- Home LED Flickers - 20 Updates
| tabbypurr@gmail.com: Dec 12 09:16AM -0800 > As an LED is a go/no-go device, flicker is indicative of a condition outside the emitter. Full stop. > Peter Wieck > Melrose Park, PA I know you think you're right about everything, but you're not. LEDs do sometimes go into flickering mode. You could go google if you don't believe me, it's not that hard to do. NT |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Dec 12 09:26AM -0800 > I know you think you're right about everything, but you're not. LEDs do sometimes go into flickering mode. You could go google if you don't believe me, it's not that hard to do. Where does flicker come from? To better understand flickering in lights, consider the theatrical effect known as strobe lighting. This is a deliberate flicker effect that delivers light at certain frequencies, causing the brain to interpret moving objects as if they were in slow motion. These specified frequencies are generally just a few flashes per second, but they are very close to frequencies that cause epileptic seizures. Unintentional flickering in lighting equipment can be traced back to our power companies that designed electricity flow to use alternating current (AC) as opposed to direct current (DC). With AC power, the sine wave will peak both positively and negatively. This leaves it susceptible to being in a range that will cause flickering, or sometimes an audible hum. How to solve LED flickering issues? LED flickering can be tied back to the driver component within the lamp. The essential purpose of the LED driver design is to rely on a simple circuit to control output current, but without altering the frequency, the LED becomes likely to show visible flicker. However, this can be fixed by using constant current drivers, which remove the peaks of the sine wave. Power correction components within the driver circuit must also be addressed. Without this, ripple currents in the power flow will cause flickering. Ultimately if the driver design of the LED bulb meets the requirements of both a stable DC current and ample ripple suppression, there should be no flicker. If flickering is present in your LED lamp (and you are not dimming with it), it was likely created with cheap driver components. The technology in LED lighting has advanced to the point where this should not happen, unfortunately there are companies that care more about their bottom line than the health of their customers. How Dimming Causes LED Flickering Another challenging variable for LED lamps to avoid flickering is through dimming. Most standard wall dimmers work by phase cutting, which removes part of the sine wave and reduces the voltage. However, this can have negative affects on an LED circuit and actually result in the flicker effect being amplified to a potentially dangerous level (3-15Hz range). This is one of the main reasons why it's hard to trust old dimming systems with new LED bulbs. The only way to be sure no flickering will be present is to get LED-specific dimming solutions for your LED lamps. It all comes back to the fact that LED is a long-term investment. In turn it is worth doing research to ensure you are getting a quality LED bulb, and that if you plan to dim with it you are getting an LED dimming system that has been tested as being compatible to the LED bulbs you intend to use. _________________________________________________________________________ Now, show us a link where the emitter is the cause of the flicker, and not the driver. Otherwise, understand that the Bellman's Proof is not a valid argument. Peter Wieck Melrose Park, PA |
| tabbypurr@gmail.com: Dec 12 09:29AM -0800 > Otherwise, understand that the Bellman's Proof is not a valid argument. > Peter Wieck > Melrose Park, PA Man you can be stupid. Go educate yourself. Or not. |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Dec 12 09:47AM -0800 Thought not. Peter Wieck Melrose Park, PA |
| tabbypurr@gmail.com: Dec 12 11:00AM -0800 > Thought not. > Peter Wieck > Melrose Park, PA you've earnt your ignorance and you get to keep it. |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Dec 12 11:09AM -0800 > > Peter Wieck > > Melrose Park, PA > you've earnt your ignorance and you get to keep it. For someone who rears up like an injured virgin when called out, you have lost a priceless opportunity to humiliate your oppressor. That would be earned. Whereas Earnt is correct, it is non-standard and somewhat pretentious. Similar to your inferred virginity. Peter Wieck Melrose Park, PA |
| tabbypurr@gmail.com: Dec 12 11:28AM -0800 > That would be earned. Whereas Earnt is correct, it is non-standard and somewhat pretentious. Similar to your inferred virginity. > Peter Wieck > Melrose Park, PA It seems I overestimated you. |
| mike <ham789@netzero.net>: Dec 12 12:07PM -0800 > As an LED is a go/no-go device, flicker is indicative of a condition outside the emitter. Full stop. > Peter Wieck > Melrose Park, PA I love it when people say "full stop" like that makes 'em right. So, you've never seen a thermal intermittent... Unlikely, maybe. Full Stop, not so much. |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Dec 12 12:44PM -0800 On Wednesday, December 12, 2018 at 3:07:34 PM UTC-5, mike wrote: > I love it when people say "full stop" like that makes 'em right. > So, you've never seen a thermal intermittent... > Unlikely, maybe. Full Stop, not so much. A thermal intermittent would not apply to the emitter. It would very much apply to the driver, socket, contacts, whatever. I have seen my fair share, naturally - and none of them were an emitter fault. Peter Wieck Melrose Park, PA |
| Fox's Mercantile <jdangus@att.net>: Dec 12 03:01PM -0600 > Another challenging variable for LED lamps to avoid flickering > is through dimming. Surprisingly, the two cheap 60 Watt dimmable LEDs I bought at Walmart, work just fine with the old photo cell socket "night light" adapters. Designed to work with incandescent bulbs, I found out they only take month or two to kill halogen bulbs. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| whit3rd <whit3rd@gmail.com>: Dec 12 02:49PM -0800 |
| whit3rd <whit3rd@gmail.com>: Dec 12 02:54PM -0800 > On Wednesday, December 12, 2018 at 12:16:11 PM UTC-5, tabb...@gmail.com wrote: > > I know you think you're right about everything, but you're not. LEDs do sometimes go into flickering mode. > Now, show us a link where the emitter is the cause of the flicker, and not the driver. Oh, it happens; I've had multi-LED panels where handling the PC board (not the power brick) caused/stopped the flicker. Not solder, either, some kind of internal-to-the-LED package or thermal fault. Replaced four or five elements, and the lamp works fine now (though my replacement LEDs were a mismatch for the original 'warm' white). |
| dplatt@coop.radagast.org (Dave Platt): Dec 12 04:22PM -0800 >brick) caused/stopped the flicker. Not solder, either, some kind of internal-to-the-LED >package or thermal fault. Replaced four or five elements, and the lamp works fine now >(though my replacement LEDs were a mismatch for the original 'warm' white). A lot of the cheap Chinese-made LED bulbs for automotive use seem to develop flicker problems. One or more series strings of LEDs start flashing on and off, somewhat randomly, while other strings are unaffected. These don't have a "driver" per se, just a series resistor and (in some cases) a bypass cap. I haven't been able to tell whether the failure is in one of the individual LEDs in the string, or in the solder bonding of the LED to the substrate. I sorta suspect the latter... bad RoHS-safe-solder junctions, perhaps. The flickering seems to be at least partially a thermal cycling problem... LED comes on, chip heats up, bad junction opens, LED cools down, lather/rinse/repeat. The time constant is typically a fraction of a second... more of a blink than a flicker. |
| John-Del <ohger1s@gmail.com>: Dec 12 05:11PM -0800 > A thermal intermittent would not apply to the emitter. It would very much apply to the driver, socket, contacts, whatever. I have seen my fair share, naturally - and none of them were an emitter fault. > Peter Wieck > Melrose Park, PA I've seen plenty of intermittent or even slow to start LED emitter chips. In LCD backlights, I've changed over two thousand of them in the last 5 years. But, the majority of those were either shorted or open, but the intermittent ones busted my ass enough to force a change of procedure in bench testing before the display was reassembled. Several thermal cycles as well as under-volting and over-volting the array will ferret out most intermittents. |
| John-Del <ohger1s@gmail.com>: Dec 12 05:13PM -0800 On Wednesday, December 12, 2018 at 8:11:10 PM UTC-5, John-Del wrote: > > Melrose Park, PA > I've seen plenty of intermittent or even slow to start LED emitter chips. In LCD backlights, I've changed over two thousand of them in the last 5 years. > But, the majority of those were either shorted or open, but the intermittent ones busted my ass enough to force a change of procedure in bench testing before the display was reassembled. Several thermal cycles as well as under-volting and over-volting the array will ferret out most intermittents. I forgot to add that in no case have I seen an LED chip "flicker", at least not in a steady cadence. OP never clarified what exact kind of flicker he had but I think we've gotten off the subject a bit. |
| sceptre@sdf.lonestar.org: Dec 13 05:18AM In article <5448bce3-35a9-480c-b527-069ff31fc16b@googlegroups.com>, >Now, show us a link where the emitter is the cause of the flicker, and not the driver. A Practical Example of GaN-LED Failure Cause Analysis by Application of Combined Electron Microscopy Techniques Page 2: ...after a short time, the blue and white LEDs either started to flicker, showed a reduced light output, or spontaneously failed completely, whereas the red LEDs present in the same module in parallel continued to function correctly. Page 4: The further observation of cross-sections of the nitride layers inside revealed the reasons for the devices' malfunctions. In Figure 4, an example of a cross-section of an LED exhibiting failure type (B) (flickering dark and bright) is shown. One can see that beside the bond foot, the nitride semiconductor layer has slightly lost contact to the back side of the device and, moreover, shows tiny cracks across the layer. http://www.mdpi.com/1996-1944/10/10/1202/pdf Sceptre -- sceptre@sdf.org SDF Public Access UNIX System - http://sdf.org |
| tubeguy@myshop.com: Dec 13 02:58AM -0600 >expects the resistive load of an incandescent that flickers. >> My guess is a cheap electrolytic in the rectifier, but I have never >> really seen a schematic for how they are wired. I have it in my hallway. Standard switch only, no dimmer. Fixture is a common "BOOB LIGHT". (Google that). I haave 3 such fixtures in the house, all have LEDs. Only this one in the hallway flickers. Neither the incan bulb or CFL that used to be in that fixture flickered. So its likely the LED bulb. I bought a bunch of them at Walmart and then Dollar Tree was selling some for ONE DOLLAR (US) for TWO PACK. I stocked up. I am not sure which is in this fixture, but no others flicker from either store..... |
| Fox's Mercantile <jdangus@att.net>: Dec 13 03:24AM -0600 > Tree was selling some for ONE DOLLAR (US) for TWO PACK. I stocked up. > I am not sure which is in this fixture, but no others flicker from > either store..... So, why don't ya just replace the thing and be done with it? -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| PeterSchneider <PeterSchneider@gmail.cn>: Dec 13 11:10AM +0100 > wonder what is causing the flicker? > My guess is a cheap electrolytic in the rectifier, but I have never > really seen a schematic for how they are wired. If the bulb has an capacitive power supply could be a defective rectifier leeds to flickering. |
| Ralph Mowery <rmowery28146@earthlink.net>: Dec 13 10:41AM -0500 In article <sd-dnZMcZ4z1uI_BnZ2dnUU7-NnNnZ2d@giganews.com>, jdangus@att.net says... > > I am not sure which is in this fixture, but no others flicker from > > either store..... > So, why don't ya just replace the thing and be done with it? My thoughts too. I have a celaing fan with 4 bulbs in it. I put LEDs in it a while back replacing the CFLs. I seldom use the fan part, bu the lights stay on from about 9 in the morning to 12 at night almost every day. A few days ago one of the LEDs would go off for about 2 seconds and come on for a short time and off again. I just replaced it. I may open it up just to see one day, but have not taken time to even worry about it. It may have been of the free ones the power company was giving out a few years ago. At one time they gave out about a dozen CFL and then a dozen LEDs a few years later. One and two dollar or less items are just not worth the time to worry about when they last over 6 months. |
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