Philips LED light bulb is comically flattened

I don’t know what’s used in automotive taillights. I’d be a bit surprised if they used dimming at all. Incandescent bulb taillights don’t use dimming. If any dimming is done, it’s done by having two bulbs and only lighting 1 to get a dimmer light.

Most LED tail-lights I’ve seen use an array of LEDs, In that case, dividing the LEDs into two sets (so two interleaved arrays) and turning one or the other set off is a reasonable way to get dimming.

The only reason to use flickering in taillights would be for heat control. The reason you can’t dump amps of current across an LED is because it would overheat. For one gloriously brief moment it’ll be super-bright, then dark forever. But the light output of an LED is roughly proportional to the current through it: an LED will be twice as bright with 200mA and with 100mA of current – and generate twice the heat/use twice the power. If you run the LED at 200mA and 50% duty cycle, it’ll have the same average brightness/heat/power as the 100mA continuous duty. But the eye works better as a peak-detector than average detector, so the 200mA/50% duty cycle LED will appear brighter than the 100mA/continuous LED.

But if they do use flickering for that, there’s no reason to use a frequency as low as 85Hz.

One thing I have noticed with some LEDs, especially red LEDs in dim light, is that they tend (to me) to visibly trail the object they are on. I gather that’s because in dim light the rods act much faster than the cones. It’s freaky to see the power light on a moving hand-held radio look like it’s an inch or so behind the radio itself at twilight. Similarly, I find it a lot easier to see flicker of PWM-driven LEDs by rapidly moving the LED or my head, so the flashes get spread out on my retina.

So to me, it’s easier to see weird effects with red LEDs in dim conditions where the LEDs and I are moving relative to each other – like watching car taillights at night.

Psst, wanna see something really bright?

Try putting a 12" fluorescent tube in a microwave. Preferably one you don’t plan to use for food afterwards.


He/she might have got the frequency wrong, but CFLs are still hard on the eyes. On my eyes, anyway. I wasn’t familiar with the spectrum thing, but I suspect that’s why all fluorescents, compact or otherwise, look “sickly” to me.

This is a very useful discussion! I dislike CFLs, and LEDs can be hit or miss. Those early Philips LED bulbs with the funky yellow plastic work very well, but I’ve got some cheaper Philips LEDs that make a quiet buzzing noise. Glad to hear the flat ones work well, and thanks to all of you for posting information on types of bulbs, dimmers, and other variables.

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I have gotten some good bulbs directly from manufacturers on eBay. There are a lot of options for color (warm/cool) as well as brightness. You also get bulk discounts. When I remodeled my house, purchased an run-down foreclosure recently, I made sure that as many light fixtures as possible all used the same type of bulb. Then, I bought a 20-pack of bulbs at a huge discount. I left the 2009 LEDs in place in the old house as a selling feature.

For those waiting for their old bulbs to burn out, you may wish to check out an online calculator to see how much money you’d save each year by switching. Most LEDs pay for themselves in 3-4 years.

Those still clinging to CFLs should also consider taking their temperature. Some of my old CFLs got to about 230°F, which, in the summertime in an enclosed space like the kitchen with several of those burning, can mean a LOT of extra unwanted heat in the house, which translates into running more air conditioning. I live in the desert southwest, and the summertime electric bills are amazingly steep, as the rates are higher in summer. (I also have solar panels, so I don’t worry so much any more.) Anyway, my LEDs don’t give off much wasted heat, they are generally in the 104°F- 125°F range.

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The sick greenish light is there for a reason. The light intensity is weighted by eye sensitivity-vs-wavelength curve. By blending the phosphor so more gets emitted in green the manufacturer can cook the numbers and get more lumens per watt, for the cost of the light being unusable.

I am holding up with lightbulbs, with LEDs in a few selected places, and waiting for lower cost and better phosphor blends for solid-state lighting. I harbour a deep, seething hate towards CFLs (which they earned by the unholy combination of light quality, slow startup, and Brussel’s ham-handed attempts to force them down my throat), slightly alleviated by occasional stealing from shop recycle bins and salvaging parts. (Did you know you can use the electronics as a ballast for any other kind of fluorescent tube with matching power rating? If the failure cause was a broken filament, which you can find easily with an ohmmeter once you crack the thing open (Dremel is a friend), the rest of the electronics is usually still alive; just attach the two pairs of wires to filaments to another tube and you’re good to go. Excellent way to power e.g. blacklight or disinfectant-ultraviolet tubes.)

On the lighting note, a great thing for winter depressions is a higher-power (I use 100-watt) metalhalide lamp. Also has quite slow startup, but that is a good thing for morning wakeup as it sort of simulates sunrise.

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For some reason I still have a couple boxes of incandescent lights in the garage, as well as some CFLs. My inner cheapskate can’t seen to throw them out while they are still ‘good’, but I replace burnt out bulbs with LEDs as a rule.

I’ll probably just keep the old ones for places like the storage shed, which gets lit for about 10 minutes/month at most. So I guess I have a lifetime supply.

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The “comically flattened shape” is a different way of managing heat. Notice the absence of the massive heat sink you see on other bulbs? Philips distributes their diodes around the perimeter rather than cramming them all into the base along with the rest of the electronics.

Who the hell uses 12" fluorescent tube bulbs for food?


Monsieur Mangetout?

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Just a caution - those graphs aren’t lumens - they’re relative flux percentages. Only dimming down to 30 percent is not a great dimming performance. One thing I really don’t get with that chart is why it goes up to 250% output. They have set the 100% point at 350mA. There must be a reason, but it’s not made clear.

It’s worth noting that Cree also provides specs on the chromaticity change during dimming, which is one of the major weak spots for white (phosphor driving style) LEDs. Those can get into some truly weird colors when the power levels drop, but the Crees here seem to hold their color spectrum as they go down to their lower dimming level.

Even the Crees seem to have difficulty dimming below 30%. I expect that many of us who have been saving energy for decades by using dimmers appreciate the ability of a tungsten bulb to dim right through to zero. It may just be a coincidence that a dimmed tungsten bulb leans into the red, but it’s a happy coincidence. For years I used a pair of 150 watt halogens in the kitchen on a dimmer. They were almost never run at 100%, and were often run at what was likely about 5% or lower – think nightlight level.

My other significant issue with many newer bulbs is the installed base of specialized switches. I have a porch light switch with a solar calculation feature. Give the switch the time, lat and long, and date, and it will allow an option to turn the light on at sunset (and then off at a set time). Since sunset can vary between 4:40pm and 8:03pm, it’s rather handy not having to adjust the timer several times a year. But – that switch is wired “in line”, and requires a load of at least 40 watts to function correctly. Most CFLs and LEDs have too low a power rating to allow the switch to do its job.

I’m hoping that when I finally see LED backyard spotlamps (150W equivalent), I won’t have a similar problem with the sensor light there. CFLs have extremely poor -20C startup performance - and with a sensor-driven lamp, it will almost always be on for only about five minutes at a time.

Lifetime, most likely. LEDs have a specified number of hours of lifetime, defined as the time when their light production drops to a certain percentage of the starting one. Drive them harder than 100% current, get more light, pay with faster deterioration.

That’s because the screwed up way they are dimmed. It should ideally go by feeding the bulb 100% power but telling it by some mechanism (data over mains? local wireless?) that it should throttle down to a percentage of output. The IoT protocols will do a good job here. Will also allow adjusting the light temperature for LED arrays that allow it; there are RGBW LEDs where there is a white one in addition to the RGB ones, and also white-red ones that allow adjusting the color temperature. (Many variants out there. Plus you can lay down your own, from discrete single-color LEDs. If you are adventurous, you can also mix your own phosphor; nobody says it has to be integrated right on the blue one’s chip.) (Todo: try out scraping phosphor off a good quality CFL tube, backlight it with a blue or UV LED…)

Thought: rewire the light circuitry - use a LED array without its own power supply (just barebones LED string), redo the dimmer as a rectifier and high-freq PWM controller…?

Look inside and check out the way the light is switched. You may be able to attach a third wire (ground) to the switch’s own power supply, so it is well-fed and happy, and separate the on/off circuitry.

CFLs suck in so many ways that I cannot comprehend who came up with the idea of using them in non-specialized applications where they are actually warranted.

Philips LED light bulb is comically flattened

Seriously, Boing Boing?

I really thought you guys would be above such blatant flat shaming.


Beyond the issue of cracking open a sealed UL/CSA-certified device, this solution only works for the 5% of the population who can understand it. The alternative is a different switch (not a 40W to 500W switch, but a 0W to 1500W switch) that - by design - taps across to the neutral to power the switch. But - spending $60 just to change a light bulb is a bit much.

Also, there are the oddities of grand-fathered wiring - some of the switch boxes in my house have no neutral line in the switch box. The hot comes in one side, and the switched goes out the other, and that’s all there is in there.

It’s possible that these were not up to code when the wiring was put in (where is that neutral return anyway?) but I can’t sort it out without some major drywall ripping.

We’ll skip over the annoyance of people who wire switch boxes with #10 wiring. Try gettting those back in the box.

Well, there should be a safety ground (gold wire in diagram below). But if you’ve got a metal box, with grounded armored cable coming in or an external ground wire to the box, you won’t even need that. Just the hot and the switched hot.

The neutral’s up in the lamp holder, as shown in the diagram above. It’s often more cost-effective to wire this way, depends on the relative locations of the light, switch, and power source. Most people have at least one overhead light wired this way in their houses. It’s to code.

Aw, you just need to work out more. :smile: If you can afford the copper, it’s always better to go big! Well, #10 is a bit much for anything switched, though, admittedly - #12 should do the job.

That would explain - and be reassuring at the same time. It may be that the next generation of solar timer switches will get their act together, and run on much more limited current. I noted that the last occupancy sensor switch I installed only had ground and two undifferentiated “hot” lines, Moreover, it has a light type compatibility list that includes just about everything out there, and no minimum load requirements. That strongly suggested it could run the switch using the bare minimum of current that can be safely be snitched through even the most picky load.

It did have a ground line as well, but I strongly doubt that it is part of the normal circuit. Although it is likely you could use a hot-ground circuit to power the switch without significant risk, the very idea doesn’t feel safe, and I think it might actually trip the breaker if the circuit is protected by a GFCI breaker.

(edit: s/with significant risk/without significant risk/)

I have a 600w MH lamp, because I get very sad in the dark. Yes, that’s it. Dark. Sad. Definitely.



I have some of these flat ones and they suck. They flicker randomly for seemingly no reason. They were in a hanging lamp in our living room. The expensive Phillips ones work perfect in that same lamp. The cheapest ones I’ve gotten so far were priced low due to an instant rebate through the local power company (Puget Sound Energy). Two normal shaped A19 bulbs for around $6.00. I can’t remember the name now, Greenlight possibly? They seemed generic. But they are nice and bright, can dim without any flicker, and have performed perfectly. I’ve got a mix of various brands around the house. With 100% of the house being on LED, I’ve noticed cheaper electric bills already. I have always wanted LEDs to come into their own, they are so much better in so many ways than CFL.

Ah, here they are:

They are a little directional towards the top. But they do a better job in our porch ceiling lights than a 60 watt bulb. The light is crisp and warm. Our neighborhood is getting LED streetlights that put those ugly, orange-ish, urban-blight-lights to shame.