Lumen comparison

[rescue15]

I have seen the pictures adn was wondering what teh comparisons were. I am told a 50 watt MR16 halogen bulb will get you 1000 lumen

What will 3 CREE XR-E LED's get you?

Are they at least 500 lumen? If not, how close to 500 (preff 700 Lumen) can I come using the CREE XR-E LED's (up to 5 led's)

Steve

 

[coflynn]

Hello,

It depends on the 'bin' you get. Assuming you use DealExtreme: $6.52 Cree XR-E Q5 Emitter on Premium Star (228LM at 1A) for example, they spec:

* 350mA: 107~114lm
* 700mA: 171.2~182.4lm
* 1000mA: 214 ~ 228lm

So if you can drive them at 800-1000 mA, five would give you around 1000 lumens.

BTW you might look into a 'Romisen RC-T6' as a starting point to modify (see Romisen RC-T6 Teardown & Mod - CandlePowerForums). They have six emitters, which you could drive at lower current to run them at a higher efficiency.

But that depends on what you might already have or have planned!

-Colin

 

[rescue15]

Cool, Thanks alot. At that configuration, 3 would get me around 600 lumen right?

What driver would you use to power them" I will probably be using a 12v 5aH battery pack.

steve

 

[coflynn]

If you are running all the LEDs in series, you may run into almost a voltage limit. The forward voltage is 3.7V of the LEDs, so 3 will need around 11.1V. Which means from a 12V supply you'll pretty much need a 'Boost' regulator, which are a little more expensive at higher currents...

If you can up your battery to something like 14.4V or more, you could use the 'BuckPuck' devices. See BuckPuck 1000mA DC LED Driver (PCB Mount) [3021-D-I-1000] - they are quite well built, pretty cheap, and have a reasonable amount of features! Including a control voltage input.

Or you can use something from dealextreme, do a search for 'regulated circuit board'. You'll find most are designed for lower input voltages though I suspect! Be sure to check people's reviews to see how reliable they are....

They tend to have multiple modes, so you only need a single power switch. You switch modes by turning it on & off quickly.

-Colin

 

[rescue15]

Colin, You have been so helpful. If I can trouble you noce again.

If I use the 3 Q5 Led's at 1000mA, I should get close to 700 lumen which is not bad ( rather good as far as I'm concerned) I can easily do 14.4 volts and was thinking that would be better anyway. I am looking at the aluminum 3 light reflector from DX, the 3 Q5's wired in series and the BuckPuck. This should get me what I want - right? Do you think I need to add more heat sink to this configuration or should the reflector be enough? It should touch the mag light head in several places.

Here is my parts list for the light head. Is there anything else I need?
DealExtreme: $6.90 3*Cree Reflector - Smooth Aluminium (18mm x 50mm) (reflector - 1)
DealExtreme: $6.52 Cree XR-E Q5 Emitter on Premium Star (228LM at 1A) (LED's - 3)
DealExtreme: $1.31 52mm x 1.8mm Glass Lens (glass lense - 2)
03023-D-N-1000 (BuckPuck - 1)
I already modified my D cell mag light and am getting the gaskets tomorrow.

I really appreciate the help.

Steve

 

[coflynn]

Hard to say for sure on the heat issue! Since you are in the water it will probably be OK... try to maximize surface contact though. The driver doesn't know about the LED temps, which means you'll have to be careful it doesn't get too hot.

I'd use some either some thermal paste or thermal epoxy (depending how you want to mount the LEDs) between the reflector and the LED stars. You'll have around 12W to dissipate, which isn't insane considering how much metal should be around!

To be honest there isn't a lot of point in adding more heat sink, instead you're far better off getting the heat to the outside of the flashlight so the water can dissipate it.

But it's hard to say for sure of course ;-) You'll have to experiment and see...

 

[bronk]

I went with 3 of the R2 bin Crees and the same reflector running at 930 mA. So far I have not had the ability to do a true lumen measure. However subjective data from our recent trip to Bonaire with several night dives and down to the Hilma Hooker:
Significantly brighter than the 10W DIve RIte HIDs
Same beam central spread as the 6 degree HIDs
Only brighter light (somewhat) was a 21W DiveRIte focussed way down (narrower spot).

We now have several guys looking at doing conversions / replacements of their HID lights.

 

[tharg]

hello i just put together .3 q5 with the buckpack driver. and was planing to use a 12v 5000ml nimh pack . so you are saying thats not a good idea.wen the battery loses charge it well drop down below 11.1 volts . and the light will go off. please correct me if im wrong.

 

[coflynn]

The BuckPuck specs that the input voltage should be 2V higher than the output voltage. So you could run into trouble right away...

It's dependant on the forward voltage of the LEDs though, which will vary a bit. If you've already built it you might as well test & see how bright it is!

The easiest test is to measure the current through the LEDs. It should stay constant as the battery drops, when the current starts to drop off you know the BuckPuck can no longer deliver the output voltage...

Lacking a current meter, just test with a higher input voltage of suitable current rating, and compare the brightness with your battery pack.

The LEDs shouldn't cut out completely though! You'll just be missing out on a lot of potential brightness...

-Colin

 

[tharg]

thanks i have not orderd a battery yet but the canister is built. ill try to find a 14.4v that well fit my canister. thanks for the help