Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
One thing that might be hosing things up a bit is white led's don't switch quickly. They are really UV LED's with a bit of fluorescent material between the LED and the world. The fluorescent material will also luminesce for hours after the LED is turned off. Perhaps because the led never shuts off completely, it is biasing the meter up a few tens of microvolts? -Chuck Harris Dallas Smith wrote: Finally got around to modify my Fluke 845ab with LED 's for the chopper circuit. Used the 17 volt windings for LED's (Mouser 941-C513AMSNCW0Y0511 Warm White Round LED) instead of the 130 volt, move red wire on transformer pin 9 to pin 7.This winding is 180 degrees out of phase, so I reversed the steering diodes (CR106 CR107) I left in to help make sure the phase was correct for the LED's when connecting. Change R154 to 6K to set the brightness, selected for good operation of the zero control. Then install jumper to replace C119. Also changed the filter integration response caps C111 to .022uF and C116 to 47uF, this stabilized the jitter to a manageable mode of operation. Meter now works as well or better when the original neon's worked. As the meter originally had this problem, why is the offset reading different when polarity is reversed at the meter input? About 10uV's. Lamp Blocks. ___ 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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Hi Chuck, Its only 84Hz, It had the offset problem long before I made this mod. The new meter at work many decades ago also had this problem. I pick white so the full spectrum would be covered by the Csd's. Checked waveforms with scope, has sharp rising and falling edges. This mod may not be as elegant as a Linear Devices copper mod, but at lest I will not have to mess with the shielded front end. The offset may be due to the bias current in the front end reacting with the different polarities. Dallas Date: Tue, 9 Sep 2014 15:48:01 -0400 From: cfhar...@erols.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's One thing that might be hosing things up a bit is white led's don't switch quickly. They are really UV LED's with a bit of fluorescent material between the LED and the world. The fluorescent material will also luminesce for hours after the LED is turned off. Perhaps because the led never shuts off completely, it is biasing the meter up a few tens of microvolts? -Chuck Harris Dallas Smith wrote: Finally got around to modify my Fluke 845ab with LED 's for the chopper circuit. Used the 17 volt windings for LED's (Mouser 941-C513AMSNCW0Y0511 Warm White Round LED) instead of the 130 volt, move red wire on transformer pin 9 to pin 7.This winding is 180 degrees out of phase, so I reversed the steering diodes (CR106 CR107) I left in to help make sure the phase was correct for the LED's when connecting. Change R154 to 6K to set the brightness, selected for good operation of the zero control. Then install jumper to replace C119. Also changed the filter integration response caps C111 to .022uF and C116 to 47uF, this stabilized the jitter to a manageable mode of operation. Meter now works as well or better when the original neon's worked. As the meter originally had this problem, why is the offset reading different when polarity is reversed at the meter input? About 10uV's. Lamp Blocks. ___ 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. ___ 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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Hi Dallas, The thing is, CdS cells peak sharply at about 560nm, which is green/yellow. They are blind to most of white light... especially to the blues which are prominent in white LED's. White LED's are designed purely for bulk illumination. They have a very slow response so that they won't flicker when used for domestic lighting off of a 50/60Hz power source. There are also green yellow and red LED's that are designed the same way, but there are many that switch quickly too. -Chuck Harris Dallas Smith wrote: Hi Chuck, Its only 84Hz, It had the offset problem long before I made this mod. The new meter at work many decades ago also had this problem. I pick white so the full spectrum would be covered by the Csd's. Checked waveforms with scope, has sharp rising and falling edges. This mod may not be as elegant as a Linear Devices copper mod, but at lest I will not have to mess with the shielded front end. The offset may be due to the bias current in the front end reacting with the different polarities. Dallas ___ 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] 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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
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: hol...@hotmail.com To: volt-nuts@febo.com Date: Tue, 9 Sep 2014 22:33:45 + 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. ___ 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.
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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
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. ___ 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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
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: cfhar...@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. ___ 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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
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 ___ 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] Finally got around to modifying my Fluke 845ab with LED's
No web page, but a little description here. It has changed quite a bit from the original description. Now uses TAOS color sensors. Suppors Melexis IR thermometer chips. Has 16 bit A/Ds. Processor is an ATMEGA 1284. The control program is based on Lady Heather. Besides LEDs it can also charge/discharge/analyze batteries, measure power converter/supply efficiency, etc http://budgetlightforum.com/node/12296 CIrcuit board: http://img69.imageshack.us/img69/3782/luxor.png Sphere in action: http://img515.imageshack.us/img515/4288/spherew.jpg BTW, the PWM sensor is a silicon phototransistor with not much blue light sensitivity... - Do you have a web page on the LED analyzer/integrating sphere? ___ 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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
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 ___ 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.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Hi Mark, What would your PWM sensor circuit do if all of the AC was in the blue, and the white light appeared as a DC bias on the phototransistor? Mark Sims wrote: BTW, the PWM sensor is a silicon phototransistor with not much blue light sensitivity... ___ 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.
