Lumens vs A

[branderson1983]

I need an explanation, I am a noob.

There is so much information here, even searching is hard to sort through.

Can someone please point me in the right direction??

 

[voltctrl]

I need an explanation, I am a noob.

There is so much information here, even searching is hard to sort through.

Can someone please point me in the right direction??

Lumens versus amperes? You want a relationship between the two? It would depend heavily on the type of emitter.

Basically, ampere measures electrical current; how many electrons pass through a conductor per second.
Lumens measure brightness; how bright it makes an area, sort of. The wiki article explains it better.

 

[Cataract]

More amps = more output. Less amps = less output.

There are only 2 ways to vary their output: #1: give them less amps - either through a "driver" circuit or a resistor. The second way is with PWM - Pulse Width Modulation. Luckily, I have already written the article on that:PWM - What is it, How does it work and how to detect it.

 

[yellow]

thats new info
:thinking:
because I thought - till now - that there is no difference between any led.
no light at whatever low voltage till the point (voltage) is reached that they start to give light, then extremely more light with just tiny raise in voltage.
The only difference is, how much Ampere they can stand (3 + 5 mm ones up to 20 mA, "normal" high power ones up to 800 mA - 1 A, "high power" models more)

And "normal" 3/5 mm never could be used with varying voltage
(except for special models with IC built in - for just this application)




back to original topic:
as has already been typed: the more power (Ampere) to the led - the more output (Lumen)

lets do rough examples:
Cree XP-G (XP-G2) is the actual "normal" high power led. Nominal max current is 800 mA and it can give :thinking: ... ~ 300-400 (?) Lumen with that.
Cree XM-L (XM-L2) is the actual "high power" high power led. Nominal max is about 2.700 mA and that should be about 800-900 lumen.
... more or less ...

Now when there is a certain light in question and some data (correct data!) is given, one can calculate what current consumption that might be and with that what the output (lumen) can be.
Typical example is some cheap light, claiming 10.000 Lumen, that has "only" one XM-L led, runs on a single 18650 Li-Ion cell, with a stable output, for 3 hours.
--> total BS
;)
"10.000 Lumen" ... not possible with just one led
"3 hours on 1*18650" ... ~ 800 mA --> can "only" be 300 Lumen

understand?
;)

 

[880arm]

:welcome:

Like the others said, higher current (amps) means higher output, at least up to a point. The maximum current and amount of increase will vary by LED but the increases are not linear. That is to say that supplying double the current to a single LED will not necessarily double the output.

You can get an idea of the effect of increased current by checking out the manufacturer's datasheet for a given LED. For example, the Cree XM-L U2 has a calculated output of 416 lumens at 1A. Doubling the current to 2A results in 742 lumens, less than twice as much. Typically as the upper limit is approached, or even exceeded, the increase in heat is greater than the increase in lumens.

To see an example of this, check out the Cree XM-L datasheet. There is a table on page 3 that shows the calculated luminous flux (lumens) at selected current levels and a graph at the bottom of page 5 that shows what the curve looks like from ~0.1 to 3 amps.

Note: the numbers on the datasheet are commonly referred to as "emitter lumens" and are more of a theoretical level of output. In actual usage, the OTF (Out the front) lumens will be lower due to electrical and optical losses from the driver, window, etc.

 

[jaycyu]

y=-x^2+x
y = lumen
x = amperage

A = runtime
Lumen vs runtime

 

[Poppy]

y=-x^2+x
y = lumen
x = amperage

A = runtime
Lumen vs runtime

Someone has a strange sense of humor.

 

[Cataract]

thats new info
:thinking:
because I thought - till now - that there is no difference between any led.
no light at whatever low voltage till the point (voltage) is reached that they start to give light, then extremely more light with just tiny raise in voltage.
The only difference is, how much Ampere they can stand (3 + 5 mm ones up to 20 mA, "normal" high power ones up to 800 mA - 1 A, "high power" models more)

And "normal" 3/5 mm never could be used with varying voltage
(except for special models with IC built in - for just this application)




[...]
;)

Okay, you got me... I had about 12 beers in me last night and there was a stubborn pink elephant on my keyboard. I modified my post before everyone starts thinking I'm an idiot.