Finally got around to modifying my Fluke 845ab with LED's
I would probably use green or yellow LEDs, but the white ones should not be a problem.
I built an LED analyzer/integrating sphere and one of the features is a circuit that optically measures the LED driver PWM frequency. It can also detect the minute variance in LED intensity from an LED driven by a 950 kHz boost converter. It also had no problems with a white LED driven at 4 MHz from a signal generator. You see the long persistence phosphors mainly in large lighting LEDs and not in small indicator LEDs.
Hi Mark:
Do you have a web page on the LED analyzer/integrating sphere?
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Mark Sims wrote:
I would probably use green or yellow LEDs, but the white ones should not be a problem.
I built an LED analyzer/integrating sphere and one of the features is a circuit that optically measures the LED driver PWM frequency. It can also detect the minute variance in LED intensity from an LED driven by a 950 kHz boost converter. It also had no problems with a white LED driven at 4 MHz from a signal generator. You see the long persistence phosphors mainly in large lighting LEDs and not in small indicator LEDs.
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I thought that might be the case, the scope waveform shows
no problem. The white LED has multiple spectra output, thought it might have a
better chance having the right wave length, the extra brightness seems to help
with the deficiencies.
From: holrum@hotmail.com
To: volt-nuts@febo.com
Date: Tue, 9 Sep 2014 22:33:45 +0000
Subject: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
I would probably use green or yellow LEDs, but the white ones should not be a problem.
I built an LED analyzer/integrating sphere and one of the features is a circuit that optically measures the LED driver PWM frequency. It can also detect the minute variance in LED intensity from an LED driven by a 950 kHz boost converter. It also had no problems with a white LED driven at 4 MHz from a signal generator. You see the long persistence phosphors mainly in large lighting LEDs and not in small indicator LEDs.
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
Hi Mark,
I have an itty bitty white led, probably called a T-1 size, and it
glows dimly for a long time after you shut it down. They all pretty
well have to.
I think what you are seeing with your analyzer is the blue/UV component
that drives the phosphor element. It will run just as fast as any old
style LED.
I also think that the blue/UV component, which is very bright, is what
is driving Dallas's chopper.
But enough on that. I wasn't trying to criticize, just make mention of
something I noticed in my own work.
Where I got to thinking of this is when I burned out the strobe tube
in my G-R strobotach. Replacement tubes were in the $300 range, so I
knew that would never happen, so I was thinking of making a solid state
replacement using a handful of those wonderful little white LED's.
They would certainly be bright enough, but I'm pretty sure the phosphor
hang would make them unsuitable for stopping motion... your eye would
see a blur instead of the razor sharp image you get with the strobe tube.
-Chuck Harris
Mark Sims wrote:
I would probably use green or yellow LEDs, but the white ones should not be a
problem. I built an LED analyzer/integrating sphere and one of the features is a
circuit that optically measures the LED driver PWM frequency. It can also detect
the minute variance in LED intensity from an LED driven by a 950 kHz boost
converter. It also had no problems with a white LED driven at 4 MHz from a signal
generator. You see the long persistence phosphors mainly in large lighting LEDs
and not in small indicator LEDs. _______________________________________________
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the
instructions there.
Hi Chuck:
Is there something special about the GR strobe tube that prevents you from using a more modern strobe tube?
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Chuck Harris wrote:
Hi Mark,
I have an itty bitty white led, probably called a T-1 size, and it
glows dimly for a long time after you shut it down. They all pretty
well have to.
I think what you are seeing with your analyzer is the blue/UV component
that drives the phosphor element. It will run just as fast as any old
style LED.
I also think that the blue/UV component, which is very bright, is what
is driving Dallas's chopper.
But enough on that. I wasn't trying to criticize, just make mention of
something I noticed in my own work.
Where I got to thinking of this is when I burned out the strobe tube
in my G-R strobotach. Replacement tubes were in the $300 range, so I
knew that would never happen, so I was thinking of making a solid state
replacement using a handful of those wonderful little white LED's.
They would certainly be bright enough, but I'm pretty sure the phosphor
hang would make them unsuitable for stopping motion... your eye would
see a blur instead of the razor sharp image you get with the strobe tube.
-Chuck Harris
Mark Sims wrote:
I would probably use green or yellow LEDs, but the white ones should not be a
problem. I built an LED analyzer/integrating sphere and one of the features is a
circuit that optically measures the LED driver PWM frequency. It can also detect
the minute variance in LED intensity from an LED driven by a 950 kHz boost
converter. It also had no problems with a white LED driven at 4 MHz from a signal
generator. You see the long persistence phosphors mainly in large lighting LEDs
and not in small indicator LEDs. _______________________________________________
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the
instructions there.
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
Thank you Chuck,
I think you have something there, that is probably driving the choppers.
The meter had a little more jitter than before after the mod, that is why I modified the integration filter caps.
I like the slower response anyway.
When I have time I'll share my mods for the Fluke 540b, Much better than before, can transfer at lightning speed.
The suggestion of using a voltage regulator (LM1117) for the 1.35v mercury battery from the EEV Blogs
Didn’t pan out. Its not a reference, it’s a voltage regulator. You don't need accuracy but stability.
Dallas
Date: Tue, 9 Sep 2014 20:30:30 -0400
From: cfharris@erols.com
To: volt-nuts@febo.com
Subject: Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Hi Mark,
I have an itty bitty white led, probably called a T-1 size, and it
glows dimly for a long time after you shut it down. They all pretty
well have to.
I think what you are seeing with your analyzer is the blue/UV component
that drives the phosphor element. It will run just as fast as any old
style LED.
I also think that the blue/UV component, which is very bright, is what
is driving Dallas's chopper.
But enough on that. I wasn't trying to criticize, just make mention of
something I noticed in my own work.
Where I got to thinking of this is when I burned out the strobe tube
in my G-R strobotach. Replacement tubes were in the $300 range, so I
knew that would never happen, so I was thinking of making a solid state
replacement using a handful of those wonderful little white LED's.
They would certainly be bright enough, but I'm pretty sure the phosphor
hang would make them unsuitable for stopping motion... your eye would
see a blur instead of the razor sharp image you get with the strobe tube.
-Chuck Harris
Mark Sims wrote:
I would probably use green or yellow LEDs, but the white ones should not be a
problem. I built an LED analyzer/integrating sphere and one of the features is a
circuit that optically measures the LED driver PWM frequency. It can also detect
the minute variance in LED intensity from an LED driven by a 950 kHz boost
converter. It also had no problems with a white LED driven at 4 MHz from a signal
generator. You see the long persistence phosphors mainly in large lighting LEDs
and not in small indicator LEDs. _______________________________________________
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the
instructions there.
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
On 09/09/2014 09:00 PM, Brooke Clarke wrote:
Hi Chuck:
Is there something special about the GR strobe tube that prevents you
from using a more modern strobe tube?
Extremely special. Google "GR guided arc flash tube". There are some
old GR tech reports on the tube.
It uses a large bulb so it won't melt at very high flash rates and uses
a series of electrodes between the main ones, biased like in a
photomultiplier tube, to keep the arc nice and tight. It quenches so
fast that the xenon afterglow is the main thing that limits its flash rate.
I have two of the earlier GR neon tube based Strobotrons. The neon
actually has less afterglow than xenon but they hadn't discovered the
guided arc principle yet so it isn't as bright. But it's real fast. In
one of them I replaced the tube oscillator with a little microprocessor
board to give it crystal-controlled accuracy. I retained the cool
multi-turn analog speed control to keep it looking authentic.
Linearizing that thing in software was a chore!
John
--
John DeArmond
Tellico Plains, Occupied TN
http://www.fluxeon.com <-- THE source for induction heaters
http://www.neon-john.com <-- email from here
http://www.johndearmond.com <-- Best damned Blog on the net
PGP key: wwwkeys.pgp.net: BCB68D77
Kind of. It is a 7 pin miniature tube, with about
that many electrodes and triggers. Very, very
fast.
I did find a good used tube so I am set for now.
-Chuck
Brooke Clarke wrote:
Hi Chuck:
Is there something special about the GR strobe tube that prevents you from using a
more modern strobe tube?
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html