What is with LED light efficiency?

[Charmonium]

Dimming LED's is a tricky business since on the led side of the circuit color output changes with current, so there's a tradeoff there of how to cut power, either by lowering current for greater efficacy as mentioned above, or switching the led on/off rapidly (more common, but often done at insufficient frequency for whatever reason). On the dimmer side, "dimming" circuits designed for incan's also vary in the same way, some lower voltage/current, but most also cycle the power in some matter, so the power converter on-board has to take into account various possibilities.

I thought that all LED bulbs strobe. No? I know that all LED flashlights do. If they strobe then wouldn't the only way to dim them be to reduce the power supplied (voltage/current)?

 

[dullard]

I thought that all LED bulbs strobe. No? I know that all LED flashlights do. If they strobe then wouldn't the only way to dim them be to reduce the power supplied (voltage/current)?

LEDs will use essentially an infinite current. Then they burn themselves up and die. So, the current needs to be controlled in some fashion. More current = more light. Less current = less light. You are correct that you can control the LED current by either turning the current on/off in a strobe fashion or by adjusting the power supplied (which is difficult since the voltage used by the LED changes as it heats, so you need to control the current and not voltage to have a consistent light output).

You can put a capacitor and inductor on the strobed current to turn it into a fairly consistent output. Meaning the LED light itself does not need to strobe.

Typically you'd use an LED driver to have very precise control of the LED output. The problem is that LED drivers are expensive and don't work well with other light sources. 1) You don't want LED drivers in the light switch/socket since that prevents you from using other lightbulbs. Until the LEDs take over and kill off CFLs and incandescents, that limits marketshare. Or, 2) you put the expensive LED driver into the lightbulb itself. Which means every lighbulb you buy has to have complex circuitry that adds a lot to the price and are redundant if you have more than one bulb in a light fixture. This high cost of redundant electronics prevents LEDs from taking over the market. So, you have a chicken and the egg problem. LED lightbulbs can't be made cheap until they take over the market, and LEDs can't take over the market until they become cheap.

So, in general, the answer has been to 3) put crappy cheap electronics in the bulb, which either makes them non-dimmable or severely limits the dimmable range.

 

[Murloc]

LED light fixtures are made without bulbs at all, it's an all in one thing that you throw in the trash when it dies.

It's the bulbs that are going the way of the dodo.

 

[Muse]

I went to sams club yesterday to buy some CFL's and all they had were $5 and $10 LED bulbs 🙁

I'm not ready for the switch yet.

I am so ready for the switch!

Tired of waiting for my kitchen CFL to get reasonably bright, I went to Costco last week and bought a box of ten 9.5w 800 lumen "daylight" bulbs ($17.99).Feit Electric, the brand. I was surprised how bright they are ("60w equivalent"). Instant on, yeah! These don't appear to be directional (recessed). Box says 15,000 hours and the warranty is for 5 years.

I wasn't sure I liked the instantly perceived very bluish tinge, though. Hmm. "Daylight." So, I went to Home Depot a few days ago and all I saw were Daylight and Soft White. They seem to be on the opposite side of the spectrum. Not sure I want Soft White either. Do they make "White"? I see that on the boxes as a possible but couldn't find any at Home Depot.

I thought Costco only sold the best but the FEIT bulbs from Costco are crap. Many of mine have died in less than a year.

Hmm, I guess I should return mine for a refund when I hit Costco on Friday. At the same time I'll hit Home Depot and look to get some Philips LEDs. Maybe get a box of 4 Soft Whites and a box of 4 Daylights, both 60w equivalent and see which I prefer.

 

[dullard]

I am so ready for the switch!

Tired of waiting for my kitchen CFL to get reasonably bright, I went to Costco last week and bought a box of ten 9.5w 800 lumen "daylight" bulbs ($17.99). I was surprised how bright they are ("60w equivalent"). Instant on, yeah! Box says 15,000 hours and the warranty is for 5 years. Feit Electric, the brand.

I wasn't sure I liked the instantly perceived very bluish tinge, though. Hmm. "Daylight." So, I went to Home Depot a few days ago and all I saw were Daylight and Soft White. They seem to be on the opposite side of the spectrum. Not sure I want Soft White either. Do they make "White"? I see that on the boxes as a possible but couldn't find any.

LEDs, by themselves don't have a white color. You can put in several different colors of LEDs to make it look white (like an RGB monitor only has red, green, and blue but they can appear white). Or you can coat the bulb with a chemical (such as phosphor) to absorb the light and re-emit it in a whiter look.

You should be able to find all kinds of LED bulb color temperatures from very blue to very yellow.
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjR483R_PvRAhUH6IMKHSo9BRYQjRwIBw&url=http://mentchism.com/chart/led-color-temperature-chart/&psig=AFQjCNEwfl9qnyNFvwXR3VorGAlLa1_RkA&ust=1486487777240101

Most people that I know don't like the daylight as it is way too blue for them, giving a harsh laboratory feel to their homes. But, it has its purposes. For example, you can easily tell blacks and dark navy blues apart in that light. So, I like the daylight color in the closet.

The problem is that these coatings add cost and reduce light output (meaning they have to put in a higher power LED to compensate). So, getting the color you want may not be in the budget that you wanted to spend.

 

[dainthomas]

Ikea has great bulbs too, and usually at a good price. Went there yesterday and they had two packs of 400lm bulbs for $2. These were clearance though as I think they're usually in the $4 range.

 

[freeskier93]

LEDs will use essentially an infinite current. Then they burn themselves up and die. So, the current needs to be controlled in some fashion. More current = more light. Less current = less light. You are correct that you can control the LED current by either turning the current on/off in a strobe fashion or by adjusting the power supplied (which is difficult since the voltage used by the LED changes as it heats, so you need to control the current and not voltage to have a consistent light output).

You can put a capacitor and inductor on the strobed current to turn it into a fairly consistent output. Meaning the LED light itself does not need to strobe.

Typically you'd use an LED driver to have very precise control of the LED output. The problem is that LED drivers are expensive and don't work well with other light sources. 1) You don't want LED drivers in the light switch/socket since that prevents you from using other lightbulbs. Until the LEDs take over and kill off CFLs and incandescents, that limits marketshare. Or, 2) you put the expensive LED driver into the lightbulb itself. Which means every lighbulb you buy has to have complex circuitry that adds a lot to the price and are redundant if you have more than one bulb in a light fixture. This high cost of redundant electronics prevents LEDs from taking over the market. So, you have a chicken and the egg problem. LED lightbulbs can't be made cheap until they take over the market, and LEDs can't take over the market until they become cheap.

So, in general, the answer has been to 3) put crappy cheap electronics in the bulb, which either makes them non-dimmable or severely limits the dimmable range.

"Strobing", aka PWM, does not control current. You still need a current limiting device, like a resistor, to limit current. PWM changes the perception of brightness by changing the average power.

Also, constant current drivers are not complicated circuits. It's like electronics 101 (for an engineer)...

LED drivers tend to be a bit more complicated then a simple constant current driver, or use more sophisticated methods of driving constant current to boost efficiency. Most also handle input voltage regulation. Household LEDs also have to handle the fact that the input is 120V AC.

I wouldn't be surprised if some of the really cheap bulbs are nothing more then the LEDs and some big resistors in essentially a half wave rectifier set up. Might explain why some are stupidly inefficient.

 

[dullard]

"Strobing", aka PWM, does not control current. You still need a current limiting device, like a resistor, to limit current. PWM changes the perception of brightness by changing the average power.

Also, constant current drivers are not complicated circuits. It's like electronics 101 (for an engineer)...

Yes, you probably need a resistor or something to limit current. But, not necessarily if the incoming voltage is near the forward voltage drop of the LED.

Constant current drivers are complicated compared to the incandescent bulbs they are replacing (which is just a wire with resistance). Any time you add in a circuit board, inductor, resistors, PWM, capacitor, and possibly a few other components into a ~$0.10 goal for the total bill of materials, it is complicated to hit that price point.

 

[WHAMPOM]

Anybody know if the Walmart LED's are any good?

The ones I bought there are. Non dimmable and brighter then the ones/60 watt bulbs, they are supposed to replace too.

 

[slag]

I bought a ton of LED bulbs from menards a month or so ago. Something special about having to replace the bulb every 13 years vs 1-2 for traditional or 4-5 for CFL (that's about what we get out of them it seems). They don't get hot either which is nice unlike the incandescants they replaced. Also, some A9 bulbs have a diffuser which make them non directional and they look just like "regular" incandescant bulbs.

 

[OverVolt]

I bought a ton of LED bulbs from menards a month or so ago. Something special about having to replace the bulb every 13 years vs 1-2 for traditional or 4-5 for CFL (that's about what we get out of them it seems). They don't get hot either which is nice unlike the incandescants they replaced. Also, some A9 bulbs have a diffuser which make them non directional and they look just like "regular" incandescant bulbs.

This is about as close to a compliment as you can get from slag.

Slag must be really loving them LED A9's.

 

[agent00f]

I thought that all LED bulbs strobe. No? I know that all LED flashlights do. If they strobe then wouldn't the only way to dim them be to reduce the power supplied (voltage/current)?

Strobing is the cheaper way so most consumer products do it, and they do so at some fixed freq, usually some hundreds hz. The way they almost always dim is by reducing the on duration of the strobe.

Also the other reason mentioned for strobing is that varying current changes output color somewhat, or even drastically for very low power/output. This is significant enough that particularly with more sensitive applications like lcd backlight, or oled, the driver will strobe at least for lower brightnesses, even if that's less efficient for very power sensitive application.

LEDs will use essentially an infinite current. Then they burn themselves up and die. So, the current needs to be controlled in some fashion. More current = more light. Less current = less light. You are correct that you can control the LED current by either turning the current on/off in a strobe fashion or by adjusting the power supplied (which is difficult since the voltage used by the LED changes as it heats, so you need to control the current and not voltage to have a consistent light output).

You can put a capacitor and inductor on the strobed current to turn it into a fairly consistent output. Meaning the LED light itself does not need to strobe.

Typically you'd use an LED driver to have very precise control of the LED output. The problem is that LED drivers are expensive and don't work well with other light sources. 1) You don't want LED drivers in the light switch/socket since that prevents you from using other lightbulbs. Until the LEDs take over and kill off CFLs and incandescents, that limits marketshare. Or, 2) you put the expensive LED driver into the lightbulb itself. Which means every lighbulb you buy has to have complex circuitry that adds a lot to the price and are redundant if you have more than one bulb in a light fixture. This high cost of redundant electronics prevents LEDs from taking over the market. So, you have a chicken and the egg problem. LED lightbulbs can't be made cheap until they take over the market, and LEDs can't take over the market until they become cheap.

So, in general, the answer has been to 3) put crappy cheap electronics in the bulb, which either makes them non-dimmable or severely limits the dimmable range.

There's almost no practical way to control by light output per se, even with current control since if voltage varies so does the power, nevermind efficacy. In practice I don't think anyone bothers with smoothing the pulsed output since it's easier to just increase the pwm freq.

 

[slag]

This is about as close to a compliment as you can get from slag.

Slag must be really loving them LED A9's.

20 or so A9s, mostly BR30s

??

I don't mean to come off as pessimistic. Sorry if I offended you.

Joe

 

[luv2liv]

i got LED from HomeDepot. the box said 10 years warranty!
2 out of the 20 bulbs i got failed after 4 months. lol

 

[Scarpozzi]

I put in 5, 4" recessed can lights in my kitchen about 4-5 years ago for task lighting. The only way to get good light on those was to go with 50 watt halogen bulbs. Last year, I went on Amazon and picked up a 5 or 6 pack of bulbs for around $30...PAR20 bulbs. I waited until I had a few bulbs blow before I made the switch. 5X50 = 250 watts. Even if each bulb was 10 watts, the savings is pretty amazing. I've replaced all of the 4-5 bulb bathroom fixtures I have with LEDs too.

I don't care for CFLs. They're cheaper, but their lifespan is greatly overstated. The manufacturers are putting cheap power converters in them and they typically are dying prematurely. Rather than lasting 5+ years, they're only lasting 1-2 before the circuitry fails. I've had some die in a few months. Most are manufactured by a few major companies in China, sold in bulk, and rebranded, so you can't trust any markings on them. LEDs will likely follow suit unless you buy from GE or Sylvania or another company you can follow up with on quality that may have their own manufacturing.

My electric bill started in the $200-350 range when I first bought my current home in 2009. Since then, I've just about doubled the square footage to near 3500 sq ft, updated my heating/cooling system, switched to natural gas heat....a natural gas tankless water heater, and CFL/LEDs. My electric bill in December was $105.....it was $96 this past month. I have 2 kids and we've got multiple TVs, etc...lights are always on in the house. Energy savings can be crazy just by making a few changes. I'm going to be taking a hit when I install a second heating/cooling unit, but plan on going solar in another 5 years with a heat exchanger and radiant heat as a side project....so maybe some of that will offset in the winter if I can find a cheap way to build it without having to buy a lot of stuff. (plan is to recycle parts and build everything from junk except for the evacuated tubes)

 

[DCal430]

The Costco Feit bulbs are so bad, and looking at the reviews seems like I am not the only one with issues.

https://m.costco.com/Feit-LED-60W-Replacement-Soft-White,-12-pack-.product.100329428.html

Costco should really stop selling them.

 

[soulcougher73]

I've had good luck with the Philips brand LED lightbulbs from Home Depot. They sometimes go on sale for like < $10 for a 4 pk. I like em so far. Can't tell the difference between those and regular bulbs.

This is what i did throughout my whole house. Bulbs work great.

 

[DCal430]

M

I am so ready for the switch!

Tired of waiting for my kitchen CFL to get reasonably bright, I went to Costco last week and bought a box of ten 9.5w 800 lumen "daylight" bulbs ($17.99).Feit Electric, the brand. I was surprised how bright they are ("60w equivalent"). Instant on, yeah! These don't appear to be directional (recessed). Box says 15,000 hours and the warranty is for 5 years.

I wasn't sure I liked the instantly perceived very bluish tinge, though. Hmm. "Daylight." So, I went to Home Depot a few days ago and all I saw were Daylight and Soft White. They seem to be on the opposite side of the spectrum. Not sure I want Soft White either. Do they make "White"? I see that on the boxes as a possible but couldn't find any at Home Depot.
Hmm, I guess I should return mine for a refund when I hit Costco on Friday. At the same time I'll hit Home Depot and look to get some Philips LEDs. Maybe get a box of 4 Soft Whites and a box of 4 Daylights, both 60w equivalent and see which I prefer.

I find cool white about 4000K works well for Kitchens and Bathrooms. Warm white is good for bedrooms and living rooms. Daylight is usually 5000K and higher and can be a bit harsh.

 

[Rubycon]

PWM is necessary when dimming to maintain color uniformity.
For example, connecting a simple white LED to a variable DC supply you will notice a distinct color shift when the lamp is operated at lower levels.
This is very noticeable in torches and in applications where CRI is important across output levels, a simple circuit isn't enough.
RGB fixes that but adds cost and complexity.

Most consumer "light bulb" devices die an early life due to poor driver design either from excessive heat or spikes on input power.
A well made unit will have a large heat sink and proper voltage spike protection on its input. This isn't going to be cheap.

They are quite noisy as well - in the realm of radio emissions. This is why you cannot use LED (as well as CFL) in the sockets for overhead door openers. CFL would be a bad idea based on vibration and duty cycle but LED would actually be favorable for longevity. However, the RFI tends to make the opener malfunction!

 

[Imp]

I've tried out a few LED flashlights with multiple settings. Some of them do indeed strobe and I know by looking at the light through my camera. But some of them don't with the same shutter speeds so not sure if the PWM is perfectly synced with the light or they don't strobe.

 

[Red Squirrel]

I thought that all LED bulbs strobe. No? I know that all LED flashlights do. If they strobe then wouldn't the only way to dim them be to reduce the power supplied (voltage/current)?

They won't if they have a half decent power supply with decent filtering. But really cheap ones will flicker at 60hz. It's why you get that with Christmas lights, they don't bother to add any bridge rectification or filtering.

Though there's also PWM that's a totally different thing, but normally done at higher frequencies that won't be noticible, but it can potentially cause issues with certain things like sensors as mentioned.

Now I'm kinda curious if my flashlight does indeed use PWM or if it just uses a dropper resistor. Suppose one way to find out is to hook up a solar panel to my scope. 😛 Can sometimes see PWM with naked eye but really depends on the frequency. I can see projector PWM sometimes, well that's not really PWM just line scanning.

 

[agent00f]

PWM is necessary when dimming to maintain color uniformity.
For example, connecting a simple white LED to a variable DC supply you will notice a distinct color shift when the lamp is operated at lower levels.
This is very noticeable in torches and in applications where CRI is important across output levels, a simple circuit isn't enough.
RGB fixes that but adds cost and complexity.

Most consumer "light bulb" devices die an early life due to poor driver design either from excessive heat or spikes on input power.
A well made unit will have a large heat sink and proper voltage spike protection on its input. This isn't going to be cheap.

They are quite noisy as well - in the realm of radio emissions. This is why you cannot use LED (as well as CFL) in the sockets for overhead door openers. CFL would be a bad idea based on vibration and duty cycle but LED would actually be favorable for longevity. However, the RFI tends to make the opener malfunction!

I don't think this sort of power converter will emit high enough RF freq.

I've tried out a few LED flashlights with multiple settings. Some of them do indeed strobe and I know by looking at the light through my camera. But some of them don't with the same shutter speeds so not sure if the PWM is perfectly synced with the light or they don't strobe.

You only see the strobing if the sampling aliases with the pwm freq. For anything reasonable the former << latter, but there are drivers (or rather their microcontroller code) which use unnecessarily low freq for who knows why.

They won't if they have a half decent power supply with decent filtering. But really cheap ones will flicker at 60hz. It's why you get that with Christmas lights, they don't bother to add any bridge rectification or filtering.

Though there's also PWM that's a totally different thing, but normally done at higher frequencies that won't be noticible, but it can potentially cause issues with certain things like sensors as mentioned.

Now I'm kinda curious if my flashlight does indeed use PWM or if it just uses a dropper resistor. Suppose one way to find out is to hook up a solar panel to my scope. 😛 Can sometimes see PWM with naked eye but really depends on the frequency. I can see projector PWM sometimes, well that's not really PWM just line scanning.

Flashlights don't operate on AC, and at the voltages that led's are used they're going to have a modern-ish driver anyway. It's pretty easy to tell if a flashlight has some kind of converter since output will vary greatly without one.

 

[Rubycon]

I don't think this sort of power converter will emit high enough RF freq.

Yes it's significant enough that they have special bulbs for this purpose!

https://www.amazon.com/Genie-LEDB1-R-Garage-Door-Opener/dp/B01IHHVZTW

 

[Muse]

i got LED from HomeDepot. the box said 10 years warranty!
2 out of the 20 bulbs i got failed after 4 months. lol

I'm bringing my 10 FEIT LEDs back to Home Depot in a couple of days. They look alright (although the bluish tinge alarmed me at first), they are more than bright enough for my application (maybe too bright), but the protestations here about them failing are reason enough to return them. A warranty doesn't compensate for the hassle involved when the bulbs fail. I'd rather get bulbs with a high reputation for dependability.

 

[slag]

Anything above 2700k to 3000k is just too white for me. I like the yellow glow as it is softer and not harsh on the eyes. 4k is just too white and hurts to look at.