your software use XHDR or HEAD? The former pulls a single
header from several messages whereas the latter pulls all headers from
a single message.

If your killfiles only use four headers, 4 XHDR requests will be more
much more efficient than 100 HEAD requests,


Also headers are often larger than message bodies.

sci.electronics.design is about 200 megbytes per year of message
content (including headers) (I have local retention back to January so
I doubled it) 40000 messages each year and perhaps 200 bytes of NNTP
overhead on each, for another 8 megabytes, and on top of that TCP
overhead, so maybe 220 megabytes per year for S.E.D

Probably lots less than that, then, since most of what I get
from SED remains headers-only.
Click to expand...
Hmm... I can count that.

jasen@gonzo:/var/spool/news/sci/electronics/design$ find -type f -ctime -183 -exec 'sed' '/^$/,$ d' {} ';' | wc
457382 1757014 29908634

Hbout 30 megabytes of headers in the last 183 days.

total message size:
find -type f -ctime -183 -exec cat {} ';' | wc
1567860 8477618 70408901

Hmm, 70 megs, looks like I over-estimated total volume

So 40 megs message body, So the header:body ratio is
approximately 3:4

How much is quoted content?

find -type f -ctime -183 -exec cat {} ';' | sed '/^ *>/ p;d' | wc
643846 4338102 24717942

Almost 25 megs, well over half. (ignoring the quotes by those who use
non-standard quoting styles, mainly Phil A. and one of the political
activists whose handle I don't recall)

so, headers are more almost twice the volume of the new content.

--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
 
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