LED Bulbs

[Chris S]

Anybody have a any luck with LED lighting in the home?

I bought some LED bulbs- put one in a 6" recessed light- very white light not too bad
Put 2 in 5" recessed lights - too little light
Put a bulb in a bedside lamp- OK for reading
Put one in the porch light wall fixture not too bad.
These were 3-8 watts of light replacing 55-65 watt bulbs, so great savings, but no wheres near the Lumens
Anybody find something they really like?

Chris

 

[Valhalla]

I prefer to use CFL. They are not prefect, but you do get used to them quickly. After a while, you don't know you have them.

 

[SteveT]

The past couple of years we've used strings of LED's for outdoor Christmas lighting. They look great and the electricity savings are substantial (estimate $30 or $40 each year).

 

[Jerry_NJ]

The only LED for 115vac house bulb sockets I've found are at Walmart and are 1.5 watt (almost free electric power-wise) and claim to be 40W equivalent. They are not to my eye and the light is a "scary" white light. Still I like them for some applications, maybe for an outside "standing light" for security, not for reading. The problem I've had is the first two I purchased at Walmart failed within the first 100 hours of use. Walmart did, of course, refund my purchase price. A couple of days ago after finding the Walmart display fully stocked again I purchased another, for a light in the basement in a dark corner that I can leave on most of the time. It has been working fine so far....still waiting to see if there is an early failure.

I look forward to more, seems the first poster may have some, some at a hight light output, say 4 watts for 100 watt equivalent output. It would be nice too if the ligh color could be a little warmer.

 

[begreen]

I've tried a couple and so far am not impressed. I don't like the cold, bluish light, even for outdoor Christmas lights. For indoor use, the lumen output of the unit I got is weak, more night light level than reading level. I'd love to see this technology take off, but the light output needs to be higher, color temp warmer and the cost needs to come down a magnitude.

 

[jebatty]

They're coming, and color will get better. Local bldg supply (Menards) has LED nightlights for about $2. Great advantage is that they take very little power, are very cool running, and last almost forever. An especially good use is for the nightlight on the refrig - don't need any heat here. We only use the night lights when we have guests who can't find their way around the house in the dark as they search for the biffy. CFL's everyplace else.

 

[Corey]

I guess it really depends on what color you like. I searched high and low for CFL's that accurately reproduce a good incandescent bulb "white" without being too red or too blue. I finally found a bulb I liked, only trouble it it comes on at about 40% brightness and takes a couple minutes to warm up!

Same goes for LED's. Everyone has their own taste from blue-white to pure white down to warm white. I picked up a pack of 100 of these off ebay:

http://cgi.ebay.com/100-PC-0-5-Watt...3098859QQcmdZViewItem?_trksid=p3286.m20.l1116

Have plans to make up a couple of units possibly to install around the wood stove and or around the TV. I can usually be found around one or the other for the cold winter nights and usually have the lights dimmed pretty low for nice ambiance. I would say the color rendition in the ebay photo is pretty true to what you actually get...a nice warm white light. A single LED seems to put out about the same light as a candle. (Which may have additional use around Halloween!) Each 'LED' package is actually 5 discreet LED's in series for a 100mW current draw.

 

[jebatty]

If you buy ready-made LED lamps, they typically consist of the LED's, a bridge rectifier, and a resistor to limit current. They also can be powered by a single diode rectifier and a resistor. You can make these up yourself. You need to know the rated current, which varies by the LED chosen. Then use Ohms Law to calculate the resistor value.

 

[Jerry_NJ]

I assume an LED is forward biases and "drops" between 0.7 and 1.0 vdc when emitting light. So, if one takes 1 vdc and looks at the suggestion that at least one fixture has 5 LED in series, that accounts for approximately 5 volts. Or too small to bother with, thus pick a resister that limits the RMS (or Peak?) value of the house ac, to the desired current of the LED, perhaps 100ma. That being the case R= 120/0.1 = 1.2K would be about right, and the wattage would have to be greater 0.1 x 120 = 12 watts, this doesn't sound good, as the LED I have on hand claims to be 1.5 watts, must be the diodes use a lot less than 100ma, maybe only 10ma, that would bring the power down to 1.2 watts, about right, so the current must be around 12ma. Indeed we can computer the rms current as 1.5watt/120v = 12.5ma.

Interesting.

 

[granpajohn]

A traditional traffic light, (red, yellow, green), uses a clear incandesent bulb at each color. I think they are 120w and they come in bulk at a dirt cheap price. However, they do burn out in a very annoying way. So, traffic engineers are slowly replacing these systems with LED lights which cost over $100 each. Worth it if they don't burn out and cause crashes.

They have found that they do, in fact, fail at about a 70% rate. They don't care, because the manufacturer offers free replacement. Hopefully this will improve.

The LED systems use less power to the tune of about 10w. Varies from 8-13w depending on the color. This gives them the big advantage: They can be run on battery power, (from the cabinet), during power outages. These batteries last 4-6 hours. Best of all, since outages often last much longer than that, it is easy to send a man out to an intersection to replaced the batteries with a fresh charged set. (2-4 gel cels IIRC). Hence, the savings is in labor cost.

Took time to get these things to work, because it was difficult to get the green panel. They looked rather blue at first.

So anyway, it is very important to have a long life warranty, like Jerry_NJ did, because otherwise it can be a lot of money spent/wasted.

Oh, and, I don't think I want my family room to look like it's lit with a traffic light.

 

[jebatty]

This looks like good info on LED's:

http://www.kpsec.freeuk.com/components/led.htm

 

[DiscoInferno]

I assume an LED is forward biases and "drops" between 0.7 and 1.0 vdc when emitting light. So, if one takes 1 vdc and looks at the suggestion that at least one fixture has 5 LED in series, that accounts for approximately 5 volts. Or too small to bother with, thus pick a resister that limits the RMS (or Peak?) value of the house ac, to the desired current of the LED, perhaps 100ma. That being the case R= 120/0.1 = 1.2K would be about right, and the wattage would have to be greater 0.1 x 120 = 12 watts, this doesn't sound good, as the LED I have on hand claims to be 1.5 watts, must be the diodes use a lot less than 100ma, maybe only 10ma, that would bring the power down to 1.2 watts, about right, so the current must be around 12ma. Indeed we can computer the rms current as 1.5watt/120v = 12.5ma.

Interesting.

If you use a resistor in series with a few LEDs and power it directly with 120V as you suggest, then the vast majority of the power is going into the resistor and not the LED. Using your numbers, there's 5V across the 5 LEDs and 115V across the resistor. Since they all have the same current, this means that 115/120=96% of the power is lost as heat. For any semblance of efficiency you would need a step-down transformer or DC-DC converter before the LEDs.

 

[jebatty]

I suspect this is why you find white LED bulbs with multiple LEDs, like 18. White LED's take 4 volts x 18 = 72 volts. If a single diode is used, half wave rectifier, approximately 1/2 of line voltage is passed to the LED's, or 60 volts. No resistor needed.

 

[Jerry_NJ]

Good reference jebatty, thanks a keeper. I had no idea an LED drops 2 volts plus. I see you mention 4 volts for white. The 1.5 watt, so called 40 watt light output has something like the 18 LEDs you note. That goes a long way to increasing efficiency, but they are so efficient in any case that we can afford to wast a lot of the power in a limiting resistor to keep the package light and cheap.

Interesting too to read so many fail early, that's been my experience. I'm now on my third one trying to get one that lasts more than a week. They are suppose to las 30,000 hours, and Walmart will take them back for a refund for 90 days.

 

[RedRanger]

We have achieved a much longer life from our CFL`s after remembering to leave them on for a minimum of 20 minutes before turning them off. Big difference.! Turning them on and off frequently seems to kill-em fairly quickly. Traffic lights are mentioned in this thread, so can I assume the same rule doesn`t apply to LED`S?

 

[jebatty]

I don't think I've ever had a single LED fail, as opposed to a multiple LED lamp, of which I have none. LED's will fail quickly if they are exposed to higher than rated voltage. Perhaps voltage surges or spikes are killing them? It might be better practice to under-voltage them and provide surge/spike protection, both of which would add to the cost. Penny wise vs pound foolish?

I can't relate any of my CFL bulb failure to turning on and off frequently. I think sometimes I'm more conscious of failure of a bulb that is turned on and off frequently than I am of a bulb that is left on for longer periods of time. In all events, over the past several years the overall failure rate has been low, which I am guessing to be maybe one bulb out of 10. At the same time, we have several CFL's that have lasted more than 10 years, get lots of use, and still are going strong. I think it balances out.

 

[jebatty]

An idea for easy LED use on your electrical equipment - add a single rectifier diode and resistor and use as a pilot light. I added two to my generator, one to each side of the 240 volt line. I was having trouble with a plug connection of the generator itself that was making one line intermittent. Got very easy confirmation that both lines were hot.

I'm also going to be adding LED pilot lights to the circ pumps on my boiler. There is enough space in the wiring box to do this, and I will drill a hole in the case and just use friction to hold the LED to the case. Some circ pumps now come with an LED pilot light.

I was thinking about using an LED pilot to quickly let me know if my new 4000 watt-equivalent LED searchlight was on. LOL

 

[Jerry_NJ]

I don't have any general complaint about the life of CFL bulbs, which we have used extensively for more than 10 years. I do know that the lamps I have on timers, on at dusk, off around midnight, have the most hours on them, and the seem to just keep going. I know some of these have been in this on for about 10 hours a day for years. Yet, we do have failures, and as sonnyibc says it may be due to short on/off cycles.

I can see too how the LED 120vac fixtures I've used have such high rates of failure: 1) so many bulbs in series, just like cheap Xmas tree lights, any one fails, string goes out and 2) I had the LED bulbs in a frequently switched location (head of basement stairs).

 

[Jerry_NJ]

I've used simple "neon" lights with a resistor, no diode needed, for pilot lights. I have one on my electric timer for the hot water heater, it has been working for years, maybe 15 years, and still going strong. The long life is due in part to a high resistance resistor, picked by trial-and-error, so the light isn't very bright, but still easy to see. Yes, I like pilot lights too, on the same subject my almost new HWH (well about 6 years old) has pilot lights on the upper and lower heating elements. I do look at time from time-to-time to see if one is on.

 

[Redox]

Jim, you don't really need an additional diode; the LED already is a diode and will work on AC or DC.

Chris

 

[dvellone]

I've searched extensively for leds for quality indoor lighting and haven't come up with much. I've found some that work well for task and reading lighting - pleasing color and ample light- but I don't think that the quality area lighting is here yet. A bit more rise in fossil fuel and bit more drop in the market and those leds may just be around the corner.

 

[Jerry_NJ]

Redox, good point and works as long as the reverse breakdown voltage is high enough. Seems if a number of LEDs are in series the reverse breakdown voltages add, so no single diode has to take the full "reverse" voltage. This make the cheapo circuit simply a resistor of the right value...albeit this isn't the most efficient, but so what, the LEDs need so little current that loss in the resistor isn't large either.

The big surprise to me is that the forward voltage drop is so high, stated at 4 volts in this thread for white LEDs.

Is there any data (empirical) about how long the next most efficient, the CFL, it has to leave on before turning off if the cycle isn't to have a detrimental effect on the blub life? sonnyibc mentioned 20 minutes or something like that. If true, I'd guess they need to be on long enough to come up to full brightness. Just a guess.

 

[DiscoInferno]

What I've read says that the current crop of white LED-based lights are still less efficient than current CFLs. LEDs are usually more directional than CFLs, which means if you compare based on peak brightness rather than total light power LEDs fare better.

I think that the large forward drop in white LEDs is because they are internally composed of 2-4 different-color LEDs in series to approximate white.
Edit: It looks like phosphor-coating blue LEDs is the more common method used for white LEDs, and 3.5-4V is about right for blue LEDs.

 

[jebatty]

Jim, you don’t really need an additional diode; the LED already is a diode and will work on AC or DC.

Should have known this. I've only used LED's in low voltage situations, so the rectifier diode plus resistor is what I have done. Could also use a transformer to deal with reverse voltage breakdown, but that kind of defeats the small size advantage of the LED in a circuit.

What about, though, the result being only using 1/2 the power being supplied? Is this a PF question? Wouldn't a bridge rectifier produce approximately twice the efficiency?

 

[jebatty]

Jim, you don’t really need an additional diode; the LED already is a diode and will work on AC or DC.

Should have known this. I've only used LED's in low voltage situations, so the rectifier diode plus resistor is what I have done. Could also use a transformer to deal with reverse voltage breakdown, but that kind of defeats the small size advantage of the LED in a circuit.

What about, though, the result being only using 1/2 the power being supplied? Is this a PF question? Wouldn't a bridge rectifier produce approximately twice the efficiency?

[sorry about the double post]