Re: [time-nuts] Hi Power LED Light power supply...
In message 5058061f.6040...@clanbaker.org, Michael Baker writes: I was wondering, after seeing some 100 watt LED series wired assemblies that were listed at 30-34 VDC @ 2.9A if a number of LEDs could be wired in series and powered directly from a rectified 110 VAC power source. You wouldn't want that, the flickering would be unbearable. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Hm Maybe if an 1:1 isolation transformer is used except that it would be too heavy and large Mike Baker Mike, As long as one is spending on a transformer.. might as well use a step down transformer and use lower voltage lights! Raj ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Hi I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Tuesday, September 18, 2012 1:35 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... LEDs change brightness very fast and will flicker at 120Hz if you do that. Many people can see 120Hz flicker. Also you would not be getting all the brightness you could. Better to low pass filter On Mon, Sep 17, 2012 at 10:26 PM, Michael Baker mp...@clanbaker.org wrote: Time-Nutters-- I was wondering, after seeing some 100 watt LED series wired assemblies that were listed at 30-34 VDC @ 2.9A if a number of LEDs could be wired in series and powered directly from a rectified 110 VAC power source. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Shouldn't be a problem with the standard UV - phosphor style white LED's that are on the market today. The phosphor has a hang time that runs into the minutes, if all of the glowing LED bits in my lamps are an indication. They glow softly for several minutes after turn off. -Chuck Harris Chris Albertson wrote: LEDs change brightness very fast and will flicker at 120Hz if you do that. Many people can see 120Hz flicker. Also you would not be getting all the brightness you could. Better to low pass filter On Mon, Sep 17, 2012 at 10:26 PM, Michael Baker mp...@clanbaker.org wrote: Time-Nutters-- I was wondering, after seeing some 100 watt LED series wired assemblies that were listed at 30-34 VDC @ 2.9A if a number of LEDs could be wired in series and powered directly from a rectified 110 VAC power source. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
In message ac9e4c92327746d4a521facd35d9d...@vectron.com, Bob Camp writes: I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) I suggest you either carry out a couple of experiments yourself, or go a little easy on the irony. CRTs, and LCDs go out of their way to avoid flickering using physical or electronic persistence, whereas a naked LED wil happily flash up to several hundred kHz if you ask it to. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Hi The shutter on a conventional movie projector is very much an on / off device. They run well below 120Hz. The phosphors in a white LED are at least as long persistence as those in a TV set. There are a *lot* of TV's out there that refresh at 60 Hz or less. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Tuesday, September 18, 2012 9:05 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... In message ac9e4c92327746d4a521facd35d9d...@vectron.com, Bob Camp writes: I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) I suggest you either carry out a couple of experiments yourself, or go a little easy on the irony. CRTs, and LCDs go out of their way to avoid flickering using physical or electronic persistence, whereas a naked LED wil happily flash up to several hundred kHz if you ask it to. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
On Tue, Sep 18, 2012 at 5:21 AM, Bob Camp li...@rtty.us wrote: Hi I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) In the old CRT type TV sets, the phosphor has some persistence. Movies are modulated with a square waves, the frame blinks off and goes dark then blinks on. But the LED's brightness is fast enough to track the sine wave and would be bright only for an instant with quick pulses of light. But just as bad as the flicker is that the LED is wasted and spends most of the time being dim. Power supplies are so easy to do that they are NOT the hard part. With LEDS the hard part is the mechanical and optical design. The light must be indirect and defused and to do that correctly and without much waste requires being creative and/or having some metal working skills. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Hi A white LED is like a fluorescent bulb. The actual LED runs at UV and there are phosphors in it to convert the UV to various colors of visible light. The phosphor mix determines the color balance of the LED. It also adds persistence to the output, just like a CRT. I do very much agree that you need a proper supply to run the LED's. Rectified AC is *not* the way to go. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Tuesday, September 18, 2012 12:42 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... On Tue, Sep 18, 2012 at 5:21 AM, Bob Camp li...@rtty.us wrote: Hi I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) In the old CRT type TV sets, the phosphor has some persistence. Movies are modulated with a square waves, the frame blinks off and goes dark then blinks on. But the LED's brightness is fast enough to track the sine wave and would be bright only for an instant with quick pulses of light. But just as bad as the flicker is that the LED is wasted and spends most of the time being dim. Power supplies are so easy to do that they are NOT the hard part. With LEDS the hard part is the mechanical and optical design. The light must be indirect and defused and to do that correctly and without much waste requires being creative and/or having some metal working skills. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
li...@rtty.us said: There are a *lot* of TV's out there that refresh at 60 Hz or less. Many years ago, we had a busted fluorescent light at work. I could see the flicker out of the corner of my eye. I found it annoying, so I'm a firm believer that some people can see flicker in some conditions. (Fortunately, it was in a location where I didn't spend much time.) Direct vision was not a problem. I assumed the lamp was running at 60 Hz rather than 120 and that peripheral vision was better at detecting flicker/motion. Wiki has an interesting page on this stuff: http://en.wikipedia.org/wiki/Flicker_fusion_threshold the rod cells of the human eye have a faster response time than the cone cells, so flicker can be sensed in peripheral vision at higher frequencies than in foveal vision But also: The maximum fusion frequency for rod-mediated vision reaches a plateau at about 15 Hz, whereas cones reach a plateau, observable only at very high illumination intensities, of about 60 Hz (I think that is backwards from the previous line. I'd guess somebody typoed rods-cones.) Note that LEDs without diffusion are high-illumination, so I'm not surprised if some people report flicker troubles. It would be interesting to investigate some examples. I wonder if they are 120 Hz or 60 Hz? More wiki: For the purposes of presenting moving images, the human flicker fusion threshold is usually taken as 16 hertz (Hz). In actual practice, movies are recorded at 24 frames per second, and TV cameras operate at 25 or 30 frames per second, depending on the TV system used. Even though motion may seem to be continuous at 25 or 30 frame/s, the brightness may still seem to flicker objectionably. By showing each frame twice in cinema projection (48 Hz), and using interlace in television (50 or 60 Hz), a reasonable margin of error for unusual viewing conditions is achieved in minimising subjective flicker effects. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
If you all check, they are using LEDs in traffic signals now by the thousands. These are variations of multiple LEDs used in these signals and they are all powered by 115vac thru the traffic controllers. Joe k3wry In a message dated 9/18/2012 1:28:18 A.M. Eastern Daylight Time, mp...@clanbaker.org writes: Time-Nutters-- I was wondering, after seeing some 100 watt LED series wired assemblies that were listed at 30-34 VDC @ 2.9A if a number of LEDs could be wired in series and powered directly from a rectified 110 VAC power source. If enough LEDs are wired in series such that the peak DC voltage from the rectified 110 AC line does not exceed the max current rating of the LEDs this should eliminate any excess current from flowing. Obviously, this does not provide for any safety isolation from the line. Hm Maybe if an 1:1 isolation transformer is used except that it would be too heavy and large Mike Baker -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Hi ... and if you take a hammer to one, they have a cheap little switcher built right into the base of the bulb. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of k3...@aol.com Sent: Tuesday, September 18, 2012 1:24 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Hi Power LED Light power supply... If you all check, they are using LEDs in traffic signals now by the thousands. These are variations of multiple LEDs used in these signals and they are all powered by 115vac thru the traffic controllers. Joe k3wry In a message dated 9/18/2012 1:28:18 A.M. Eastern Daylight Time, mp...@clanbaker.org writes: Time-Nutters-- I was wondering, after seeing some 100 watt LED series wired assemblies that were listed at 30-34 VDC @ 2.9A if a number of LEDs could be wired in series and powered directly from a rectified 110 VAC power source. If enough LEDs are wired in series such that the peak DC voltage from the rectified 110 AC line does not exceed the max current rating of the LEDs this should eliminate any excess current from flowing. Obviously, this does not provide for any safety isolation from the line. Hm Maybe if an 1:1 isolation transformer is used except that it would be too heavy and large Mike Baker -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
On 9/18/12 6:54 AM, Bob Camp wrote: Hi The shutter on a conventional movie projector is very much an on / off device. They run well below 120Hz. Actually, the typical movie projector uses a rotary shutter which runs at twice the frame rate (e.g. 48 flashes/second) and is hardly a fast transition. The actual waveform is more like a trapezoid (imagine a narrow beam of light going through a rotating disk with two sectors in it..) There's also noticeable movement of the film as the shutter is opening and closing, however, your eye/brain is pretty immune to overall image shifts, particularly when it fills the field of view: it's not much different than handling the saccades of your normal eye movements. 24 fps is quite visible to most people (hence interlace on TVs to get 50 or 60 fields/second) The phosphors in a white LED are at least as long persistence as those in a TV set. There are a *lot* of TV's out there that refresh at 60 Hz or less. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Tuesday, September 18, 2012 9:05 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... In message ac9e4c92327746d4a521facd35d9d...@vectron.com, Bob Camp writes: I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) I suggest you either carry out a couple of experiments yourself, or go a little easy on the irony. CRTs, and LCDs go out of their way to avoid flickering using physical or electronic persistence, whereas a naked LED wil happily flash up to several hundred kHz if you ask it to. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
I remember reading that Hollywood played with faster frame rates and found a substantial number of people experience motion sickness. Thomas Knox Date: Tue, 18 Sep 2012 10:51:07 -0700 From: jim...@earthlink.net To: time-nuts@febo.com Subject: Re: [time-nuts] Hi Power LED Light power supply... On 9/18/12 6:54 AM, Bob Camp wrote: Hi The shutter on a conventional movie projector is very much an on / off device. They run well below 120Hz. Actually, the typical movie projector uses a rotary shutter which runs at twice the frame rate (e.g. 48 flashes/second) and is hardly a fast transition. The actual waveform is more like a trapezoid (imagine a narrow beam of light going through a rotating disk with two sectors in it..) There's also noticeable movement of the film as the shutter is opening and closing, however, your eye/brain is pretty immune to overall image shifts, particularly when it fills the field of view: it's not much different than handling the saccades of your normal eye movements. 24 fps is quite visible to most people (hence interlace on TVs to get 50 or 60 fields/second) The phosphors in a white LED are at least as long persistence as those in a TV set. There are a *lot* of TV's out there that refresh at 60 Hz or less. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Tuesday, September 18, 2012 9:05 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... In message ac9e4c92327746d4a521facd35d9d...@vectron.com, Bob Camp writes: I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) I suggest you either carry out a couple of experiments yourself, or go a little easy on the irony. CRTs, and LCDs go out of their way to avoid flickering using physical or electronic persistence, whereas a naked LED wil happily flash up to several hundred kHz if you ask it to. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
The local sandwich shop that I frequent recently switched to LED lighting. When I walk up to the counter I can see the flicker when people's hands are moving. The same applies for LED taillights when a vehicle is moving as well as newer LED tower lighting. Bob On Sep 18, 2012, at 13:15, Hal Murray hmur...@megapathdsl.net wrote: li...@rtty.us said: There are a *lot* of TV's out there that refresh at 60 Hz or less. Many years ago, we had a busted fluorescent light at work. I could see the flicker out of the corner of my eye. I found it annoying, so I'm a firm believer that some people can see flicker in some conditions. (Fortunately, it was in a location where I didn't spend much time.) Direct vision was not a problem. I assumed the lamp was running at 60 Hz rather than 120 and that peripheral vision was better at detecting flicker/motion. Wiki has an interesting page on this stuff: http://en.wikipedia.org/wiki/Flicker_fusion_threshold the rod cells of the human eye have a faster response time than the cone cells, so flicker can be sensed in peripheral vision at higher frequencies than in foveal vision But also: The maximum fusion frequency for rod-mediated vision reaches a plateau at about 15 Hz, whereas cones reach a plateau, observable only at very high illumination intensities, of about 60 Hz (I think that is backwards from the previous line. I'd guess somebody typoed rods-cones.) Note that LEDs without diffusion are high-illumination, so I'm not surprised if some people report flicker troubles. It would be interesting to investigate some examples. I wonder if they are 120 Hz or 60 Hz? More wiki: For the purposes of presenting moving images, the human flicker fusion threshold is usually taken as 16 hertz (Hz). In actual practice, movies are recorded at 24 frames per second, and TV cameras operate at 25 or 30 frames per second, depending on the TV system used. Even though motion may seem to be continuous at 25 or 30 frame/s, the brightness may still seem to flicker objectionably. By showing each frame twice in cinema projection (48 Hz), and using interlace in television (50 or 60 Hz), a reasonable margin of error for unusual viewing conditions is achieved in minimising subjective flicker effects. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
If you take your garden variety boost converter and place a resistor as the load, the current in the inductor is regulated. (Current is vreference over this resistor value.) All these dedicated LED drive chips do is reduce the voltage across the resistor to improve efficiency. In addition, they might have an overvoltage protection scheme. If for some reason the load, namely the LED string, is removed, the boost converter will self destruct. Unlikely to happen if everything is soldered together, but LEDs are external, and possibly connection can get loose. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
On 18 Sep, 2012, at 12:42 , Chris Albertson wrote: On Tue, Sep 18, 2012 at 5:21 AM, Bob Camp li...@rtty.us wrote: Hi I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) In the old CRT type TV sets, the phosphor has some persistence. Movies are modulated with a square waves, the frame blinks off and goes dark then blinks on. But the LED's brightness is fast enough to track the sine wave and would be bright only for an instant with quick pulses of light. Just to add to this... Ontario, Canada originally ran its power grid at 25 Hz. When they switched the grid to 60 Hz in the 1930's some of the industrial power users, particularly in northern Ontario where private (usually hydroelectric) power generators were common, never got around to changing their plants over. Mine and paper mills using 25 Hz power were common as recently as the 1980's, and might still be there for all I know. Standard incandescent light bulbs don't have a lot of persistence when run on 25 Hz power (I assume there might have been a time when you could buy incandescent bulbs designed for 25 Hz, but not in my lifetime). They don't go entirely off, but they get significantly dimmer in the visible spectrum in the dips as the output red-shifts towards the infrared; they follow the sine pretty well. In my teens, when visiting a place using 25 Hz power for lighting, I could initially see an incredibly annoying flicker when I first got there but after a minute or two this would fade and I'd no longer notice it. Some other people would also see the flicker but others, including my parents, couldn't see it at all so there seemed to be variation (maybe age-related, maybe not) among individual abilities to see this. I would hence believe that a 50 Hz flicker must be pretty close to the edge of what can be perceived, so I'm having trouble believing that a flicker at more than twice that rate would be perceptible at all by anyone. Dennis Ferguson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
snip I would hence believe that a 50 Hz flicker must be pretty close to the edge of what can be perceived, so I'm having trouble believing that a flicker at more than twice that rate would be perceptible at all by anyone. snip Oh, but it is. A couple of years ago I bought one of the Chinese 30 LED spot light bulbs for about $8 on ebay. I thought I'd give it a try for a workbench light. When I plugged it in at work (60 Hz power, here) the two guys standing behind me yelled gaahhh at the same time I did. The flicker was horrendous. The earlier comment about peripheral vision also applies, though. It's worse in the periphery than in direct view. The power supply is nothing more than a bridge rectifier, two current limiting resistors, and a filter capacitor. The capacitor obviously wasn't big enough, though, because it flcikered plenty. -John -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dennis Ferguson Sent: Tuesday, September 18, 2012 1:52 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... On 18 Sep, 2012, at 12:42 , Chris Albertson wrote: On Tue, Sep 18, 2012 at 5:21 AM, Bob Camp li...@rtty.us wrote: Hi I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) In the old CRT type TV sets, the phosphor has some persistence. Movies are modulated with a square waves, the frame blinks off and goes dark then blinks on. But the LED's brightness is fast enough to track the sine wave and would be bright only for an instant with quick pulses of light. Just to add to this... Ontario, Canada originally ran its power grid at 25 Hz. When they switched the grid to 60 Hz in the 1930's some of the industrial power users, particularly in northern Ontario where private (usually hydroelectric) power generators were common, never got around to changing their plants over. Mine and paper mills using 25 Hz power were common as recently as the 1980's, and might still be there for all I know. Standard incandescent light bulbs don't have a lot of persistence when run on 25 Hz power (I assume there might have been a time when you could buy incandescent bulbs designed for 25 Hz, but not in my lifetime). They don't go entirely off, but they get significantly dimmer in the visible spectrum in the dips as the output red-shifts towards the infrared; they follow the sine pretty well. In my teens, when visiting a place using 25 Hz power for lighting, I could initially see an incredibly annoying flicker when I first got there but after a minute or two this would fade and I'd no longer notice it. Some other people would also see the flicker but others, including my parents, couldn't see it at all so there seemed to be variation (maybe age-related, maybe not) among individual abilities to see this. Dennis Ferguson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
There are ways for the flicker to be more evident. Don't laugh, but chewing something hard like a pretzel can bring out the flicker. Basically you can get beat patterns between the vibration of your eye and the light flicker. There is a common problem with DLP projectors that use color wheels. You will see reviewers shaking their heads and eat crunchy food in order to see rainbows on the screen. A similar problem occurs with matrixed LED displays mounted on machinery that has vibration. Very common in industrial controls since they like LEDs for readability. When I designed the 2nd generation LED display drivers, I bumped the refresh rate to 500Hz min. That was about 2x the frequency where I ran out of convoluted experiments to detect flicker. On an analog scope, you can display a flat line and have it wiggle by eating something crunchy. I don't have an analog scope on the bench at the moment, otherwise I would figure out the right circumstances to make that happen. The test pattern for flicker detection is to arrange LEDs where a group of them form a recognizable pattern. Take a plus sign as an example. Put the LEDs in an array. Illuminate the LEDs that are not in the symbol out of phase with those in the symbol. Vary the refresh rate. When the eye can see a pattern, the refresh rate is too low. On 9/18/2012 12:06 PM, John Lofgren wrote: snip I would hence believe that a 50 Hz flicker must be pretty close to the edge of what can be perceived, so I'm having trouble believing that a flicker at more than twice that rate would be perceptible at all by anyone. snip Oh, but it is. A couple of years ago I bought one of the Chinese 30 LED spot light bulbs for about $8 on ebay. I thought I'd give it a try for a workbench light. When I plugged it in at work (60 Hz power, here) the two guys standing behind me yelled gaahhh at the same time I did. The flicker was horrendous. The earlier comment about peripheral vision also applies, though. It's worse in the periphery than in direct view. The power supply is nothing more than a bridge rectifier, two current limiting resistors, and a filter capacitor. The capacitor obviously wasn't big enough, though, because it flcikered plenty. -John -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dennis Ferguson Sent: Tuesday, September 18, 2012 1:52 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... On 18 Sep, 2012, at 12:42 , Chris Albertson wrote: On Tue, Sep 18, 2012 at 5:21 AM, Bob Camp li...@rtty.us wrote: Hi I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) In the old CRT type TV sets, the phosphor has some persistence. Movies are modulated with a square waves, the frame blinks off and goes dark then blinks on. But the LED's brightness is fast enough to track the sine wave and would be bright only for an instant with quick pulses of light. Just to add to this... Ontario, Canada originally ran its power grid at 25 Hz. When they switched the grid to 60 Hz in the 1930's some of the industrial power users, particularly in northern Ontario where private (usually hydroelectric) power generators were common, never got around to changing their plants over. Mine and paper mills using 25 Hz power were common as recently as the 1980's, and might still be there for all I know. Standard incandescent light bulbs don't have a lot of persistence when run on 25 Hz power (I assume there might have been a time when you could buy incandescent bulbs designed for 25 Hz, but not in my lifetime). They don't go entirely off, but they get significantly dimmer in the visible spectrum in the dips as the output red-shifts towards the infrared; they follow the sine pretty well. In my teens, when visiting a place using 25 Hz power for lighting, I could initially see an incredibly annoying flicker when I first got there but after a minute or two this would fade and I'd no longer notice it. Some other people would also see the flicker but others, including my parents, couldn't see it at all so there seemed to be variation (maybe age-related, maybe not) among individual abilities to see this. Dennis Ferguson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
On 18 Sep, 2012, at 15:06 , John Lofgren wrote: snip I would hence believe that a 50 Hz flicker must be pretty close to the edge of what can be perceived, so I'm having trouble believing that a flicker at more than twice that rate would be perceptible at all by anyone. snip Oh, but it is. A couple of years ago I bought one of the Chinese 30 LED spot light bulbs for about $8 on ebay. I thought I'd give it a try for a workbench light. When I plugged it in at work (60 Hz power, here) the two guys standing behind me yelled gaahhh at the same time I did. The flicker was horrendous. The earlier comment about peripheral vision also applies, though. It's worse in the periphery than in direct view. The power supply is nothing more than a bridge rectifier, two current limiting resistors, and a filter capacitor. The capacitor obviously wasn't big enough, though, because it flcikered plenty. Or could the problem have instead been that one side of the bridge wasn't working, so you were getting a 60 Hz flicker rather than 120 Hz? Having seen what I am sure was a 50 Hz flicker, I'd believe that 60 Hz might look awful but I still have some doubt about 120 Hz. Dennis Ferguson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
On Tue, Sep 18, 2012 at 2:27 PM, gary li...@lazygranch.com wrote: A similar problem occurs with matrixed LED displays mounted on machinery that has vibration. Very common in industrial controls since they like LEDs for readability. This is very evident on the new L train cars in Chicago. They have a multicolor LED sign for listing the train destination. For me at least the signs are unreadable when I try to read them from another moving train and hard to read from a platform when the structure vibrates. -- Ryan Szekeres KB9TQN ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
That's because the signs are scanned/multiplexed displays. It is not 60/120 Hz flicker. Tom - Original Message - From: Ryan Szekeres ryan.szeke...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, September 18, 2012 3:38 PM Subject: Re: [time-nuts] Hi Power LED Light power supply... On Tue, Sep 18, 2012 at 2:27 PM, gary li...@lazygranch.com wrote: A similar problem occurs with matrixed LED displays mounted on machinery that has vibration. Very common in industrial controls since they like LEDs for readability. This is very evident on the new L train cars in Chicago. They have a multicolor LED sign for listing the train destination. For me at least the signs are unreadable when I try to read them from another moving train and hard to read from a platform when the structure vibrates. -- Ryan Szekeres KB9TQN ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Hi Oddly enough western New York State also had a 25 Hz grid. Something about Niagara Falls / George Westinghouse comes to mind. If as a youngster you rummaged around in the attic you could indeed find 25 Hz gear still sitting up there. Wish I'd kept it rather than parted it out. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dennis Ferguson Sent: Tuesday, September 18, 2012 2:52 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... On 18 Sep, 2012, at 12:42 , Chris Albertson wrote: On Tue, Sep 18, 2012 at 5:21 AM, Bob Camp li...@rtty.us wrote: Hi I suspect those same 120Hz sensitive people would not be able to watch TV or a movie :) In the old CRT type TV sets, the phosphor has some persistence. Movies are modulated with a square waves, the frame blinks off and goes dark then blinks on. But the LED's brightness is fast enough to track the sine wave and would be bright only for an instant with quick pulses of light. Just to add to this... Ontario, Canada originally ran its power grid at 25 Hz. When they switched the grid to 60 Hz in the 1930's some of the industrial power users, particularly in northern Ontario where private (usually hydroelectric) power generators were common, never got around to changing their plants over. Mine and paper mills using 25 Hz power were common as recently as the 1980's, and might still be there for all I know. Standard incandescent light bulbs don't have a lot of persistence when run on 25 Hz power (I assume there might have been a time when you could buy incandescent bulbs designed for 25 Hz, but not in my lifetime). They don't go entirely off, but they get significantly dimmer in the visible spectrum in the dips as the output red-shifts towards the infrared; they follow the sine pretty well. In my teens, when visiting a place using 25 Hz power for lighting, I could initially see an incredibly annoying flicker when I first got there but after a minute or two this would fade and I'd no longer notice it. Some other people would also see the flicker but others, including my parents, couldn't see it at all so there seemed to be variation (maybe age-related, maybe not) among individual abilities to see this. I would hence believe that a 50 Hz flicker must be pretty close to the edge of what can be perceived, so I'm having trouble believing that a flicker at more than twice that rate would be perceptible at all by anyone. Dennis Ferguson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
On Tue, Sep 18, 2012 at 2:46 PM, Tom Miller tmil...@skylinenet.net wrote: That's because the signs are scanned/multiplexed displays. It is not 60/120 Hz flicker. Tom Something new to research. Thanks! -- Ryan Szekeres KB9TQN ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
That is a very fun prank to do. Show someone an o'scope with a flat line on it and hand them a pretzel or carrot. Tell them that you have implanted several sensors into their brain and you want to calibrate them starting with mandibular vibration. I have seriously freaked some people out with this one. Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of gary Sent: Tuesday, September 18, 2012 12:28 To: time-nuts@febo.com Subject: Re: [time-nuts] Hi Power LED Light power supply... There are ways for the flicker to be more evident. Don't laugh, but chewing something hard like a pretzel can bring out the flicker. Basically you can get beat patterns between the vibration of your eye and the light flicker. There is a common problem with DLP projectors that use color wheels. You will see reviewers shaking their heads and eat crunchy food in order to see rainbows on the screen. A similar problem occurs with matrixed LED displays mounted on machinery that has vibration. Very common in industrial controls since they like LEDs for readability. When I designed the 2nd generation LED display drivers, I bumped the refresh rate to 500Hz min. That was about 2x the frequency where I ran out of convoluted experiments to detect flicker. On an analog scope, you can display a flat line and have it wiggle by eating something crunchy. I don't have an analog scope on the bench at the moment, otherwise I would figure out the right circumstances to make that happen. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Only one LED per segment is on. They are arranged in a matrix -- keeps the pin count down to a dull roar. http://www.instructables.com/id/LED-Dot-Matrix-Display/ http://www.electronics-lab.com/projects/misc/013/index.html DaveH -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Ryan Szekeres Sent: Tuesday, September 18, 2012 12:55 To: Tom Miller; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Hi Power LED Light power supply... On Tue, Sep 18, 2012 at 2:46 PM, Tom Miller tmil...@skylinenet.net wrote: That's because the signs are scanned/multiplexed displays. It is not 60/120 Hz flicker. Tom Something new to research. Thanks! -- Ryan Szekeres KB9TQN ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
dennis.c.fergu...@gmail.com said: [context is flicker from light bulbs running on 25 Hz power] I would hence believe that a 50 Hz flicker must be pretty close to the edge of what can be perceived, so I'm having trouble believing that a flicker at more than twice that rate would be perceptible at all by anyone. It depends a lot on the intensity and the modulation percentage. (and other things) LEDs are probably the worst case: very bright (locally) and 100 % modulation if the filter is crappy. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
The LED traffic signals around here are super noisy electrically. They rip up my mobile gear from the AM broadcast band through 2 meters any time we are close to a traffic light. Some are worse than others. If you can find out who makes them then avoid that manufacture like the plague. Al, k9si Date: Tue, 18 Sep 2012 13:23:41 -0400 (EDT) From: k3...@aol.com To: time-nuts@febo.com Subject: Re: [time-nuts] Hi Power LED Light power supply... If you all check, they are using LEDs in traffic signals now by the thousands. These are variations of multiple LEDs used in these signals and they are all powered by 115vac thru the traffic controllers. Joe k3wry ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
On 9/18/12 10:57 AM, Tom Knox wrote: I remember reading that Hollywood played with faster frame rates and found a substantial number of people experience motion sickness. Not so much the frame rate, but generating imagery that isn't realistic.. your eye expects motion blur (particularly in projected images), and if you project a series of very sharp frames with lots of depth of field, it confuses your brain, because it's trying to process out the motion, but the cues are a little bit off. One cause of motion sickness, for that matter, is where the image your eye sees doesn't match the signals from the vestibular canals. The original Star Tours at Disneyland was quite noticeable for this, because it used a lot of rotation movements (which shift the local G vector) to simulate acceleration since it had limited travel on the motion base. i.e. if you keep the forward view constant and showing an acceleration, and tilt your chair back, the force pushing you back into the chair matches what you'd expect from the visual cue, except for the rotation. Some people didn't get affected much, others did (it made me quite nauseous, while a standard roller coaster doesn't). And images that move with a lag relative to your head motion are notorious (early 3 D graphics goggle displays with a Polhemus head position sensor..) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
Time-Nutters-- I was wondering, after seeing some 100 watt LED series wired assemblies that were listed at 30-34 VDC @ 2.9A if a number of LEDs could be wired in series and powered directly from a rectified 110 VAC power source. If enough LEDs are wired in series such that the peak DC voltage from the rectified 110 AC line does not exceed the max current rating of the LEDs this should eliminate any excess current from flowing. Obviously, this does not provide for any safety isolation from the line. Hm Maybe if an 1:1 isolation transformer is used except that it would be too heavy and large Mike Baker -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Hi Power LED Light power supply...
LEDs change brightness very fast and will flicker at 120Hz if you do that. Many people can see 120Hz flicker. Also you would not be getting all the brightness you could. Better to low pass filter On Mon, Sep 17, 2012 at 10:26 PM, Michael Baker mp...@clanbaker.org wrote: Time-Nutters-- I was wondering, after seeing some 100 watt LED series wired assemblies that were listed at 30-34 VDC @ 2.9A if a number of LEDs could be wired in series and powered directly from a rectified 110 VAC power source. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
