Peter, ARC4 levels

Through various posts by you, and sometimes stating numbers from Henry, I get the following:

Level 1 = ~600mA (at which the ARC4 is ~9.3 lm/W or about 30% efficient)

Then you said the current drops down to 0.707 of what the previous level is. So:


Level 2 0.6A(same as 600mA) * 0.707 = 424.2 mA

Level 3 is 424.2mA * 0.707 = 299.9094 mA

Level 4 is 299.9094mA * 0.707 = 212.0359458 mA

Level 5 is 212.0359458mA * 0.707= 149.9094136806 mA
(at which the ARC has risen up to ~90% efficient)

Is this correct?

As much as I read out of the manuals, the drop of 0.7 regards to the brightness, not to the input current, it will not be linear at the higher levels.
And the current draw depends on the input voltage and the LED. The LEDs have some tolerance, so an efficient LED may result in an input current of 800mA at 3V and a lesser one will have 1.2A (for example).
Hook up your Arc4 to an variable power supply and check it (hey, wouldn't it be nice to have a tailpiece with two wires instead of a CR123 cell?)

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NewBie said:
(at which the ARC4 is ~9.3 lm/W or about 30% efficient)



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Your 30% efficiency figure is way too low. That 9.3 lm/W was a worst case value for lumens exiting the light. I don't see any way that you can get from there to your 30% efficiency value.

This is not input current levels PeLu. This is based on output current levels delivered to the LED.

PeLu, in a current controlled regulator, output current doesn't change based on LED Vf.

To go a little deeper, these are average current levels delivered to the LED, where I do believe the ARC4 is in reality, PWM adjusted for brightness, and not current regulated. In my designs at work, I utilize a mix of both to achieve a 1:10,000,000 dimming range at a very low cost.

The reason I say this is due to the strobe effects folks mention when the flashlight is dimmed, and some of the photos they have taken to show this, when they move the ARC4, or are themselves moving.

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NewBie said:
This is not input current levels PeLu. This is based on output current levels delivered to the LED.


[/ QUOTE ] Sorry, I misunderstood that, I always thought about input current.
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PeLu, in a current controlled regulator, output current doesn't change based on LED Vf.

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It is said that the Arc4 is not current regulated, it is power regulated instead. It is claimed that this is the next step (I thought for 20 years that driving a LED with constant current is just perfect). Whatever it makes for a difference.

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In my designs at work, I utilize a mix of both to achieve a 1:10,000,000 dimming range at a very low cost.

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Wonderful! You can do that without any visible flicker?

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Doug S said:
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NewBie said:
(at which the ARC4 is ~9.3 lm/W or about 30% efficient)



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Your 30% efficiency figure is way too low. That 9.3 lm/W was a worst case value for lumens exiting the light. I don't see any way that you can get from there to your 30% efficiency value.

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Which did I say was 30% efficient? Is not the end goal, the about of light exiting the flashlight?

Certain batches of luxeons are now 30-35 lm/W. Lower output than this can be lowered by 8% with a non-AR coated lens placed in front of a luxeon, up to 30% loss with aluminum reflectors (assuming all the light hit the reflector, which it doesn't), and even heating of the luxeon die, above 25C die temp will cause lumen output drop (conversely, cooling the die below 25C causes an increase in light output).

Now Doug, we do know that an average of 2.4W is delivered to the LED at level 1, from Peter's statements. He also said Level 1 is an average of 600mA delivered to the LED. Additionally, high brightness binned Lux III can reach 85-95 Lumens at 700mA, where a T bin cuts Lux III off at 87.4 Lumens. Running at 600mA results in about 85% of this. Or, 74.29 Lumens.

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Gransee said: Everyone who has a back order for an Arc4+ will get the new 33 lumen units.


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33lumens / 74 lumens = 44%

Next:

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Gransee said: This keeps all the units below the 1.25amp @3volt test.


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So, 3 V * 1.25A = 3.75 Watts going into the flashlight.

Most my Luxeon I or Luxeon III have a Vf of 3.75V at 1A, and about 3.6V at 700mA. I have some that have a Vf of 3.5 at 600mA and some that have a Vf of 3.7 at 600mA. So, lets take an average. Peter is down at 600mA to the Luxeon, so 0.6A * 3.6 = 2.16 W to the Luxeon.

2.16W / 3.75W = 0.576, or 57.6% electrical conversion efficiency at Level 1.

Then you take the 44% Lumen efficiency.

0.576 * 0.44 = 0.25344 or 25.3% overall ARC4 electrical to Lumen efficiency.

Another way of looking at it, is 74 lumens at 600mA for a Luxeon with the die at 25C. The ARC4 is 33 lumens though.
So, we take 33 lumens with 3.75W into the ARC4.

33 Lumens / 3.75 Watts = 8.8 Lumens per watt.

Now, to get real we need to know the input current level and voltage. To nail it down, we'd additionally need to measure the output current and voltage.

With nearly every other flashlight, shortly after it is introduced, CPF members take and make efficiency measurements quite soon. I've yet to see these charts for the ARC4, which is quite odd, and a rather rare occurance.

Strange.

NewBie = Jarhead ?

/ubbthreads/images/graemlins/thinking.gif

Klaus

Maybe if Klaus = Klaus /ubbthreads/images/graemlins/wink.gif
Sincerely, I have no idea /ubbthreads/images/graemlins/thinking.gif

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FrenchyLed said:
Maybe if Klaus = Klaus /ubbthreads/images/graemlins/wink.gif
Sincerely, I have no idea /ubbthreads/images/graemlins/thinking.gif

[/ QUOTE ]

ROFLMAO

The Arc4 introduces some new concepts to flashlights like brightness calibration. To achieve a certain brightness range, the current to the LED will vary over a wide range from unit to unit whereas the brightness will vary by a much smaller amount. As a result, actual light output is a more accurate indicator of performance than the current to the LED.

I understand that some people are wanting to compare current regulated lights to the Arc4. I recommend measuring the output in an integrating sphere to get the most accurate numbers possible. Simply manipulating current (which I mentioned in an earlier post as ball park figures) numbers will generate a bogus result.

Peter

Peter, would you call it truly bogus, or would it be more likely ballpark???

Also, heat generated by a flashlight is also a direct indication of efficiency. Flashlight A and B put out the same lumens. Flashlight A makes twice the heat, thus Flashlight A is less efficient.

Secondly, you have said your lights are brightness calibrated. 33 lumens is the spec, you set them at 35 lumens for a fudge factor. So, if I measure input current and voltage (multiply the two together to get watts), since you did the brightness calibration, then I get X Watts in, and 33-35 lumens out. Then if I take 34 lumens (call it average), such that 34 lumens/ X Watts = Y lumens per watt, correct?