How to work out Lumens ?

[ljw2k]

Hi all can someone tell me how to work out what Lumens my maglight will be putting out Approx please.


3D Maglight Host
1x U2 X-ML Led ( 1045 Lumens rated )
D.> AA adapters 2 batteries in pararell 6 batteries in total ( Sanyo 2000mAh )
3A driver this one http://www.lck-led.com/p846/Constan...-5-Mode,-3.3-4.5V-Max.-3.0A/product_info.html

Also what sort of runtime would i get on the above, i did have the formular to work out runtime but formatted my pc since and lost everything all favs.

 

[xul]

If you know 'overall luminous efficiency' for your LED you know how many watts it takes. It's about 5x the efficiency of an incand. Currently 100 lumens per watt is probably high.
V x I = watts and Watt-hours = battery V x 2 A-h, depending on how your batteries are wired.
Divide to find runtime, +/- some tolerance value, probably at least +/- 20%.

"
300~320 Lumen output
- Working voltage: 3.7V
- Working current: 3.5A"
looks like 24 lumens/W.

 

[ljw2k]

Batteries are in pararell so 4000 mAh each adapter x3 ?
Working Current on high is 3A rated on the driver.
Working voltage is 3x 1.2v rated batteries ( Fully charged 1.42V each ) 3 adapters are in series so 3x1.42v = 4.26V Fully charged batteries.

The FV of the LED is 3.35V i believe .

Not sure of the efficiency of the driver but i would estimate 80%.

 

[xul]

1.2 v x 3 = 3.6v
Batteries in parallel are rare [?] but let's say 4 A-h of charge
4 A-h x 3.6 v = 14.4 W-h of energy
1045 lumens/24 [lumens/W] = 44 W of power
14.4 W-h/44 W= 0.3 hrs.
0.3 x 80% = 0.24 hrs = ~15 minutes
Does that sound right? If it is it's the best you'll do.

 

[Lampyris noctiluca]

Hi ljw, the specs for that driver indicate that its output is down to about 2A when Vin is 3.6v, so from the XML data sheet this equates to about 750lm.

 

[The_bad_Frag]

With your setup the driver is already out of regulation with full cells. I guess the LED will put out around 400-500 lumens and this makes 350-450lm OTF.

Your setup cant really be calculated because the driver is at the start already in direct drive and the runtime depends on the discharge curve of the cells.


You need at least 4 NI-MH in series to get this driver to work. You will not even get 3,6V at the driver with a 3s2p setup because of resistance in the battery holders, the spring and the switch.

When you have the setup running with a 4s2p NI-MH setup you will get around 80 minutes of runtime @ 1000lm.

 

[xul]

resistance in the battery holders, the spring and the switch.

How much contact resistance in each, ballpark?
Good relay contacts at rated current have <30 mV drop due to contact resistance at the interface, bad > 100 mV.

 

[LilKevin715]

Hi all can someone tell me how to work out what Lumens my maglight will be putting out Approx please.

Read the XM-L Datasheet...

Also what sort of runtime would i get on the above, i did have the formular to work out runtime but formatted my pc since and lost everything all favs.

You asked about this already..., see your old thread

 

[yazovyet]

xul:
"1045 lumens/24 [lumens/W] = 44 W of power"
where did you get 24 lumens per watt? the X-ML should be over near/over 100 lumens per watt

 

[Justin Case]

Hi all can someone tell me how to work out what Lumens my maglight will be putting out Approx please.

Try using the CPF Google search at the top of the page. How hard is it to enter a search phrase such as "how to calculate lumens"?

 

[xul]

xul:
"1045 lumens/24 [lumens/W] = 44 W of power"
where did you get 24 lumens per watt? the X-ML should be over near/over 100 lumens per watt

I thought it was from his own spec's, 1045 lumens and the V and I into the LED, but now I can't find it.

 

[The_bad_Frag]

How much contact resistance in each, ballpark?
Good relay contacts at rated current have <30 mV drop due to contact resistance at the interface, bad > 100 mV.

You shouldnt compare a flashlight to a relay. Relays are made for switching with very low resistance and most have silver plated contacts. The only way to measure your parasitic resistance is to measure the voltage drop at all those components on full load.

I thought it was from his own spec's, 1045 lumens and the V and I into the LED, but now I can't find it.

The datasheet of the XM-L says 1045lm @ 3,35V x 3000mA = 10,05W = 103lm/W

 

[xul]

You shouldnt compare a flashlight to a relay. Relays are made for switching with very low resistance and most have silver plated contacts. The only way to measure your parasitic resistance is to measure the voltage drop at all those components on full load.



The datasheet of the XM-L says 1045lm @ 3,35V x 3000mA = 10,05W = 103lm/W

What's ballpark resistance for a clean battery holder, spring and switch? How does the design resistance vary with rated current? Are there pass/fail limits?
(Vsource - Vload)/I should equal the total circuit R. I'd think they'd want to keep R low, less than Rint of the battery, when using high current low voltage batteries but it depends on what the customer is willing to put up with.

1045 lumens/103 [lumens/W] = ~ 10W of power
14.4 W-h/10 W= 1.4 hrs.
1.4 x 80% = 1.1 hrs

 

[The_bad_Frag]

I really cant tell you how much it will be. I guess it will be something from 0,3V to 0,6V voltage drop in the whole flashlight if you work good. I never had that type of flashlight he wanna build so I never done any measurements that I can compare to it.

But I dont see any way to get it working on full 3 A with only 3 NI-MH even if you minimize all resistance as good as you can.

 

[Justin Case]

This thread has some data on Mag switch resistance.

 

[xul]

This thread has some data on Mag switch resistance.

Thanks, I'll have to digest that one for a while.