[volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
brooke at pacific.net
Tue Sep 9 21:00:37 EDT 2014
Is there something special about the GR strobe tube that prevents you from using a more modern strobe tube?
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. _______________________________________________
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