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How many white leds(super bright white leds) would I need to produce the same brightness as a 60w, 240V spotlight bulb. Answered

I have a standard lamp that uses two separate 60w, 240v filament spotlight bulbs. What I want to do is convert it to using white leds or super bright white leds- one led disc to replace a bulb. What i need to know is: how many leds of this sort I would need to use on one led disk to produce the same amount of light as one of the above bulbs.


Yeah, led simply doesn't output what others do in volume, by far...but they do what they do much more efficiently.

And the candela / lumen bit is not so simple either. You'd think someone could mount say 16 on the same die? L

They've done it - dealextreme has a 12 watt bulb ('single' element = array of about 16 of them)

Others I've seen have WAY more than that - trouble is they lose efficacy with volume as heat becomes a problem.

but surely when you work out the lumens from mcd and the viewing angle it's not only giving off light in that direction is it it's giving it off in all driections but the beam is strongest at that point. or is that wrong? mdog btw thanks for your help so far guys, appreciate it ;)

See attached... It shows a 180 degree bulb and a 20 degree bulb (same applies to leds as bulbs) These numbers are made up for illustration, but follow the same rules. The two bulbs put out the same total amount of light - but a tighter beam means what beam there is - is brighter.

right ok. I can't really understand it then because on instructables many people have made led lights that are really bright but they haven't used as many as would be suggested if you converted it using the converter and then times it by however many needed.

think of it as a container of water. a typical round bulb would be a punch bowl, and a shot glass would be a spot light. obviously if you fill the shot glass to the top it would be full and thus the spotlight would be bright, but if you poured the same shot glass into the empty punch bowl its still relatively empty. that said thees people bragging about there 10w shot glasses might think there pretty full, but it still takes a lot of them to fill a punch bowl.

Yeah, I understand about that- that's a great analogy by the way. But that being the case, I'm figuring that there is no way to calculate the luminosity of LEDs when used as a spotlight, therefore no credible way of working out how many LEDs I would need to achieve a certain number of lumens. Is that correct?

here is a calculator to assist with the math, just put the angle of the beam in degrees ans the candelas shown on the manufacturers site. most super bright leds i have seen out there are 12000-18000 mcd (send a link if you see some rated higher).
so a 45 degree led bulb at 12000 mcd puts out less than 6 lumins, and a 18000 mcd led at 20 degrees puts out less than 2 lumens


my advise to you is to experiment. buy a solar powered garden light from walmart for $4. take the back off an old spotlight bulb that is burnt out and hollow out. tape them together. turn out the lights and see what you get.

life is an RPG you cant level up unless you get some experience!

Brightness is not luminosity!!! If you look into a laser pointer, you will be blinded by the BRIGHTNESS but if you shine a pointer thru a diffuser that makes it 'wide angle' its not very bright at all, because there is not a large volume of light. Those projects that show really bright stuff from only a few bulbs are using high-power leds, or are camera tricks. If you take a picture of a lit LED you'll 'blind' the camera and it looks bright. This does not mean that it is brighter than a 100 watt bulb that will also blind the camera. Next time you're in a store like wal-mart, check by the tills and they'll have led flashlights in the impulse buy section. look directly into the led - its bright all right. Shine it on something - its bright but only in that small beam.

this is one of the more common lay persons answer,good going

I'm not sure what you mean by good going...is that a good thing?

i know that but they claim their array of leds runs at about 10 watts or watever and gives out lots of light enough to work by/ use as a spotlight.

See my instructable (pizza box) I couldn't even venture a guess, but leds are frankly 40-90 lumens per watt (white). This is 2-10 times the efficiency of incandescent. Are they good, yes. Are they the best thing ever? possibly. Are they the solution to all lighting needs? no. The human eye is amazingly tricky at testing brightness, because we have irises on our eyes that make most lighting conditions seem the same. You can see just as well (once your eyes adjust) in daylight brightness as indoors with a few lightbulbs, as indoors with only a few candles. These are NOT the same amount of light though... :)

hokeydokey - again thats where the angle comes in... to work it backwards, a 800 lumen bulb will put out x candellas in all direction, or 'more' candellas if it's directional - but only in that direction. Candellas are intensity, lumens are volume...

...740 lumens max...not too shabs for 15 watts.

The confusion you'll encounter in the conversion is candella (mcd) (brightness) and lumens (total volume of light output).

LEDs are rated in candella - in conjunction with an angle - beyond which the brightness is half of that at 0 degrees.

Light bulbs are rated in lumens. A 60 watt incandescent puts out between 700-850 lumens.

http://led.linear1.org/lumen.wiz will calculate the luminous intensity of your particular leds.
Typical leds are 15-45 degree angle, and 'ultra bright' put out a few thousand mcd. Some stores claim in the 15candela range - but those brighter ones are simply narrower beams.

example led: http://cgi.ebay.ca/50x-5mm-White-15000mcd-LED-Lamp-Light-Free-Resistors_W0QQitemZ290322008137QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item43988a4849&_trksid=p3911.c0.m14&_trkparms=65%3A12|66%3A2|39%3A1|72%3A1215|240%3A1318|301%3A0|293%3A1|294%3A50
15000mcd @ 20 degrees = 1.2 lumens..SO

...Thats a lot of leds.

aah wait, so if wer turnin mcd which is brightness into volume of light that would be fiding out how many leds are needed to make the same volume of light (lumens) so surely what i want to do is turn the lumens of the light bulb into mcd and have as many leds it takes to add up to that to equal the BRIGHTNESS of the bulb cus we are equalling the volume of light by using that calculator. Is any of that right? mdog

its easier to work with lumens, because they are 'total'

your 60 watt bulb puts out ~700 lumens, spread evenly around almost all directions.

To create the SAME amount of brightness, in all directions, you need 700 total lumens spread in all directions. LEDs are pretty bad a 'all directions' but do quite well at '180 degrees' beam.

Again, the calculator prevails - to put out the same total amount of light you literally would need hundreds of smaller 20-30ma leds.
You can get larger 'power' leds (search for luxeon, etc)

http://www2.dealextreme.com/details.dx/sku.2394 for example puts out about 200 lumens from ONE led - they are the future of 'lighting applications'. They do cost a few bucks each however.