Driver to drive?

[Joel Koltner]

<alertjean@rediffmail.com> wrote in message
news:98e3f191-fdd5-4ee2-900d-347854303bf4@j12g2000vbl.googlegroups.com...
"Dave..You are smart..It was an exam question. But I am not convinced
by the answer professor gave me...that FPGAs will takeover standard
cell designs thereby reducing the number of standard cell designs. I
think as the performance and power of FPGAs will be bad compared to SC
designs, SC designs are always going to be winners
and I dont think FPGAs will take over."

The problem is that it isn't defined exactly what "take over" here means. You
and the professor are both right -- FPGAs are definitely replacing what would
have previously been standard cell designers more and more every year, but in
some applications power and performance (or at least performance per dollar)
are critical and FPGAs are unlikely to be competitive -- ever: Such designs
will not be "taken over."

What kind of professor puts, "Do you believe..." questions on an engineering
exam anyway? He might as well have asked you if you believe in
anthropomorphic global warming or the tooth fairy.

 

[Rich Grise]

On Mon, 04 May 2009 09:42:42 -0700, alertjean wrote:

On May 4, 8:58 am, "keith...@gmail.com" <keith...@gmail.com> wrote:
On May 4, 12:46 am, alertj...@rediffmail.com wrote:

Based on trends in mask and design costs for standard cells, vs. FGPA
capabilities, do
you believe the number of new designs per year executed in standard
cells will increase
or decrease in the future as compared with a baseline of 2007 ?

I think it will increase, what do you think ?

I think you're nuts, but you can ignore history at your peril.

Dave..You are smart..It was an exam question. But I am not convinced
by the answer professor gave me...that FPGAs will takeover standard
cell designs thereby reducing the number of standard cell designs. I
think as the performance and power of FPGAs will be bad compared to SC
designs, SC designs are always going to be winners
and I dont think FPGAs will take over.

What's the difference between an "FPGA" and a "standard cell", other than
my (more than likely inaccurate) assumption that an FPGA is simply a
collection of interconnectible standard cells?

I have no doubt someone here will correct me if I'm inaccurate,
misinformed, or am making a WAG and missing the point entirely. ;-)

Cheers!
Rich

 

[mj]

On May 4, 7:52 am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:

I have exactly that here, made it for strobe tests.
White LED too, uses an 8 pin PIC, and 2 transistors to get some high current.
Want the asm source? Could perhaps still find it.

Actually, it's the circuit to pump current through those LEDs that I
need. My code works already. It works, but the light is feeble. The
asm source wouldn't do me much good, since I'm using AVR. (Now, there,
I'm going to get called scum again!)

But I would love to try out your circuit!

Dank je wel!

--Mark

 

[Rich Grise]

On Sun, 03 May 2009 21:21:54 -0700, mj wrote:

I'm looking for ideas on how to make an LED flash so brightly at a low
duty cycle that it's reasonably bright--maybe even close to what it
would be if it were on DC.

Must be finals week again.

Good Luck!
Rich

 

[mj]

On May 4, 2:45 am, D from BC <myrealaddr...@comic.com> wrote:

On Sun, 3 May 2009 21:21:54 -0700 (PDT), mj <eluc...@gmail.com> wrote:
I'm looking for ideas on how to make an LED flash so brightly at a low
duty cycle that it's reasonably bright--maybe even close to what it
would be if it were on DC.

I'm building a project where I need to flash white LEDs very brightly
30-50 times a second at about a 0.4% duty cycle. (I'm strobing a
spinning disk, and want to freeze images near the LED--too high a duty
cycle, and the image blurs.) 0.4% is not much time for an LED to be
on. I've heard that you can drive LEDs to up to 10x their normal
forward current without damage (though I guess lifetime is shortened)
if you keep duty cycle to <= 1%.

To try to get a bright enough flash, I got some 0.5W white LEDs that
can take a max DC forward current of 150 mA, and have about a ~3.6
forward drop, producing an intensity of 130k mcd. (Not too clear on
the mcd part.) And dem suckers is bright when you're pumping even 100
mA through them. Like squint-to-look-at-it bright. They're in a
standard 5mm package (T-1 3/4, what is up with that package name?),
though it's sturdier than most you've probably seen. The LED looks
like it's been lifting weights, and the leads are shorter and fatter.

Anyway, I have two 2n2222's hooked up as a Darlington, with +5 Vcc,
driving the front Q's base with ~15mA (with a microcontroller pin).
There's NO current-limiting resistor on the back end, where the second
transistor's collector is attached to +5v, and the emitter goes
through the LED to ground.

Since the LED is only on 0.4% of the time, max, it still simply isn't
very bright. The strobe works--I can see the frozen image on the
spinning disk--but the light is simply anemic.

So, I'm wondering if anyone here knows how to design a circuit that
can dump an amp and a half through an LED for, say, 200 microseconds
at a time or less, at 20-50 Hz. Or if anyone else has ideas about how
to make LEDs look bright even if they're only on half a percent of the
time.

I'm hoping I won't have to dump the LED idea and go with tiny xenon
strobes--not really into figuring how to design a 50Hz photo strobe at
the moment.

Thanks for anyone that wants to provide some ideas.

mosfet driverhttp://ixdev.ixys.com/DataSheet/99061.pdf

D from BC
myrealaddress(at)comic(dot)com
BC, Canada
Posted to usenet sci.electronics.design

14 amps, well now that ought to do it. :{)

Can someone explain to me why a MOSFET would be better here than a
bipolar? Seems I should be getting enough current through the LED with
my 2n2222 darlington arrangement, but my transistor design skills have
always been modest. And when I learned it, MOSFET drivers were still
exotic, believe it or not. We did only bipolars.

 

[mj]

On May 4, 3:31 am, <castlebravo...@att.net> wrote:

"mj" <eluc...@gmail.com> wrote in message

news:dda2ac06-f0ff-4535-9de3-68576e4a8651@o27g2000vbd.googlegroups.com...

I'm looking for ideas on how to make an LED flash so brightly at a low
duty cycle that it's reasonably bright--maybe even close to what it
would be if it were on DC.

I'm building a project where I need to flash white LEDs very brightly
30-50 times a second at about a 0.4% duty cycle. (I'm strobing a
spinning disk, and want to freeze images near the LED--too high a duty
cycle, and the image blurs.) 0.4% is not much time for an LED to be
on. I've heard that you can drive LEDs to up to 10x their normal
forward current without damage (though I guess lifetime is shortened)
if you keep duty cycle to <= 1%.

To try to get a bright enough flash, I got some 0.5W white LEDs that
can take a max DC forward current of 150 mA, and have about a ~3.6
forward drop, producing an intensity of 130k mcd. (Not too clear on
the mcd part.) And dem suckers is bright when you're pumping even 100
mA through them. Like squint-to-look-at-it bright. They're in a
standard 5mm package (T-1 3/4, what is up with that package name?),
though it's sturdier than most you've probably seen. The LED looks
like it's been lifting weights, and the leads are shorter and fatter.

Anyway, I have two 2n2222's hooked up as a Darlington, with +5 Vcc,
driving the front Q's base with ~15mA (with a microcontroller pin).
There's NO current-limiting resistor on the back end, where the second
transistor's collector is attached to +5v, and the emitter goes
through the LED to ground.

Since the LED is only on 0.4% of the time, max, it still simply isn't
very bright. The strobe works--I can see the frozen image on the
spinning disk--but the light is simply anemic.

So, I'm wondering if anyone here knows how to design a circuit that
can dump an amp and a half through an LED for, say, 200 microseconds
at a time or less, at 20-50 Hz. Or if anyone else has ideas about how
to make LEDs look bright even if they're only on half a percent of the
time.

I'm hoping I won't have to dump the LED idea and go with tiny xenon
strobes--not really into figuring how to design a 50Hz photo strobe at
the moment.

Thanks for anyone that wants to provide some ideas.

how about some of those phillips 1,3 or 5 watt leds used for maglight
replacement with a high current driver.

http://www.luxeonstar.com/

Bob

Those are nice, but they're kind of expensive. I'm actually doing a
dozen of these LEDs. And the .5W ones are *really* bright at 100mA.
If I can't get the 0.5 W ones to work, I'm going to look into tiny
xenon strobes.

 

[Rich Grise]

On Mon, 04 May 2009 08:54:02 -0700, mj wrote:

On May 4, 7:52 am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:

I have exactly that here, made it for strobe tests.
White LED too, uses an 8 pin PIC, and 2 transistors to get some high current.
Want the asm source? Could perhaps still find it.

Actually, it's the circuit to pump current through those LEDs that I
need. My code works already. It works, but the light is feeble. The
asm source wouldn't do me much good, since I'm using AVR. (Now, there,
I'm going to get called scum again!)

But I would love to try out your circuit!

Doesn't anyone teach you googlies about the other side of google? I
just now put "circuit to pump current through an LED", without quotes,
into google's web search window, and got "about 227,000" hits.

Do your own homework.

Good Luck!
Rich

 

[Rich Grise]

On Mon, 04 May 2009 03:57:51 +0100, Eeyore wrote:

jcdrisc@melbpc.org.au wrote:

As a regular reader of the electronics postings I am heartily sick of
all the advertising for clothing, shoes and vanity items. I recall in
the old
days these would be deleted by a moderator.

Only in a moderated group

I can only assume Google's advertising
policies are a bit out of control. We have a situation where the
majority of the group is polluted by this garbage.
I would hope something is done.

Google could easily do one very simple thing that would partly help.
Delete posts linking to blogspot.com but somone inferred a while back
that they own it, so maybe that wouldn't work.

However email filters work rather well and I doubt Google couldn't afford
something similar for Usemet posts.

A concerted bombardment of google with complaints to the top level is
IMHO the only likely answer. Anyone know the addresses of the board
members, senior management etc ?

It would fall on deaf ears. How do you think google got so stinking rich?

Cheers!
Rich

 

[Rich Grise]

On Sun, 03 May 2009 19:45:23 -0700, John Larkin wrote:

On Sun, 3 May 2009 18:19:27 -0700 (PDT), jcdrisc@melbpc.org.au wrote:

As a regular reader of the electronics postings I am heartily sick of
all the
advertising for clothing, shoes and vanity items. I recall in the old
days these would be
deleted by a moderator. I can only assume Google's advertising
policies are a bit out of control. We have a situation where the
majority of the group is polluted by this garbage.
I would hope something is done.

I have Agent set up with a lot of filters, for sex/clothing/money
schemes, things like that. Maybe 5 per cent of the posts that I see
are spam. I do see Agent announcing that it will fetch, say, 200
headers, and then just see a few new posts. It must filter most of
them.

Does googlegroups even have filters?

Thanks,
Rich

 

[Jon Kirwan]

On Mon, 4 May 2009 08:49:44 -0700 (PDT), mj <elucify@gmail.com> wrote:

snip
Actually, I'm actually doing this for a dozen LEDs at once. A rotating
transparent disk has [A-Z0-9 ] printed just inside the circumference
around the circle. A motor spins the disk at 20-50 RPM (controlled by
the MCU with PWM).
snip

Did you mean to say RPM?? At as low as 20 RPM, you'd be talking about
taking 3 seconds to make one revolution.

Jon

 

[Rich Grise]

On Sun, 03 May 2009 17:23:47 -0700, John Larkin wrote:

These crappy RatShack terminal posts are actually conductive!

http://www.radioshack.com/product/index.jsp?productId=2103639

A pair of them leak 12 pA to the chassis at +1 volt. If I ground
myself and hold the plastic screw part of one, it goes up to 20.

So I'll have to replace them with some Pomonas or something. What a
nuisance.

Pity; they do look nice.

Is it really the posts, or is it simply crud? Have you washed them with
some kind of soap with no fragrances or hand lotions, or maybe with Tide,
and rinsed them with DI water followed by minimum 70% IPA, and blown
them dry with clean, dry, oil-free shop air? Don't use acetone - it will
clean them all the way down to bare metal. ;-)

Good Luck!
Rich

 

[Rich Grise]

On Sun, 03 May 2009 22:08:40 -0400, Spehro Pefhany wrote:

On Sun, 3 May 2009 17:32:18 -0700 (PDT), the renowned Greegor
On May 3, 7:23 pm, John Larkin

These crappy RatShack terminal posts are actually conductive!

http://www.radioshack.com/product/index.jsp?productId=2103639

A pair of them leak 12 pA to the chassis at +1 volt. If I ground
myself and hold the plastic screw part of one, it goes up to 20.

So I'll have to replace them with some Pomonas or something. What a
nuisance.

Pity; they do look nice.

0.000000012 Amp? LOL

No, that's 12nA. 12pA is 1/1000 of that:

0.000000000012 A

Doesn't humid air itself have that kind of leakage? ;-)

Cheers!
Rich

 

[Rich Grise]

On Sun, 03 May 2009 19:26:45 -0700, John Larkin wrote:

Somebody could get rich selling special keyboards for googlegroopers,
one with an LOL key.

Don't you mean, for the victims of the gg-ers? ;-)

Cheers!
Rich

 

[Charlie E.]

On Sun, 3 May 2009 20:50:15 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:

In article <49fd38eb$0$21120$9a6e19ea@unlimited.newshosting.com>,
RFI-EMI-GUY wrote:

Eeyore wrote:

RFI-EMI-GUY wrote:

(snip)
:Visible infrared?

Maybe I meant "near infrared". Indeed it is red and very warm light.

Presumably the optical pass-band of the PVC.

What I am seeing seems to contradict the PVC spectral absorption curve.
See link:

http://www.infraredheaters.com/page12.htm

The PVC curve shown is only shown for wavelengths longer than 2
micrometers.

What you are seeing is certainly much shorter wavelength, likely not far
from 700 nm (one common definition of boundary between visible and IR).

My experience is that if white light from sunlight or tungsten is turned
to a warm-looking red by a non-red object, what I see is wavelengths
from around 590-600 nm through the low, maybe mid 700's of nm.

- Don Klipstein (don@misty.com)

You are probably just seeing internal reflection, as in a waveguide,
of those wavelengths down either the body or the interior of the
pipe...

Charlie

 

[Charlie E.]

On Sun, 03 May 2009 10:51:21 -0700, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

RFI-EMI-GUY wrote:

In my house attic, I have several 4 inch white PVC vent stacks which are
simply white PVC drain pipe extending from the wall headers through the
attic and the roof. On the roof, these are covered with lead flashing to
prevent water from getting inside the house. I have been doing a lot of
work in the attic, and have noticed that these pipes "glow" quite
noticeably as a result of the sunlight outside. As this often happens
when the sun is at the horizon and thus at an angle below which direct
coupling into the pipe would be possible, I am very curious as to the
reason that the visible infrared portion is so much more visible than
white light spectrum. Has anyone else noticed this? What is going on?


White PVC sticking out the roof? 4"? Wow. White PVC usually becomes
rotten from UV pretty quickly. If it isn't painted it begins to turn
brown within 2-3 years in our area. After some more years you can
sometimes crumble it by hand.

Around here, it takes considerably less time than that. The pipes I
ran to my pools solar heater were quite dark within a year, even the
ones by the pumphouse that are mostly in the shade!

Charlie

 

[Rich Grise]

On Sun, 03 May 2009 17:58:21 -0700, John Larkin wrote:

On Sun, 3 May 2009 17:32:18 -0700 (PDT), Greegor <Greegor47@gmail.com
On May 3, 7:23 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
These crappy RatShack terminal posts are actually conductive!

http://www.radioshack.com/product/index.jsp?productId=2103639

A pair of them leak 12 pA to the chassis at +1 volt. If I ground
myself and hold the plastic screw part of one, it goes up to 20.

So I'll have to replace them with some Pomonas or something. What a
nuisance.

Pity; they do look nice.

John

0.000000012 Amp? LOL

I just finished machining a couple of big slots in the aluminum box,
where the critical binding posts go, and added a polycarb plate that
the terminal strips mount on. Now the leakage is showing about 100 fA,
basically my measurement limit. It was ugly, machining the
already-"finished" electronics. I tried milling it dry, but that
didn't work, so I wound up getting chips and cutting fluid everywhere.
Had to clean all that up.

It's amazing what a few drops of Tapmatic will do.

Here's the box:

ftp://jjlarkin.lmi.net/99A260A1.JPG

ftp://jjlarkin.lmi.net/99A260A3.JPG

ftp://jjlarkin.lmi.net/99S260A.JPG

Seems to work now.

Geez, John, did you just fall off the turnip truck yesterday? I've been

doing this sort of thing for decades. For steel, practically any ol'
ordinay petroleum-based oil will work, and for aluminum lard, which in
Mexicanese is "manteca". It works like a charm, albeit, as you've noticed,
it makes mell of a hess, but you do get real purty results.[1] ;-)

Cheers!
Rich
[1] yes, I know it should be "really pretty", but I thought the way
I wrote it here would be somehow more poetic, or amusing, or whatever. ;-)

 

[Jon Kirwan]

On Mon, 04 May 2009 17:55:37 GMT, Rich Grise <richgrise@example.net>
wrote:

On Sun, 03 May 2009 21:21:54 -0700, mj wrote:

I'm looking for ideas on how to make an LED flash so brightly at a low
duty cycle that it's reasonably bright--maybe even close to what it
would be if it were on DC.

Must be finals week again.

Not yet. It's the beginning of May, for gosh sake. Finals week is
probably towards the beginning of June.

Jon

 

[Rich the Philosophizer]

On Sun, 03 May 2009 15:09:31 +0000, Jan Panteltje wrote:

http://upload.wikimedia.org/wikipedia/commons/thumb/9/93/Spaghetti.jpg/180px-Spaghetti.jpg

All of these theories are simply ways of rationalizing away the Magnetic
Will, the Cosmic, sentient magnetic essence that holds holds open the
space for the Universe to evolve in.

Also known as The Mother of Everything.

Cheers!
Rich
For more information, please feel free to visit http://www.godchannel.com

 

[Rich the Newsgroup Wacko]

On Mon, 04 May 2009 12:17:57 +0300, Okkim Atnarivik wrote:

What did a string theorist say when his wife caught him in
the bed with another woman?

"But darling, I can explain everything."

Maybe, but what did she say when she caught him in bed with another man?

:-
Rich

 

On May 4, 8:58 am, "keith...@gmail.com" <keith...@gmail.com> wrote:

On May 4, 12:46 am, alertj...@rediffmail.com wrote:

Based on trends in mask and design costs for standard cells, vs. FGPA
capabilities, do
you believe the number of new designs per year executed in standard
cells will increase
or decrease in the future as compared with a baseline of 2007 ?

I think it will increase, what do you think ?

I think you're nuts, but you can ignore history at your peril.

Dave..You are smart..It was an exam question. But I am not convinced
by the answer professor gave me...that FPGAs will takeover standard
cell designs thereby reducing the number of standard cell designs. I
think as the performance and power of FPGAs will be bad compared to SC
designs, SC designs are always going to be winners
and I dont think FPGAs will take over.