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)?
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)?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.
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).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)?
I am so ready for the switch!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.
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 thought Costco only sold the best but the FEIT bulbs from Costco are crap. Many of mine have died in less than a year.
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.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 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.
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."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)...
The ones I bought there are. Non dimmable and brighter then the ones/60 watt bulbs, they are supposed to replace too.Anybody know if the Walmart LED's are any good?
This is about as close to a compliment as you can get from 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.
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.
This is about as close to a compliment as you can get from slag.
Slag must be really loving them LED A9's.
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.
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 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)?
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'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.
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.
I don't think this sort of power converter will emit high enough RF freq.
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.i got LED from HomeDepot. the box said 10 years warranty!
2 out of the 20 bulbs i got failed after 4 months. lol