edison type led bulbs

Please forgive me if this question has been posted elswere, or if this belongs in a different subject. but does anyone have any idea how to make a led light that can be screwed into a standard american 120v light fixture? preferably with at least 8 leds, or even better, a Luxeon Star!?

You need like 40 Leds or a converter of sorts. Putting even a Luxeon Star in will fry it unless you have the proper resistors etc. Also, incandesents don't care about reverse polarity but LEDs don't care for it...in other words, your LED will flicker on and off at 60 hz, but maybe that doen't bug you.

I recently posted a similar question and, after evaluating all the current options, decited not to conquer the project.

There is something in the works from that wonderul electronics whiz Dat2Zip, but it's not ready...not now at least.

Rothrandir, several companies are already working on drop-in replacements for incandescents using luxeon stars and 5mm LEDs.

For 5mm-based lamps, one of the most notable ones is LEDtronics, who actually manufacture LEDs themselves too. They have them in all sorts of form factors (eg. MR16s, edisons, PARs...etc), but I'm not sure if they've taken care of polarity (which is fairly easy to take care of using a bridge rectifier). They have developed these LED bulbs to work on line voltages like 110/120VAC or 220/230/240VAC, so you can use them almost wherever.

There are also quite a few developing Luxeon-based lamps, like Lumidrives (who have been somewhat quiet) and aussie company, MyShowers.

Unfortunately, its early days yet, and I have not seen LED-based replacements that will rival the output of their incandescent counterparts yet, although the gap is closing. Take the average 11W PL bulb (in edison-base form) for example - it averages at least 90 lumens/watt for a total of 990 lumens from that lamp. That's more light than an M6! You'd need a lot of 5W(120 lumens @) before you could match that output.

Originally posted by Rothrandir:
Please forgive me if this question has been posted elswere, or if this belongs in a different subject. but does anyone have any idea how to make a led light that can be screwed into a standard american 120v light fixture? preferably with at least 8 leds, or even better, a Luxeon Star!?

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<font size="2" face="Verdana, Arial">You can always use a current-limiting resistor to limit the current flowing to the LED.

. . Vs-Va
R=-----
. . I

R = Resistance (W)
Vs = Source Voltage (V)
Va = LED Voltage (V)
I = LED current (A)

That will limit the amount of current going into the LED on the positive side of the sine wave. Since a LED is a diode, the LED will be off on the negative swing of the wave.

As another poster has pointed out, the LED will flicker at 60 hz if you do it this way. You can alleviate that problem by using a capacitor to smooth out the pulses.

Your bulb will also be real dim since LED's don't put out nearly as much light as an incandescent bulb.

Also, after you build your bulb and you go to Home Depot and see a regular halogen bulb that puts out 50 watts of light, is just as efficient as the LED and only costs $1, it will seem amazing by comparison.

There are several companies marketting comnplete LED mains powered bulbs with very impressive claims. The main proponents of this industry are LEDtronics Inc, The LED Light.com and Solar GB.
One of these companies markets a direct replacement for filament bulbs called DecorLED. The bulb is pear shaped like a conventional incandescant, but is made of polycarbonate and contains a AC to Dc converter and a tree of LED's. They only supply the bulbs im industrial quantities (Boxes of 10 minimum, and the bulbs are about $34.00 each.) Being polycarbonate the bulbs are pracically indestructable and are insensitive to vibration and general mechanical abuse (such as festoons of bulbs hanging on cables). The bulbs are available in all LED colours including several shades of white.
The other type of LED bulb I've seen is marketted by Solar GB. These bulbs resemble Philips' SL Compact Fluorescent bulbs in appearance and contain hundreds of LED emitters. The claimed output is that of an equivalent sized SL but with a 100000 hour lifetime, rrather than 8000 for an SL. Prices are also very high at this time, bit if you do the maths for both types of bulb over the 100000 hour lifetime the LED bulb is cheaper to run. They base this pricing on the electricity consumed by the 100 filament bulbs an LED bulb would replace, the replacement of those 100 bulbs and the labour costs involved in actually changing those bulbs... thinking on an industrial basis... it soon adds up! I suspect if you've got a festoon of 1000 bulbs that are on 365 days a year in all weathers, the intial outlay really makes sense!

thank you for your prompt and informational replies, i had hope for a simple answer, but it appears there is none unless i shell out some money that i don't have. well, it looks like i might as well forget the idea at this time and try again in several months, considering the rapid evolution in led technologys, mayb waiting would be the best answer anyway. thank you once again.

"You can always use a current-limiting resistor to limit the current flowing to the LED."

suppose you use 1 3.5V white LED at 20mA.
R = (120VRMS - 3.6V)/20ma
R = 5.8KOhm.

The power dissipated by the resistor will be:
P = I x I x R
P = .02 x .02 x 5820
P = 2.328 Watts...thats a big resistor.

"That will limit the amount of current going into the LED on the positive side of the sine wave. Since a LED is a diode, the LED will be off on the negative swing of the wave."

However, an LED is NOT a rectifier diode and can't withstand such a high reverse voltage.

"...the LED will flicker at 60 hz if you do it this way. You can alleviate that problem by using a capacitor to smooth out the pulses."

You would need to add a rectifier to it and a capacitor, rated at a very high voltage. Rectified and filtered 120VRMS produces about 180VDC.

Originally posted by lux0:
[QBHowever, an LED is NOT a rectifier diode and can't withstand such a high reverse voltage.
[/QB]

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<font size="2" face="Verdana, Arial">Yeah, you'd need a big resistor.

It surely wouldn't be practical in any way, I was just trying to point out that it could be done.

That's why I said that after designing a LED light the incandescent would seem amazing by comparison in its efficiency and light output.

"Yeah, you'd need a big resistor. "

a resistor won't reduce the reverse voltage, it's open circuit voltage, remember.

"BTW, I think you could get away with it without using a rectifier. "

Then you'd rely on the LED being a rectifier, and they're not designed for that. I predict it would work fo 8.33mS (1 half cycle)

Originally posted by lux0:
"BTW, I think you could get away with it without using a rectifier. "

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<font size="2" face="Verdana, Arial">I deleted that, I was thinking of a full bridge rectifier.

You could make it work. It's not impossible. There's always people out there who will be naysayers. Sure, it won't be efficient or very effective, but if having a LED lightbulb is what floats this guy's boat, it can be done. Where's there's a will there's a way.

"It's not impossible"

i never said it wasn't...it just won't work or be safe at all without a rectifier and a more efficient means of limiting the current.

Originally posted by luxO:
"It's not impossible"

i never said it wasn't...it just won't work or be safe at all without a rectifier and a more efficient means of limiting the current.

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<font size="2" face="Verdana, Arial">Your posts seem to go against what a support group is for. While I'm trying my best to help the guy out, you're just busy trying to shoot down what others say. Be more positive. He didn't ask for his ideas to be shot down, try helping him out a little.

There's nothing more annoying than being on a group and having one guy constantly nit-picking the others and shooting down their ideas for help.

Your next post would be much more appreciated if it isn't aimed at shooting down my comments, but instead aimed at helping the original poster out.

Thanks.

How about using a tiny mains transformer, such as the one found within a shaver charging circuit. Solder the input of this to your BC or ES cap (In England you used to be able to buy bulb-cap -shaped plugs that you could wire small mains appliances to, that would plug into a standard bulbholder). Then use a full wave rectifier and a smoothing capcitor to conition the circuit. Dependant on the voltage and current ratings of the transformer circuit, you could then have a series-parallel matrix of LED's, each row adding up to the supply voltage. In experience I have found adequate light from 4 Nichia cyans to light a room well enough to read from itsr eflected light, so a matrix of 16 LED's pointed upwards at either a white cieling or some kind of reflector device should give good lighting.
A home-made table-lamp needn't have any mains wiring at all...just design the lamp to run off the output of a "wall-wart". This is probably he safest way to run LED's off the mains. This is something I intend to do after my visit to America with some outdoor LED arrays I want to mount on the outside of my home. The mains supply will power a 4.5V dc supply and thhe connections to my lamps will be made using simple bell-wire or phone cable. No dangerous high voltage circuits to leak, get wet and short out!

Marshall, I think you are overlooking an important point here. It's not just about all possible solutions, it's about safe solutions...
Re-reading this thread, keeping this in mind, I for one can't see where LuxO is going against what a support group is for...
Not exactly sure who is nit-picking here.

Careful everyone...watch out for other peoples toes...

Originally posted by *BlackBart*:
Marshall, I think you are overlooking an important point here. It's not just about all possible solutions, it's about safe solutions...

Re-reading this thread, keeping this in mind, I for one can't see where LuxO is going against what a support group is for...
Not exactly sure who is nit-picking here.

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<font size="2" face="Verdana, Arial">I am looking at it in the overall sense that the original poster tried to ask for help making a LED light bulb and I offered my help. Lux0, instead of offering constructive criticism and correcting me in order to help the poster build what he wanted to build, he just gave plain criticism and didn't do anything to help the poster at all.

For instance- if you gave someone advice and I didn't agree with it, constructive criticism would be "You're on the right track, but I think in order to get it to work correctly you'd have to do this...."

On the other hand if I just said "Your idea won't work. It's more involved than that" and didn't offer any alternative advise, then that's just plain criticism and didn't really help you out.

I hope you can see what I mean.

How efficient are those wall warts? Seems like a simple enough solution.

re: the LEDs being reverse-biased - just wire up two strings of LEDs, 40 "forward" and 40 "reverse" and that problem is gone. All of the reverse current will flow thru the reverse string. You'll still have a 60hz flicker but it will have a higher duty cycle since you've got light on the negative half wave as well as the positive. (Or would that make it a 120hz flicker? I guess so.) Smoothing cap is still a good idea, but there's no real need for a rectifier. The two LED strings themselves could be thought of as a rectifier configuration, but that's not really important.

It should make for an interesting experiement using caps. I wonder if it can be made smooth enough such that flicker is totally eliminated - those LED transient on/off times are much faster than glowing incandescent filaments. Insufficient "capping" may not cause flicker per se, but likely more of a "throb", which is probably annoying as well. I've hooked up 3-4 luxeons in series and put them thru a regular 12V transformer (for halogens) and the flicker is pretty darn awful to the point of being unusable. For reference, a 3 ampere rated full bridge-rectifier costs only $0.25, not sure how much a good cap would cost though. Any one got an idea?

Rothrandir and others.
Yes it is very easy to do. For more than 4 LED's the best is to use a bridge rectifier. Only other components you will need are 2 caps, 2 resistors and a fuse. You will need to make a small circuit board epoxyed into the neck of a broken light bulb from where you get the 120v and the LED cluster attached appropriately.

Email me directly for further details.

the idea does seem to have some worth after all, however, i know very little about electronics, and was hoping mainly for some well written instructions and possibly a diagram or two. although i am pleased that this topic has gotten people thinking about it. and hopefully all of you knowlegable people out there can figure something useful out, while i sit at the sidelines and wish i had the know-how and talant that you do.