Author Topic: Flashlight Forum's Very Own Direct Drive Calculator.  (Read 4114 times)

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Offline cjdelphi

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Flashlight Forum's Very Own Direct Drive Calculator.
« on: September 24, 2008, 06:13:21 AM »
I'm a programmer as well as flashaholic lol, So i just knocked together a little program, the only problem is I'm not sure if all the values are correct, the Lumens Per Watt, 1 site says the P4 is 100 per watt, so the calculator provides 100 l/pw for the calculations, if they're wrong please tell me what the correct value is so i can fix and update it

After finding out that you can direct drive a P7 as most Drivers only supply up to 1amp (which is only 350 ish lumens) i wanted more power so i wrote a small program to calculate direct drive values.




How to use, simply select the bin from the left hand side, it's only a 2 hour job so i'm expecting some of the values to be wrong, you can also edit the values from the little boxes on the right, what i'm going to add next is a slider bar and an option to put in the type of battery you use along with runtimes, but until i sort out the lumens per watt, it's not going to be perfect.

Enjoy..

Even though i wrote it and i know it's trojan/virus free, always make sure to virus scan it / use online scanning websites.

Dedicated to this website a progam which calculates how many lumens you get directly from a battery, also it contains a link to this site. Source code available if you want it....

if anyone wants to try it.


http://daynacc.com/DirectDrive.zip   :thumbup:

Offline PoliceScannerMan

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Re: Flashlight Forum's Very Own Direct Drive Calculator.
« Reply #1 on: September 30, 2008, 01:23:09 AM »
Awesome!  Thanks for sharing. :)
Proud member of "The Bulk Crowd".
-PSM

Offline nemul

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Re: Flashlight Forum's Very Own Direct Drive Calculator.
« Reply #2 on: September 30, 2008, 10:29:57 PM »
cool.. thanks!
nemul

Offline HarryN

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Re: Flashlight Forum's Very Own Direct Drive Calculator.
« Reply #3 on: October 19, 2008, 02:00:13 AM »
Thank you for posting your calculator program.  I have not tried it yet, but these are always helpful.

I am curious - how do account for the variation in Vf from LED to LED in your calculator ?  I know you can buy Vf specific LED bins from Lumileds, but I have not seen this from Cree or SS.

In direct drive (and resistored) mode, the LED Vf plays a very large role in determining current and output.  I actually am a big fan of a well conceived resistored light, balanced between the battery discharge curve, the LED Vf vs current curve, the Vf vs temperature curve, and perhaps some light resistance values to moderate just a tad.  I just don't see a way to do this without the LED Vf though.  Do you have some concepts in mind on this ?

I built a light like this for a Lux V, and it took a long time to (manually) engineer these details.  I had decided to add an "in series" reverse protection diode in case the cells were accidentally reversed as well, so that adds another voltage vs current curve to the mix.   If your program could take into account these additional details, especially as they pertain to Vf curves and battery discharge curves, that would be just amazingly useful.

 

Offline cjdelphi

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Re: Flashlight Forum's Very Own Direct Drive Calculator.
« Reply #4 on: October 21, 2008, 11:12:52 AM »
I downloaded the PDF document files directly from cree/ssc and then trawled google looking for how many lumens/pwatt you get from the LED and did the calculation on that, going by my own experience what you get differs from the program as the program relies on "theory" like a 900 lumen SSC P7 giving 900 lumens it might happen for 1 in a million, 0 - 60mph top speed what's claimed and what's given is never 100% so it's just a guide line.

Offline cjdelphi

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Re: Flashlight Forum's Very Own Direct Drive Calculator.
« Reply #5 on: October 21, 2008, 11:16:08 AM »
Yes, the voltage curve etc etc yes something i have in mind, another problem is the fact that the more current the watts/lumen falls, an LED driven at 300ma might give 90lpw 900ma and it becomes 85lpw and so on something else the program does not take into account (yet)