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| Joel Koltner... |
 Posted: Fri Jul 24, 2009 2:48 pm |
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"Bob.Jones5400 at (no spam) gmail.com" <bob.jones5400 at (no spam) gmail.com> wrote in message
news:89b4fdbf-7731-4a20-983e-db60e0018fc0 at (no spam) e27g2000yqm.googlegroups.com...
[quote:37048ad548]Is there a similar material for visualizing currents?
[/quote:37048ad548]
I'm not aware of a physical material that does this, but it is standard fare
for field solvers -- most all of them will create pretty, color-coded 3D
displays of current densities and animate them for you, if desired. |
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| Jan Panteltje... |
| Posted: Fri Jul 24, 2009 4:27 pm |
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On a sunny day (Fri, 24 Jul 2009 17:33:54 -0400) it happened Phil Hobbs
<pcdhSpamMeSenseless at (no spam) electrooptical.net> wrote in
<x5SdnfqOMf1YtffXnZ2dnUVZ_u2dnZ2d at (no spam) supernews.com>:
[quote:5513150412]So, from 0-10 mA, I'd say even a jellybean LED is linear enough to be
useful.
Cheers!
Rich
Visually, maybe. LEDs have horrible nonlinearities at low current.
That's why optocouplers are so nonlinear.
[/quote:5513150412]
Depends on how low I guess.
Optos are great, and quite linear.
LEDs are actually quite linear at normal currents.
I have used LEDs optocouplers for audio driven by an opamp current source,
as line isolation in phone line interfaces.
You could even buy the thing in one chip: MOC5010
Good enough for audio. |
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| Phil Hobbs... |
| Posted: Fri Jul 24, 2009 4:44 pm |
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Jan Panteltje wrote:
[quote:ade5cde375]On a sunny day (Fri, 24 Jul 2009 17:33:54 -0400) it happened Phil Hobbs
pcdhSpamMeSenseless at (no spam) electrooptical.net> wrote in
x5SdnfqOMf1YtffXnZ2dnUVZ_u2dnZ2d at (no spam) supernews.com>:
So, from 0-10 mA, I'd say even a jellybean LED is linear enough to be
useful.
Cheers!
Rich
Visually, maybe. LEDs have horrible nonlinearities at low current.
That's why optocouplers are so nonlinear.
Depends on how low I guess.
Optos are great, and quite linear.
LEDs are actually quite linear at normal currents.
I have used LEDs optocouplers for audio driven by an opamp current source,
as line isolation in phone line interfaces.
You could even buy the thing in one chip: MOC5010
Good enough for audio.
[/quote:ade5cde375]
With audio, you're using Class A bias of your LED, so you don't see the
problem. Try making a current transfer ratio plot of your average
optocoupler down to microamp input currents--there's a very pronounced toe.
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 |
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| Rich Grise... |
| Posted: Mon Jul 27, 2009 12:39 pm |
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On Fri, 24 Jul 2009 17:33:54 -0400, Phil Hobbs wrote:
[quote:b22d969574]Rich Grise wrote:
So, from 0-10 mA, I'd say even a jellybean LED is linear enough to be
useful.
Visually, maybe. LEDs have horrible nonlinearities at low current.
That's why optocouplers are so nonlinear.
[/quote:b22d969574]
No offense, but I can refute this. I set up an experiment on the lab
bench, with a 4Nsomethingorother, to see how linear its transfer ratio
was, and almost fell out of my chair when my graph was practically
indistinguishable from a straight line.
Once again, 0-10 mA was virtually linear. My intent was to use it
for isolated feedback in a PS we were trying to design, but after
spending about 60 grand, the boss dropped the project.
Thanks,
Rich |
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| Rich Grise... |
| Posted: Mon Jul 27, 2009 12:40 pm |
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On Fri, 24 Jul 2009 18:44:51 -0400, Phil Hobbs wrote:
[quote:791e5c14b3]Jan Panteltje wrote:
On a sunny day (Fri, 24 Jul 2009 17:33:54 -0400) it happened Phil Hobbs
So, from 0-10 mA, I'd say even a jellybean LED is linear enough to be
useful.
Visually, maybe. LEDs have horrible nonlinearities at low current.
That's why optocouplers are so nonlinear.
Depends on how low I guess.
Optos are great, and quite linear.
LEDs are actually quite linear at normal currents.
I have used LEDs optocouplers for audio driven by an opamp current source,
as line isolation in phone line interfaces.
You could even buy the thing in one chip: MOC5010
Good enough for audio.
With audio, you're using Class A bias of your LED, so you don't see the
problem. Try making a current transfer ratio plot of your average
optocoupler down to microamp input currents--there's a very pronounced toe.
OK, you got me here. In my experiment upthread, I never tested the[/quote:791e5c14b3]
setup to currents that low.
Thanks,
Rich |
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| Phil Hobbs... |
| Posted: Mon Jul 27, 2009 1:48 pm |
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Rich Grise wrote:
[quote:8b4c452a62]On Fri, 24 Jul 2009 17:33:54 -0400, Phil Hobbs wrote:
Rich Grise wrote:
So, from 0-10 mA, I'd say even a jellybean LED is linear enough to be
useful.
Visually, maybe. LEDs have horrible nonlinearities at low current.
That's why optocouplers are so nonlinear.
No offense, but I can refute this. I set up an experiment on the lab
bench, with a 4Nsomethingorother, to see how linear its transfer ratio
was, and almost fell out of my chair when my graph was practically
indistinguishable from a straight line.
Once again, 0-10 mA was virtually linear. My intent was to use it
for isolated feedback in a PS we were trying to design, but after
spending about 60 grand, the boss dropped the project.
Thanks,
Rich
[/quote:8b4c452a62]
I suspect that you failed to look down at low currents. Unless you
took, say, 10000 data points. If you really have an opto that's linear
to say, 1 part in 10**3 down to the low microamps, I'm not offended, I'm
delighted. I want some!
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 |
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| Rich Grise... |
| Posted: Mon Jul 27, 2009 5:18 pm |
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On Mon, 27 Jul 2009 11:48:32 -0700, Joerg wrote:
[quote:63689b4328]Rich Grise wrote:
On Fri, 24 Jul 2009 17:33:54 -0400, Phil Hobbs wrote:
Rich Grise wrote:
So, from 0-10 mA, I'd say even a jellybean LED is linear enough to be
useful.
Visually, maybe. LEDs have horrible nonlinearities at low current.
That's why optocouplers are so nonlinear.
No offense, but I can refute this. I set up an experiment on the lab
bench, with a 4Nsomethingorother, to see how linear its transfer ratio
was, and almost fell out of my chair when my graph was practically
indistinguishable from a straight line.
Once again, 0-10 mA was virtually linear. My intent was to use it
for isolated feedback in a PS we were trying to design, but after
spending about 60 grand, the boss dropped the project.
$60k on a SMPS design? Sixty?
thud ... (falling out of chair)
[/quote:63689b4328]
Well, I wasted about three months, on engineer pay, plus everybody
else's time I wasted, and materials and crap.
Maybe it was only about thirty, but the boss decided it was too much,
and I didn't really have the proper training anyway.
Or are you saying that sixty is cheap? ;-)
Thanks,
Rich |
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| krw... |
| Posted: Mon Jul 27, 2009 7:09 pm |
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On Mon, 27 Jul 2009 17:06:54 -0700, Joerg <invalid at (no spam) invalid.invalid>
wrote:
[quote:b6b5392f22]Rich Grise wrote:
On Mon, 27 Jul 2009 11:48:32 -0700, Joerg wrote:
Rich Grise wrote:
On Fri, 24 Jul 2009 17:33:54 -0400, Phil Hobbs wrote:
Rich Grise wrote:
So, from 0-10 mA, I'd say even a jellybean LED is linear enough to be
useful.
Visually, maybe. LEDs have horrible nonlinearities at low current.
That's why optocouplers are so nonlinear.
No offense, but I can refute this. I set up an experiment on the lab
bench, with a 4Nsomethingorother, to see how linear its transfer ratio
was, and almost fell out of my chair when my graph was practically
indistinguishable from a straight line.
Once again, 0-10 mA was virtually linear. My intent was to use it
for isolated feedback in a PS we were trying to design, but after
spending about 60 grand, the boss dropped the project.
$60k on a SMPS design? Sixty?
thud ... (falling out of chair)
Well, I wasted about three months, on engineer pay, plus everybody
else's time I wasted, and materials and crap.
Maybe it was only about thirty, but the boss decided it was too much,
and I didn't really have the proper training anyway.
Thirty is still a lot for one switcher.
Or are you saying that sixty is cheap? ;-)
No, it's not cheap. For this much money my clients get a pretty complex
design done at my office ;-)
But I do make sure that things that others can do for less are done by
others. For example, layouts are either done at the client or we use a
layouter from my network. I do the nasty areas and then he lays out the
whole board. Same with prototype stuffing, there we hire technicians to
do that. Of course, this does not include EMC lab time and other agency
approvals.
[/quote:b6b5392f22]
Yikes! I guess not. They'll quickly eat that much and do crap work
for it. |
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| Rich Grise... |
| Posted: Thu Jul 30, 2009 1:46 pm |
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On Fri, 24 Jul 2009 13:18:15 -0700, Bob.Jones5400 at (no spam) gmail.com wrote:
Visualize Whirled Peas. ;-)
Cheers!
Rich |
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