Flashlight bodies/general knowledge questions

[zeramant86]

I'm relatively new to led flashlights, but I've got a couple of questions if you guys don't mind helping me out. I'd really like to play around and build a few as much as my skills will allow. I've gotten a few of the guys at work to agree to help me out in the machine shop if need be. Unfortunately, I can't use the EDM to make the housing because it is booked for like 3 months. I'd originally planned on doing that with a tri-bore then lathing the rest.

First are there many places other than dealextreme, lighthound, gizmograb, and kaidomain to purchase host bodies for flashlights? Of these which would be the best price/quality? (preferably with tactical switch)

Alright, just some general knowledge questions.

1) The combined battery Vf must be higher than the Vf of the Led, right?

2) What is the calculation for battery life, I know it uses driver efficiency etc.?

?? Life= (Battery current X Number batteries X Driver efficiency)/(Driver rate) ??​

3) A dumb one, the driver only regulates current and operates within V parameters, right? So is there a seperate board needed for multiple modes?

4) What gauge wire should be used for connections between the led and battery? Should this wire be copper?

5) I know for heatsinks, copper, gold, and silver are ideal, but practically what is the best option? I'm sure shelf copper isn't pure, would a chunk of aluminum work also?

http://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html
​

6) I'm not sure if this is the same, is thermal compound the same stuff used for CPU/heatsink connections?

7) Can Li-Ion batteries be hooked up in multiple serial/parallel combinations?
(example using 2200mA: 2x18650 in series -+-+ with 3 sets in parallel [total 6 batt.] = approx. 7.4V @ 6600mA)

http://s278.photobucket.com/albums/kk85/37604/?action=view&current=Drawing1-Model.jpg
​

8) Does anyone make holders for this sort of thing? I've seen some on here somewhere once before made out of white high density plastic. Is this only a custom item, or is it sold online anywhere?

Thanks in advance

 

[Kestrel]

You're trying to cover a huge variety of questions in your thread, just so you know. I would very much recommend using the 'search' function for each of your topics independently. Many of your questions have been covered rather extensively in the applicable CPF subforums.

----------

5) I know for heatsinks, copper, gold, and silver are ideal, but practically what is the best option? I'm sure shelf copper isn't pure, would a chunk of aluminum work also?

Using CPF's search function with the keywords 'heatsink aluminum brass copper silver', one of the many many returns is a chart I wrote up a while back:

Thermal Specific _Den _"Thermal
conduct HeatCap _sity _volume"
(W / mK) (J / gK) (g/cc)_ (J/ccK)
​

Aluminum 250 __0.85 ___2.7__ 2.3
Brass..... 110 __0.38 ___8.6 __3.2
Copper... 400 __0.39___ 9.0__ 3.5
Silver..... 430 __0.23 __10.5 __2.4

"Thermal volume" is for a fixed-size part – i.e. an internally-mounted heatsink. For example, a 1 cubic centimeter brass part requires 3.2 joules of heat to raise it by 1 degree Kelvin (or Celsius).

Although brass is a good choice for a heatsink in this application, aluminum is also competitive (as its heat capacity per unit weight is over double that of brass), and about one third the weight - think EDC. It will absorb almost 3/4 of the heat compared to a brass part of the same volume per degree rise in temperature, but will also conduct heat away from the emitter over twice as fast as brass will [...], except that the aluminum heatsink would be only 1/3 the weight.

Pure copper would be an excellent choice, except for the fact that it is considerably more expensive than aluminum and much more difficult to machine, from what I've heard.

----------

Again, what you are asking about in this thread is a huge breadth of knowledge, and I wouldn't recommend tackling this without doing substantial searching and reducing your queries a fair bit. My two lumens,

 

[gcbryan]

1) The combined battery Vf must be higher than the Vf of the Led, right?

Direct drive-yes, using a boost driver-no..otherwise there would be no (1) AA led flashlights.

2) What is the calculation for battery life, I know it uses driver efficiency etc.?

(battery voltage x capacity)/ (emitter vf * current ) and reduce this number by driver efficiency. That's an approximation.

3) A dumb one, the driver only regulates current and operates within V parameters, right? So is there a separate board needed for multiple modes?

There are many kinds of drivers.

4) What gauge wire should be used for connections between the led and battery? Should this wire be copper?

I believe 22 awg - 28 awg would work but it depends on the current it's being driven at.

6) I'm not sure if this is the same, is thermal compound the same stuff used for CPU/heatsink connections?

Yes.

7) Can Li-Ion batteries be hooked up in multiple serial/parallel combinations?
(example using 2200mA: 2x18650 in series -+-+ with 3 sets in parallel [total 6 batt.] = approx. 7.4V @ 6600mA)

Yes.


I've only answered some questions and I've just given simple answers. You need to do more research as mentioned.

 

[zeramant86]

Just to make sure I'm getting this, you're saying essentially that aluminum transfers heat faster than brass, but that it also raises temp much quicker, due to the same reason? Which I guess would mean that It would have a lower limit on runtime for a highpowered led...?

I've been browsing the forums for awhile, the amount of info. seems to be a bit overwhelming. I've caught bits and pieces, but I haven't seen a start to finish guide that explains the full process. I'm just trying to fill in the blanks as best I can.

Thanks for the help, and if you guys know of any threads, sites, etc. that could help a noob feel free to link them.

I'd like to start with something simple for my first light, like XPG series in a midsize EDC. I'll probably use aluminum for the heatsink, because we've got tons laying around at work.

 

[^Gurthang]

Z,

Have you looked at the M@G mod threads? You can get a lot of your questions answered if you study some of the MANY threads covering; single emitter, multi-emitter, drivers, battery packs, heatsinks, reflectors, etc. etc. etc. Its how I got started learning what it all means.

 

[kosPap]

Kestrel, nice post and data....

care to inlude properties of SS and Ti as well?

 

[Kestrel]

Kestrel, nice post and data....
care to inlude properties of SS and Ti as well?

Thanks, no problem, I'll get add those when I have a moment.
I put that chart together because of all the times I see folks post about thermal conductivity like it's the end-all be-all, but ignore specific heat capacity & density (showing that silver is a relatively poor choice, for example). And don't even get me started on diamond/copper composite. <thumbs down>