Total newbie, struggling with electronic basic concepts

[kurni]

First of all, many thanks to Charles and ViReN, who had been very helpful and patient with my questions. I have a few more questions that are more general, so I address the forum; I thought this way others might also benefit from the my learnings.

I have read many posts, but I am still confused because my electronic knowledge is next to nothing. I don't want to purchase any multimeter because my wife will go berserk, but I cannot stand the itch to mod my Fenix E1 and M@g 6D so I have to give this a go based on theory.

1. How do I turn on a Cree Q5 safely and easily? jtr1962 seems to imply that Q5 can be operated between 2.74v and 3.64v safely assuming proper heatsink, so I am guessing that direct driving 2x1.5v from 2 D alks would be safe. What I don't understand is how many mA Q5 would draw from the alks. I know that P=VI but that doesn't answer how many mA for 3v because I don't know how many W. Download implies that alks would provide 500mA while NiMH would provide 1000mA, but he used MaxFlex and I just want to understand the basics at the moment, so I'm trying to minimise the variable: just Q5 and a pair of D alks in series without any driver.
2. How much V and I does Fenix E1 provide the LED? I'm sure that it would safely turn on a Q5, but I am curious.
3. I am sure that Fenix E1 would underdrive the Q5 from Erasmus, so would the tint be bluer than the current Rigel? The spec said WC is pure white, but would it still be pure white if driven by Fenix E1? I understand that WC bin still represents a bracket of spectrum, so I just want to know about the average of the bin.
4. Would the Q5 be more efficient than the Rigel? I mean, would it be brighter if I replace the LED with a Q5?

I have more questions but they depend on my first question. I am hoping to use Fenix E1 again as my expectation significantly raised after using P2D RB100; I hate the blue tint and if I can get at least the same brightness, I would proceed with E1 mod. With my 6D M@g I want a LED mod; I haven't seen anything better mod than the Multi-Sink by Download (suggestions are welcome) with MaxFlex. Actually, here goes more questions:

1. Which one is brighter, 1 Q5 at 1000mA or 5 Q5 at 350mA. I am guessing that the 2nd configuration is brighter because the lm/W at 350mA is higher than 1000mA but I don't know if 5 emitters means 5 times brighter.
2. Which one is more efficient, 1 Q5 at 1000mA or 5 Q5 at 350mA. Actually I don't really care with efficiency as 6D is plenty, but I'm just curious.
3. Download said that 5 Q5 at 1000mA would turn my 6D M@g to a hotrod, so how many mA would drive my the mod reasonably until my new alks are depleted under not so "high ambient temperatures" (thanks Fenix for the can of worms :duh2?

That's all for now, thank you very much for reading. I have searched the forums, if somehow I missed extensive discussion in other threads, please kindly point me to them.

 

[yellow]

first of all, current and output ramps up not equally with a led.
With 2 cells and no circuit, the led might light a bit, but nothing more. Possibly sees 100-200 mA (but thats just a guess, can be more or less also)
You need a step-up circuit to ramp up the voltage!

On my town bike I a have a triple-cree setup that sees some 600 mA (in series connected).
When I turn my single Cree flashlight on at 1 A, the triple seems not be be switched on - so much for the "better efficiency".

with a 6D, a 5 led setup should run at some 2.5 Amps, check Your cells, deduct 20% to whatever is printed on them and divide by 2500, thats Your runtime.
A Mag-Head and body offers quite some meterial, build Yourself a massive sink out of an Aluminium plate of 1/2 " at least and this light should survive without problems.

Unfortunately You got the wrong emitters: The Cree are better than the competition for starters (and most other ppl also) because they are more rugged and less heat sensitive, but one needs Sandwisch Shoppes McR-XR reflectors to get the best results and those are expensive.

 

[ViReN]

http://www.candlepowerforums.com/vb/showthread.php?t=125280 have a look at this thread

except for luxeon III you can now use Q5 Cree's and get output of about 950 Lumens at 1 A Current.

 

[kurni]

first of all, current and output ramps up not equally with a led.
With 2 cells and no circuit, the led might light a bit, but nothing more. Possibly sees 100-200 mA (but thats just a guess, can be more or less also)
You need a step-up circuit to ramp up the voltage!

It's a rather steep learning curve for me; I'm using XR-E Q5 from Erasmus. Am I right interpreting this Vf chart that given 3.3v XR-E Q5 would attempt to draw 350mA from the battery, that's why using 2 alks in series without any circuit the LED might just light a bit? Therefore if I use 3 NiMH in series (assuming 3.6v) without any circuit, would XR-E Q5 attempt to draw between 700mA & 1000mA?

Unfortunately You got the wrong emitters: The Cree are better than the competition for starters (and most other ppl also) because they are more rugged and less heat sensitive, but one needs Sandwisch Shoppes McR-XR reflectors to get the best results and those are expensive.

XR-E Q5/WH are not the wrong emiters, are they?

Many thanks,
Kurni

 

[Doh!Nut]

No you did not get the wrong emitters, I think yellow was saying that in his opinion the best reflector for the XR-E is ~$15 one from sandwich shoppe.
I would say try the optic from KAI or DX for around a dollar, or use the standard mag reflector, it may or may not be as good but it will get you going.

You appear to have a pretty good grasp of electrical theory but dont forget you are dealing with SEMIconductors, they dont behave like a normal bulb, doubling the voltage will not simply double the current but may triple or quadrouple it. This is why there is not "Watts" figure (other than marketing speak"
The Vf chart you link to is not really a Vf chart, have a look at the Cree site at the XR-E darta sheet and you will find a graph of typical Current vs Voltage, for standard electronics (a resistor) that would be a straight line but it is not, a small change in voltage gives a big change in current. combine this with the fact that a 1.2v nicad may start at 1.4v and be depleted at 1.0 v and there is no way you will get a consistent output from your LED

There was a thread a while ago about a 2D mag using a micropuck, a nice little mod at a reasonable cost.

Nick

 

[kurni]

Thank you kenster for dropping me a PM with an elaborate explanation, and everybody who has helped me in this thread. I learned that even though XR-E are specified to have typical Vf 3.3v at 350mA, each XR-E can have a very different Vf at a given mA. Now it makes sense why people prefer lower Vf because P=VI, hence lower Vf would yield lower P at the same lumen bracket. Erasmus tested his Q5 in post 26 and found one that has 2.95v at 350mA, which was much more efficient than the typical Q5, wasn't it?

Am I right guessing that nFlex or bFlex adjust the voltage the LEDs need it while enforcing a given current? I would have wasted that beautiful 2.95v Q5 if I direct drive it with 3.6v NiMH in series, because the beauty would draw more than 350mA; and nobody knows how many mA can the NiMH can provide. Like Doh!Nut mentioned above, at 3.6v the beauty might draw a lot more than 1000mA; the bottom line is that it would have died. That's where nFlex or bFlex is useful to limit the current, right?

Now I realise that it doesn't make sense to build cluster Q5 using 6 alks, does it? At 500mA continuous discharge D Energizer capacity is almost halved, so I prefer to discharge it at less than 500mA. P=VI so 4500=9*500. One Q5 driven at 1000mA typically requires 3.7v so 3700=3.7*1000. Taking into account 85% efficiency, the circuit and the LED would need 4353=3700/.85. 4500 is just slightly above 4353, so usually there is no way to drive more than one Q5 using 6 alks.

So for now I just use an nFlex to drive a Q5 with 6 D alks, when AW sells D LiIon I would be all over it. D LiIon should be OK with 5000 continuous discharge, 18500=3.7*5000*6, 94350=111000*.85, in theory it's enough power for 25 Q5 at 1000mA , but 5 Q5 is a HOTROD

Many thanks,
Kurni