Lighting flicker meter - Page 1
Forum section: electronics / projects

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 23, 2018, 11:08:08 am
content: Recently suffered some rather bad headaches when working in a particular room here. Found out that the LEDs I'd recently fitted are flickering badly, and this seems to have been the cause.Surprisingly, of four similar bulbs one was flickering strongly at 100Hz when checked with a photodiode and scope, the others not.This got me to to thinking that a lighting flicker meter might be a very marketable idea. It would a give the public a way to find out how much flicker is present with any given light source.Since frequency is important in physiological effect as well as amplitude, I guess it would need to be weighted in some way toward lower frequencies. Is there already any standard for measuring this, I wonder?

author: Zero999
author_rank: Super Contributor
timestamp: November 23, 2018, 01:52:45 pm
content: I don't know whether there's a standard.A cheap and cheerful way to do this would be to add a photo diode to one of those inexpensive portable nano oscilloscopes.I wonder if a phone camera would be capable of picking it up? If so it might be possible to write an app.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 23, 2018, 01:53:07 pm
content: Here's a gadget for listening to flickering light:

author: Siwastaja
author_rank: Super Contributor
timestamp: November 23, 2018, 04:18:01 pm
content: Quote from: Hero999 on November 23, 2018, 01:52:45 pmVery well possible, assuming the camera API gives even the most basic controls.Just set the exposure time to significantly shorter than 10ms (say, 2 ms or less - this isn't a problem because the amount of light input is huge, you may well go below 1ms even on autoexposure near the bulb), and take a statistically significant number (i.e., >1000) randomly timed shots. Plot the amplitude histogram.If you want a single number, maybeavg=0foreach(linear_light_value)avg += linear_light_value;avg /= count;err=0foreach(linear_light_value)err += (linear_ligh_value - avg)^2rms_err = sqrt(err/count)would do, as it would integrate the sum of the difference compared to steady light, but give more (quadratic) weigh to really low/high amplitudes.This would be an elegant "mass market" solution since everybody (except me; my phone is 13 years old now) has a smartphone and can buy the app. And here we are giving this idea out for free.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 23, 2018, 04:49:00 pm
content: Quote from: Hero999 on November 23, 2018, 01:52:45 pmThere is actually a phone app though I'm not sure how reliable that would be. Was thinking along the lines of a cheap LCD scope myself.Did a few tests with the bench scope on LED bulbs from around the place, and a drawer of CFLs which I'd replaced with LEDs. The results were quite worrying- The CFLs mostly didnotflicker, the LEDs mostlydid, having a significant 100Hz modulation on their light intensity.This is a surprising finding, and it brings doubt upon the idea that LEDs are better for your eyes. One two types of LED were totally free of flicker, and these weren't necessarily the most costly ones either. TCP brand were the best tested (AC component <2% of DC photocurrent) along with COBs fed from cheap Chinese inverters which were also flicker-free. Some of the store own-brands were dreadful.All in all, a bit of an eye opener, and maybe lends weight to the argument that old fashioned bulbs (or halogen) are still best for your visual health. Or, if you want to use LEDs youneeda flicker meter.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 23, 2018, 05:33:51 pm
content: Those non-flickering LED lights have ELECTROLYTIC capacitors which FAIL instantly and are TOO BIG so you can't meet the required PCB SIZE and are a CONSPIRACYThis is why the manufacturers are FORCED to produce flickeringcraphigh-quality long-lasting products, surely you agree?(BTW, those non-flickering CFLs have the exact same electrolytic caps as well, for the exact same reason.)Anyway. Just keep buying LED lights. Just don't buy the flickering crap. Usually the cheapest no-name brands flicker. Proper LED lights do not. Once you find a good brand that works for you, keep buying it and recommend it for the others.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 23, 2018, 08:06:01 pm
content: Fluorescents also have phosphor persistence. LED's don't , so LEDs need a smoother supply. After all, tubular FLs have been used for decades and don't have smoothed supplies.Plus I can always buy a new bulb. They don't supply eyeballs in B22 or E27 fittings

author: Siwastaja
author_rank: Super Contributor
timestamp: November 23, 2018, 08:30:38 pm
content: Quote from: IanMacdonald on November 23, 2018, 08:06:01 pmThey do, but the persistence issurprisinglylow - mains-freq-driven FL tubes have been indeed used forages, but people have been complaining about their flicker for ages, as well!Without a capacitor, a LED can flicker much more badly than the traditional fluorescent, but there's another, even more important reason for it: simple, cheap LED lamps have very short conduction duty cycle due to the forward voltage of the LED string being too close to the mains peak, so the light output doesn't follow the rectified sine wave pattern, but only takes a sharp center portion out of it, which may be 20-30% of the time, in the worst bulbs. Outside that region, no light is producedat all. These bulbs are horrible. The only thing that can exceed this level of horror are half-bridge rectified LED lamps but they are luckily extremely rare for general illumination nowadays.

author: Benta
author_rank: Super Contributor
timestamp: November 23, 2018, 08:40:45 pm
content: Quote from: IanMacdonald on November 23, 2018, 04:49:00 pmHow on earth did you getthatidea? Advertising/marketing? If you want quality light, halogen is the answer, certainly not LED or CFL.Those are only relevant for power savings.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 23, 2018, 10:21:51 pm
content: Quote from: Benta on November 23, 2018, 08:40:45 pmYes - overvoltage'd low-voltage halogen (like a 12V halogen bulb driven at 14 or even 15V); or just using a projector lamp which is basically the same, but by design - produces some very beautiful light at about 3400K, even 3500K color temperature. Being at the brink of melting the tungsten, the conversion to light happens at surprisingly good efficiency (for an incandescent bulb, that is - still far from fluorescent or LED). The only downside is the 50 hour lifetime of the bulb...This is the classical cinema/photo studio lighting solution for very good color rendition.This is not a bad idea for really eye-relaxing work lighting. The efficiency is some 3-4x better than on mains voltage incandescents. Designing an incandescent bulb is a compromise between the runtime and efficiency/color temperature. Lowering the voltage/power ratio enables better runtime/efficiency ratio; a 40W bulb at 230V totally sucks (unless youdowant yellow relaxation light and the heat in cold winter evening...), at 110V it's already better, but starts to reallyshinewhen designed for 12V; which allows the bulb designer to choose either massively longer runtime, or massively better efficiency, or part of the both worlds. And, with higher efficiency, comes higher color temperature.Projector and "photo shoot" lamps go for the efficiency, and the 12V halogen spots everyone loved in the 90's go for a bit of both runtime and efficiency.The only sad part is that when the low-voltage, long-life, better-efficiency halogens penetrated the market, for some reason, everybody was designing them exclusively for spot lighting applications, which gave them their typical "90's" reputation. For general illumination, they never really took off.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 24, 2018, 03:59:24 am
content: I remember about incandescent bulbs that had built in diodes or something to drop the voltage in order to allow the use of a shorter but thicker filament, but they didn't achieve popularity before CFLs took over.

author: TheNewLab
author_rank: Frequent Contributor
timestamp: December 18, 2018, 10:16:51 am
content: Hen Hao!, nee na? (OK, bad pinyin spelling...)How did I end up here??Oh, Ian, how about adding a color meter into the device? "two in one stone" stuff?I was thinking of the latter. You can buy color meters that give corrections in Wratten filter CC (CC10, CC20, CC40)But how about 3 digital readouts in in RGB respectively and an overall Kelvin readout display.The flicker rate should be easy a simplified Scope...again, one of thoseminddso iPhone like unitsIf you proceed with the project please let me know!

author: coppercone2
author_rank: Super Contributor
timestamp: December 18, 2018, 10:22:57 am
content: Most lighting sucks for rooms. What I recommend is LED strip lights put behind molding to make aircraft style lighting that reflects off the ceiling, ran with either solid DC or like 500+ Hz PWM.I did this to a room and you can't tell where the lighting is coming from and its real nice compared to having some overly bright object in your field of view like a lamp. I feel like a primitive when I have a single bright light in the room. Or if I can see anything emitting light.Halogens are good too though if you have them as directional lighting in shrouds aiming at stuff like tables and kitchen counter tops.It feels like actual daylight if its distributed and recessed.

author: StillTrying
author_rank: Super Contributor
timestamp: December 18, 2018, 04:14:45 pm
content: http://www.derlichtpeter.de/en/light-flicker/cfd/

author: maukka
author_rank: Unknown
timestamp: December 18, 2018, 05:05:42 pm
content: This is a very crude smartphone app:VISO Flicker testerSome manufacturers have spectrophotometers which also measure flicker, but not very accurately:Gossen MavospecMy method:http://budgetlightforum.com/node/57087Test of various sensors:http://budgetlightforum.com/node/61254

author: schmitt trigger
author_rank: Super Contributor
timestamp: December 18, 2018, 05:16:58 pm
content: Old technology fluorescent magnetic ballasts, in the dual tube versions some had a capacitor in series with the arc current of one of the lamps.That would phase shift that lamp, such that the flicker would be interleaved with the adjacent lamp.