Driver to drive?

[Phil Hobbs]

Lostgallifreyan wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in news:xoidnU2-
iIbBSu3XnZ2dnUVZ_r6dnZ2d@supernews.com:

Ohhhhhh..... You're using a voltage driver, and trying to trick it into
being a current driver. Bad, bad, bad, bad news.


I thought if constant current config for an LM317 is good enough for the
standard data sheet then it's good enough for me. (And if you look at
the LaserFAQ closely you'll also see that it's good enough for Winfield
Hill, though he wasn't trying to modulate it..) Like I said, part of the fun
is in making the LM317 do weird and wonderful things. It's fun to know that
wherever you have some, you can do some amazing things normally done with
other parts, usually exotic, more costly, with MUCH more complex board
layouts, etc..

Due to the rolloff in the loop gain, the output of a voltage regulator
appears inductive, which will reliably give you a big noise peak if the
output cap is too big, and some ringing if it's too small.

That fits what I see. I've managed to tame it to something respectful. I
think an 'overshoot' that results in a minimum-to-maximum deviation of
about 3 mA along the 'flat' top of a 500 KHz square wave at 160 mA isn't bad.
People who know a lot more than I do have been content with worse.

As Joerg
said, you're way better off using current drive. It isn't difficult,
just an op amp and a Darlington. Use the Darlington's collector as the
output, and sense the current in its emitter. Adding an outboard
current limit is easy then too.


That's what I intend to try too, though I'll try a MOSFET rather than a
darlington. I take it the darlington is to avoid the gate capacitance of a
MOSFET? I can see that it will work because its total Vf will be less than
the laser diode's own. (A quirk my own circuit is exploiting, in a different
way).

I really like Darlingtons for that job, because they have a lot of
transconductance. That makes the current source stiffer, especially at
low V_CE where MOSFETs start to crap out. Their capacitance is much
lower, which is helpful with massively nonlinear loads like laser
diodes. Also, the V_BE of a Darlington is much better controlled and
less drifty than the V_GS of your average MOSFET. Their betas are
usually around 10,000, which means that they're as accurate as the sense
resistor anyway. Quiet, stable, and predictable--just the ticket for
diode laser drivers, I think.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

 

[Phil Hobbs]

Vladimir Vassilevsky wrote:

Phil Hobbs wrote:

Joerg wrote:

Lostgallifreyan wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in
news:FcadnUCm-
5ZRI-3XnZ2dnUVZ_vKdnZ2d@supernews.com:

I rather suspect you're barking up the wrong tree with a SPICE
model of a diode laser...it isn't the terminal voltage you care
about, it's the light output, and that depends on a whole lot of
optical and thermal things that SPICE is never, ever going to get
right. They have widely differing timescales, for one thing, which
SPICE is horrible at, and for another thing, small amounts of
optical feedback have a _huge_ effect on DL performance, including
feeding back to the terminal voltage.


During the transitions, perhaps, but in steady state operation there
seems to be a remarkable electrical similarity between a dead diode
and a live one. What matters is the way the diode responds to hard
electrical changes on the input, as that's what makes the ringing
and damaging overshoots. This is true with NO consideration of
optical nature, and just modelling that alone, realistically for
real laser diodes, is a lot more than we currently have. And likely
not that big an ask, it's just not been done much, it seems.



Ringing? I never had that. Don't drive them through a built-in
inductor

LDs are usually current driven. The prudent way is to impose a
constant DC current, very well stabilized and equipped with belts,
suspenders, cushions, airbags. Then the fast signals are fed in via a
current "robbing" shunt circuit to ground. That pretty much makes
sure you can't fry it.

Seconded. A nice RF transistor in shunt is the ticket. (Anti-snivet
resistors required.)

The high speed LD drivers I've seen used the differential amp topology.
The LD was the load in one of the shoulders; the max. current was set at
the tail. For the faster switching, when the LD is in the "off" state,
it was kept at the bias current little below the threshold of lasing.
This type of circuit can easily modulate the LD at the rates of up to
several GHz; the limits are set by the RF parasitics.

That works great too, and is superior if you need to turn the lasing on
and off without going too far below threshold. The key is that there's
almost no swing at the emitters (especially if you drive them
differentially), so you don't suffer from the poor HF response of the
current source--you can put a choke in series and forget about it.

I'm usually doing something fancy with AC modulation of a CW diode, e.g.
modulation-generated carrier, so the swing is even smaller.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

 

[Phil Hobbs]

Lostgallifreyan wrote:

Vladimir Vassilevsky <nospam@nowhere.com> wrote in
news:8_2dnS4nlv14f-3XnZ2dnUVZ_g2dnZ2d@giganews.com:


Lostgallifreyan wrote:

Vladimir Vassilevsky <nospam@nowhere.com> wrote in news:IMWdnYD_roXLQ-
3XnZ2dnUVZ_rqdnZ2d@giganews.com:


This type of circuit can easily modulate the LD at the rates of up to
several GHz; the limits are set by the RF parasitics.

But what would you do if you were asked to do 'analog' proportional DC
coupled modulations that tracked a continuously varying signal, instead
of high speed switched signalling? And how fast would it go then?
The LDs are VERY nonlinear (light vs current), so I would use voltage to
frequency conversion, PWM, delta sigma or some other pulse modulation
technique. A lot depends on your requirements, however tracking at the
speed of the 1/10 of the pulse rate ballpark should not be a big
problem.


I like that idea. I've considered it but I think it could be more complex
than the simple modulator based on an LM317. I like the real visual linearity
that could result from very fast PWM though. It's another idea I want to try
once I get this LM317 lark worked out of my system.

LDs' output powers are pretty linear with bias current once you're above
threshold, so if Class A bias is OK, you're in pretty good shape. You
can run a power feedback loop using the monitor photodiode if you really
need to, but you usually won't.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

 

[George Herold]

On Jul 29, 9:47 pm, Lostgallifreyan <no-...@nowhere.net> wrote:

George Herold <ggher...@gmail.com> wrote in news:379c1689-21a2-456e-9d3b-
bf5874b7f...@2g2000prl.googlegroups.com:

I love laser diode's.. K. Libbrecht and Jan Hall's RSI article circa
'93?  is the classic current robbing circuit.  I'd been trying to
modulate a LD current driver at high speed.  I read the abstract to
the above article and said.. "no way".  Then I read it and learned
something.

Here's something to consider: I think many posts here are assuming a
switching modulator wheras I am after a continuously proportional and DC
coupled type. I can hybridise with a PWM control, and eventually will go to
that, probably, but for now, what do you do if you want linear control? Never
mind that diode light output isn't at all linear, we might as well start with
what we CAN control... So do we really use a Darlington? I understand that
those are made to switch fast, they're not chosen for a long linear operating
region... So that leaves some fast single stage transistor, and a sense
resistor, and a controller, likely an op-amp.....

Is this getting through? The LM317 in data sheet approved constant
current mode IS just that, though not a shunt mod. But it does the opamp, the
sense resistor, and the hefty transistor to drive up to 1.5A. It's not as
daft as it looks, and it performs better than anyone ever told me it could.

Anyway, assuming I do shunt part of a constant current from the diode, what
might be the simplest way to do it? As far as I know, something like Robin
Bowden's 'Die4drive' circuit might have a basis for this with its MOSFET,
opamp amd sense resistor, but that's not a shunt mod either...

Getting back to the topic, whatever we do, it would REALLY help if we all had
access to some reasonable semblance (electrically) of a single mode laser
diode in spice. It's long overdue. It would save students and schools and
hobbyists a lot of money if it was there. Linear Technology have given us
LTspice to use for free, now we need things like this to put it to use.

In other news, I seem to have dropped alt.lasers from the cross-post list..
Annoying.

"Anyway, assuming I do shunt part of a constant current from the
diode, what
might be the simplest way to do it? As far as I know, something like
Robin
Bowden's 'Die4drive' circuit might have a basis for this with its
MOSFET,
opamp amd sense resistor, but that's not a shunt mod either..."

Yeah, there are lots of copies of the H&L laser diode current driver
on the web. Start with a simple current source (opamp, pass element
(FET) and sense resistor) and then add a second 'tap' into the laser
diode. A resistor works just fine. H&L add two taps. One is op-amp
based and works up to a few MHz and then a 50 ohm resistor for HF
modulation.

George H.

 

[George Herold]

On Jul 29, 9:47 pm, Lostgallifreyan <no-...@nowhere.net> wrote:

George Herold <ggher...@gmail.com> wrote in news:379c1689-21a2-456e-9d3b-
bf5874b7f...@2g2000prl.googlegroups.com:

I love laser diode's.. K. Libbrecht and Jan Hall's RSI article circa
'93?  is the classic current robbing circuit.  I'd been trying to
modulate a LD current driver at high speed.  I read the abstract to
the above article and said.. "no way".  Then I read it and learned
something.

Here's something to consider: I think many posts here are assuming a
switching modulator wheras I am after a continuously proportional and DC
coupled type. I can hybridise with a PWM control, and eventually will go to
that, probably, but for now, what do you do if you want linear control? Never
mind that diode light output isn't at all linear, we might as well start with
what we CAN control... So do we really use a Darlington? I understand that
those are made to switch fast, they're not chosen for a long linear operating
region... So that leaves some fast single stage transistor, and a sense
resistor, and a controller, likely an op-amp.....

Is this getting through? The LM317 in data sheet approved constant
current mode IS just that, though not a shunt mod. But it does the opamp, the
sense resistor, and the hefty transistor to drive up to 1.5A. It's not as
daft as it looks, and it performs better than anyone ever told me it could.

Anyway, assuming I do shunt part of a constant current from the diode, what
might be the simplest way to do it? As far as I know, something like Robin
Bowden's 'Die4drive' circuit might have a basis for this with its MOSFET,
opamp amd sense resistor, but that's not a shunt mod either...

Getting back to the topic, whatever we do, it would REALLY help if we all had
access to some reasonable semblance (electrically) of a single mode laser
diode in spice. It's long overdue. It would save students and schools and
hobbyists a lot of money if it was there. Linear Technology have given us
LTspice to use for free, now we need things like this to put it to use.

In other news, I seem to have dropped alt.lasers from the cross-post list..
Annoying.

"Anyway, assuming I do shunt part of a constant current from the
diode, what
might be the simplest way to do it? As far as I know, something like
Robin
Bowden's 'Die4drive' circuit might have a basis for this with its
MOSFET,
opamp amd sense resistor, but that's not a shunt mod either..."

Yeah, there are lots of copies of the H&L laser diode current driver
on the web. Start with a simple current source (opamp, pass element
(FET) and sense resistor) and then add a second 'tap' into the laser
diode. A resistor works just fine. H&L add two taps. One is op-amp
based and works up to a few MHz and then a 50 ohm resistor for HF
modulation.

George H.

 

[Tim Williams]

"Lostgallifreyan" <no-one@nowhere.net> wrote in message
news:Xns9C585A893Dzoodlewurdle@216.196.109.145...

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in
news:58CdnWEqNIuvS-3XnZ2dnUVZ_vBi4p2d@supernews.com:

snivet

żQué?

Wow, I didn't know people were still using that term. Last time I heard it
was in talking about tube televisions from the 1960s!

Snivets is where the sweep output tube undergoes oscillations (Barkhausen
oscillation) between the plate and screen, when plate voltage is lower than
screen (Vp(sat) typ. 30V for these types, at Vg2 = 125V). It's supposed to
make an electron-beam-driven resonant cavity, producing UHF oscillations
something like a klystron I suppose. The solution is to raise the voltage
on the beam former grid to about 30V.

Can I get a modern definition for "snivets"?

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

 

[Rich Webb]

On Mon, 10 Aug 2009 14:06:39 -0500, "Tim Williams"
<tmoranwms@charter.net> wrote:

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote in
message news:qrq085t8suv2ilk21mrt7a7fp5q5h315nj@4ax.com...
http://www.sodahead.com/question/532683/rahms-brother-dr-ezekiel-emanuel-the-death-czar-obama-health-policy-advisor-announced-a-new-stystem-for-selecting-who-in-the-population-should-be-killeda-federal-system-for-withdrawing-care-from-those-chosen-for-death---do-you-care/

Just how retarded are these blogs (or the bloggists using them)? At this
rate, by next year we won't even need articles, we can simply read the
insane URLs produced.

We're not at that point now?

If we hadn't crossed the line between tragedy and farce before, Sarah
Palin's "Obama Death Panels" remarks pretty much got us a few miles over
the line into Deepest Wingnuttia.

And some people apparently believe it?

Sheesh!

--
Rich Webb Norfolk, VA

 

[AZ Nomad]

On Mon, 10 Aug 2009 11:50:32 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

"When implemented, the Complete Lives system produces a priority curve
on which individuals aged between roughly 15 and 40 years get the most
substantial chance, whereas the youngest and oldest people get chances
that are attenuated... The Complete Lives system justifies preference
to younger people because of priority to the worst-off rather than
instrumental value."

http://www.sodahead.com/question/532683/rahms-brother-dr-ezekiel-emanuel-the-death-czar-obama-health-policy-advisor-announced-a-new-stystem-for-selecting-who-in-the-population-should-be-killeda-federal-system-for-withdrawing-care-from-those-chosen-for-death---do-you-care/

Obama's health program... Hitler Care

You're a loon.

 

[Frank Buss]

Jan Panteltje wrote:

The cheapest PIC this will work in costs 41 cent in quantity.
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74

You are right, even in smaller quantities it is cheaper than the SE95:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PIC12F508-I/SN-ND

Well,
Program memory loaded: 635 word(s)
Configuration loaded: 1 word(s)
ID memory loaded: 0 word(s)
Data memory loaded: 0 byte(s)
Loading complete.

So, few resources used... why use C, makes no sense so close to the hardware with this sort of memory organisation.

635 words doesn't fit in a PIC12F508-I/SN-ND

There are zillions of PICs in use, from mice (the thing you click with), to all sorts of gadgets.
For a temp alert you need no high accuracy, 70 degrees C versus 75 C is OK.
All things have their use, and I would not want a part that you cannot get in a few years.
PICs are the universal building blocks

Ok, if you have a stable voltage supply, 5°C might work. But a change in
0.5 VDC can result in a change of 10°C. So if you use the internal
oscillator as a reference for measuring the WDT and a battery supply, it
would be very difficult to measure the temperature. And the application
note doesn't say anything about aging.

But using the WDT is a nice idea. I wonder if this is possible for other
microcontrollers, too, with independant free running RC oscillators.

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de

 

[Vladimir Vassilevsky]

Tim Williams wrote:

I can't see using anything else at this voltage. Flyback for under
20W maybe, PP for everything else.

Half bridge wastes half the supply
voltage, full bridge burns double conduction losses. PP gets full voltage

Full bridge primary side takes twice as many fets and drivers compared
to PP. This is expensive. Flyback is actually reasonable up to few
hundred watts, if the amplifiers are implemented as ICs with the full
bridge type output.

per half and single conduction losses. RMS current in the windings is
slightly higher because it's half wave per side, but there's tons of space
when you only need four turns or so.

A lot of copper is required for the 100A currents. That doesn't leave
much space.

Tim

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[Spehro Pefhany]

On Mon, 10 Aug 2009 22:18:25 +0200, Frank Buss <fb@frank-buss.de>
wrote:

Jan Panteltje wrote:

The cheapest PIC this will work in costs 41 cent in quantity.
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74

You are right, even in smaller quantities it is cheaper than the SE95:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PIC12F508-I/SN-ND

Well,
Program memory loaded: 635 word(s)
Configuration loaded: 1 word(s)
ID memory loaded: 0 word(s)
Data memory loaded: 0 byte(s)
Loading complete.

So, few resources used... why use C, makes no sense so close to the hardware with this sort of memory organisation.

635 words doesn't fit in a PIC12F508-I/SN-ND

There are zillions of PICs in use, from mice (the thing you click with), to all sorts of gadgets.
For a temp alert you need no high accuracy, 70 degrees C versus 75 C is OK.
All things have their use, and I would not want a part that you cannot get in a few years.
PICs are the universal building blocks

Ok, if you have a stable voltage supply, 5°C might work. But a change in
0.5 VDC can result in a change of 10°C. So if you use the internal
oscillator as a reference for measuring the WDT and a battery supply, it
would be very difficult to measure the temperature. And the application
note doesn't say anything about aging.

Maybe you could use the WDT as a voltage reference to control its own
power supply.

But using the WDT is a nice idea. I wonder if this is possible for other
microcontrollers, too, with independant free running RC oscillators.

Usually they try to make the RC oscillators more stable with
temperature and voltage.

 

[Frank Buss]

Spehro Pefhany wrote:

Maybe you could use the WDT as a voltage reference to control its own
power supply.

This would require some external parts, which maybe would be more expensive
than a small voltage regulator. And I think it would be difficult and the
control loop could oscillate with a low frequency.

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de

 

[Gerhard Hoffmann]

On Fri, 7 Aug 2009 07:41:02 -0700 (PDT), MooseFET <kensmith@rahul.net> wrote:

Notice that I am now suggesting a battery. Unfortunately, batteries
have a bad tempco too. They are very low noise however so it may be
worth the trouble they cause.

This could be interesting:

http://tf.nist.gov/general/pdf/1133.pdf


regards, Gerhard

 

[News]

"bw" <bwegher@hotmail.com> wrote in message
news:h5ptv1$pbu$1@news.eternal-september.org...

"Archimedes' Lever" <OneBigLever@InfiniteSeries.Org> wrote in message
news:050085hkluifp8sp0c3moqfrkofbb43au2@4ax.com...
On Sun, 09 Aug 2009 22:56:56 -0400, clare@snyder.on.ca wrote:

And many engines back in the generator years redlined at about 3600.

You're an idiot. The engines of the 50s and 60s redlined above 5000
rpm.

3600 rpm was the model T years, you ditz.

Wrong.
Model T was 1800 max.
http://www.barefootsworld.net/ford-t-specs.html

In the USA "high speed" engines of the pre-WW2 era were 3600 RPM
http://en.wikipedia.org/wiki/Straight-eight_engine
The flathead ford v8 was the exception at 3200 RPM

After WW2 most engines stayed at 3600 rating, but the "redline" went to
4000 RPM

RPM and compression generally increased in the 20th century as balance and
metal technology advanced.
Europe generally pushed the RPM higher before the USA

It may reverse back to lower revving engines. The Chevy Volt runs by
electric motor propulsion. It was designed to have a constant speed engine
design run at the most efficient speed, turning a genny which provides power
to the electric motor. As the motor demands more power, it puts an
increased magnetic field on the genny. This drags the engine's speed down,
but the engine injects more fuel to maintain the constant speed and keep the
genny turning.

I believe GM may make the engine variable speed, and lower efficiency, as
the customers may be disconcerted at experiencing a constant speed revving
engine. Sounds garbage to me. Who cares about the speed of the engine?

 

[Jan Panteltje]

On a sunny day (Mon, 10 Aug 2009 22:18:25 +0200) it happened Frank Buss
<fb@frank-buss.de> wrote in <18dxv7vqxblme$.ig8tqii71t75.dlg@40tude.net>:

Jan Panteltje wrote:

The cheapest PIC this will work in costs 41 cent in quantity.
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74

You are right, even in smaller quantities it is cheaper than the SE95:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PIC12F508-I/SN-ND

They even want to program it for you

Well,
Program memory loaded: 635 word(s)
Configuration loaded: 1 word(s)
ID memory loaded: 0 word(s)
Data memory loaded: 0 byte(s)
Loading complete.

So, few resources used... why use C, makes no sense so close to the hardware with this sort of memory organisation.

635 words doesn't fit in a PIC12F508-I/SN-ND

OK, have to spend 4 cents more for a 12F509.
But I was sort of generous with including a lot of extra code.. drop the RS232 out and you are there.

There are zillions of PICs in use, from mice (the thing you click with), to all sorts of gadgets.
For a temp alert you need no high accuracy, 70 degrees C versus 75 C is OK.
All things have their use, and I would not want a part that you cannot get in a few years.
PICs are the universal building blocks

Ok, if you have a stable voltage supply, 5°C might work. But a change in
0.5 VDC can result in a change of 10°C. So if you use the internal
oscillator as a reference for measuring the WDT and a battery supply, it
would be very difficult to measure the temperature. And the application
note doesn't say anything about aging.

Yea, but you would most likely use this on a PCB with high power stuff, like power amps,
or switching stuff..
Battery (like in AA or AAA type) stuff is usually made to use extremely low power.

But using the WDT is a nice idea. I wonder if this is possible for other
microcontrollers, too, with independant free running RC oscillators.

Yes, it is just for fun I tried it, after Phil Hobbs needed something like that.
It is in itself not a bad idea to have a temp alert in a case.

 

[Jim Thompson]

On Mon, 10 Aug 2009 15:16:24 -0500, AZ Nomad
<aznomad.3@PremoveOBthisOX.COM> wrote:

On Mon, 10 Aug 2009 11:50:32 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:
"When implemented, the Complete Lives system produces a priority curve
on which individuals aged between roughly 15 and 40 years get the most
substantial chance, whereas the youngest and oldest people get chances
that are attenuated... The Complete Lives system justifies preference
to younger people because of priority to the worst-off rather than
instrumental value."

http://www.sodahead.com/question/532683/rahms-brother-dr-ezekiel-emanuel-the-death-czar-obama-health-policy-advisor-announced-a-new-stystem-for-selecting-who-in-the-population-should-be-killeda-federal-system-for-withdrawing-care-from-those-chosen-for-death---do-you-care/

Obama's health program... Hitler Care

You're a loon.

Be nice. Otherwise, when you get ill, you'll be declared "surplus"
;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

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

 

[daestrom]

Archimedes' Lever wrote:

On Sun, 09 Aug 2009 11:03:48 -0400, daestrom <daestrom@twcny.rr.com
wrote:

This was simply because they were belted to
run at a slower RPM.

No, it is not. Generators were specifically less efficient at lower
engine speeds, and it had NOTHING to do with pulley ratios, you fucking
dipshit. The pulley ratio was only slightly lower, and that was due to
the larger mass that the rotor of the typical generator of the time had.

Guess you've never seen a DC generator that was oversped then. Spin a
DC generator as fast as a modern alternator and the rotor
self-destructs. The wedging won't hold the copper in, and the banding
won't hold the commutator together.

If all you are going to do is make shit up, you should stay out of a
discussion where you tout yourself as knowing about it.

Back at ya. Go look at the pulley ratio on an old engine (say '40s or
'50s) with a DC generator, then go look at a modern auto. Until you've
done that, just shut up and blow away...

daestrom

 

[daestrom]

Archimedes' Lever wrote:

On Sun, 09 Aug 2009 22:54:09 -0400, clare@snyder.on.ca wrote:

On Sun, 09 Aug 2009 10:26:48 -0700, Archimedes' Lever
OneBigLever@InfiniteSeries.Org> wrote:

On Sun, 09 Aug 2009 11:03:48 -0400, daestrom <daestrom@twcny.rr.com
wrote:

This was simply because they were belted to
run at a slower RPM.
No, it is not. Generators were specifically less efficient at lower
engine speeds, and it had NOTHING to do with pulley ratios, you fucking
dipshit. The pulley ratio was only slightly lower, and that was due to
the larger mass that the rotor of the typical generator of the time had.

If all you are going to do is make shit up, you should stay out of a
discussion where you tout yourself as knowing about it.

They WERE less efficient at low speeds, but he is right - they were
also run at much lower speeds for the reason stated.

That is NOT what he stated. He stated that they were run at 1:1 of the
engine speed, and that is what I refuted. You need to learn how to read.

No, you can't read. Find a quote of mine where I mentioned *any*
specific ratio. Now you're just making shit up (as usual).

I only said that the old DC generators couldn't stand more than about 4k
rpm.

You keep claiming the only reason to switch to alternators was because
of efficiency. Others and myself have explained repeatedly that it had
more to do with being able to get a usable voltage output at idle
(thanks to being able to spin them at a higher speed without them
blowing apart).

Anyone that's ever driven an old car with a DC generator can tell you
how the ammeter on the dashboard would go to zero or even slightly
negative (discharge) at idle and would swing over to 'charge' when you
rev up the engine slightly.

Anyone that's ever had a dead battery in one of those old cars will tell
you that after you jump it to get it started, you have to hold the
engine at a fast idle in order for the DC generator to recharge the
battery at all.

Another clue for you (the clueless) is that the headlights on those old
cars would be dimmer at idle than when driving. This is because the
voltage would drop to just the battery voltage when the DC generator was
spinning so slowly and would rise up to the regulator set-point once you
sped up the engine.

You don't have a clue, you can't be taught, so <PLONK>

daestrom

 

[David L. Jones]

Frank Buss wrote:

Mikko Syrjälahti wrote:

I've ordered 2 and 4 layer boards with 0.15/0.15 track/spacing from
them. Quality and communications has been ok.

Any examples of prices and shipping costs? I'm interested especially
in prototype quantities. Other websites publishes some prices on the
front page, but seems like you have to register for pcbcart first to
see some numbers.

Yes, they have recently changed this, you have to sign up to use the Qutoe
function, but it's well worth it. I've never been spammed by them once.
The online quote system is excellent, you even get a qty price breakdown so
you can see whether it's cheaper to order 10 or 20 etc.
Huge range of options (colour, thickness, gold etc)

But if you want some basic prices, around $40 tooling for a small DS board,
around $90 for a more complex 4 layer board.
Boards themslves are as little as a few dollars to say $10 each in small qty
(<10), size and other factors dependent.

Dave.

--
---------------------------------------------
Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/

 

[daestrom]

Archimedes' Lever wrote:

On Sun, 09 Aug 2009 11:03:48 -0400, daestrom <daestrom@twcny.rr.com
wrote:

This was necessary because when the engine was
turning at 3k-4k, you couldn't have the generator spinning much faster
than 4k itself or it would disintegrate from the centrifugal forces.
(unless you want to spend the $ on a variable-ratio belt drive for just
the DC generator).

There are no cars that incorporate variable ratio belt drives in
America. It is too expensive, and there is no need.

And that's why, you illiterate chump, I said what I did. I did *not*
*ever* say they actually were driven by a variable ratio drive.

What I said was the ratio was kept low so as to *not* require such a
drive. Too high a ratio and the generator would self-destruct.

A typical loser tactic, claim that I said something ridiculous and then
argue that I'm clearly wrong. But the text is there for you to read
(and re-read and re-read until you have some comprehension).

daestrom