# DIY - 500 Trail Lumens - 50 Bucks! + Tech Talk



## sdnative (Aug 10, 2008)

Brace for impact ...this is long!!

Ok, so I realize this isn't the highest tech, bleeding edge DIY LED light out there (my next may be), but, this satisfies my need to share my creation and all this writing will help those looking around at the options and weighing cost vs. performance &#8230; or those even wondering about the more technical DIY side of things.

Last time I checked, the industry bike lighting standard MR11 halogen's run about $3 each. In comparison, the new high output LED's aren't exactly cheap! As most you know, the biggest benefit of LED comes from the smaller size, ultra white output, and surprisingly low power consumption (generally half of a halogen), as LED's convert more of that electrical current into light. So by using an LED you get better trail illumination and even lighten your battery pack as you get to significantly downsize power requirements &#8230;just think, no more fricken cage mount brick to lug around! Unfortunately this benefit will cost you some $.

FYI, 500 lumens is plenty of light, if your DIY project directs the light optimally. This light replaced both my 10 & 15 watt niterider with light to spare!

*Basic Build Info:*
LED: Luxeon Rebel LED's on a Endor Luxeon Star base, 570 Lumens @ 1000ma

Lens: 25 Degree lens (it's too wide for my style of riding, but is a great bar mounted flood)

Cover: Old CPU heat sink trimmed down and modified, MR16 bulb reflector cover (I broke/ground the base off an old track lighting halogen bulb)

Power: 12 Volt battery, made of 10 NiMh AA's I had kicking around in various things. 1000 ma Buckpuck, Dimmable version. 3 position - Full Power / Half Power / Off - toggle switch

Mounting: The switch and light mounts the bar on either side of the stem using zip ties. Cheeeaaap (kinda like the ziiiiiip noise). Anyway, ya, so, Metal to Metal contact on the light heat sink and handle bar allows heat to flow into the handlebar, dramatically decreasing the light temperature. The battery fits in the bottle cage and I Velcro that in.

*Bill of Materials:*
-LED array, $18.50 
-Rebel 25Deg Lens, $5 
-BuckPuck $16 
-Battery Clips, $3.50
-Batteries & 'Dumb' Charger ~ $20, I had one already I bought at Frys (www.all-battery.com is a source, as well as others)
- Old CPU heatsink and misc other&#8230; Free
-Shipping, Taxes & Misc, Approx $7

Total = 50 ($70 if with new charger and batteries)

*The good stuff now: The more technical topics for those inclined to actually read em (shame on you for considering skipping this!)*

*On the topic of Electricity and Batteries:*

The Buckpuck, which is a constant current source used to drive the LED at an precise current (most you know this), has a voltage drop across it of ~2 volts (~ means approximately). The LED array needs ~9.6 V per the manufacture spec, so I figured a 12 volt battery pack (although right at the minimum) would be sufficient (9.6+2<12 volts). I realized at the 1 amp drive current, the actual running voltage may be higher, so actual measurement would be needed to confirm my battery pack was big enough. FYI, It's always better to have more voltage available than needed.

I used single NiMh's, as they are much more energy dense than NiCad. While not quite as powerful as LiIon given a weight/size, they're very cheap and readily available (And I can still use them in other elec things vs. a battery pack). I could almost get away with using AAA, I'll explain why later. Each AA cell puts out 1.2V (under load) so to get my 12 volts, I put 10 AA's in series.

Rubber meets the road: I measured ~13.5 Volts across the battery under load, which was more than the 12 Volts I expected. Good! (&#8230; in the back of my head I wondered how much this may drop after an hour or two). I then measured the voltage across the LED array while lit at 1000ma. It was 12.2V, which was higher than the manufactures spec sheets suggested! Doh! (Wait, this means the *actual Buckpuck drop was 1.3 Volts!*) Not shocking, but made me concerned that light output would drop as the batteries drained slightly and started running at a lower voltage. The Buckpuck would be forced to drive the LED's at a lower current because the input source voltage would not be high enough.

Technically, my battery was not going to provide enough volts. I needed to add 1 or 2 more AA's to my array to bump up the voltage slightly if I wanted to run be sure about running at 1 amp. But, in reality, the light was still running very bright, and the light output was not noticeably different running at 800 or 1000 ma. So, I decided to proceeded into real life trials &#8230;trails &#8230; and run at full power, and deal with a slight dimming as the batteries drained, instead of buying more batteries for my prototype.

Battery Life: So now some basic math. Yawn 

Power (Watts) = Voltage x Amperage
And, the LED runs a measured 12.2 volts @ 1 amp
Therefore watts follows as: 12.2 Volts x 1 amp = 12.2 Watts; *@ 1 amp, the light is a 12.2 Watt device*

This math is approximate! 
My batteries are 2500maH (Milli-amps x Hour), wired in series so this is NOT additive&#8230; therefore I get [email protected] volts
Battery life is a follows: (2500 Milli-amps x Hour )/ 1000 ma = 2.5 Hours.

Now, taking into account the Buckpuck consumes some power to output this 1000ma, we adjust the figure. For ~90% Efficiency, battery life becomes &#8230; 2.5 Hours x 0.90 = *2.25 Hours*. (I could have also knocked down the 2500maH to 2250maH)

So what about using AAA's? 900mAH x .090 = 810maH, @ 1 amp this give me only 50 minutes burn. If I drop down to 700ma drive current, I can run for ~1hour 10 Minutes. May not be enough light, or burn time, but wow an array of AAA's is tiny and light!!

*Theoretical Lumen Output*
Based on the manufacture LED specs (Normalized Current vs. Flux curves @ 25 C), expected LED out will be 145 @ 700ma, and 190 @ 1000ma, for each LED. Therefore, the total of the 3X Rebel array at 1 AMP is as follows: Lumens = 190 x 3 = *570lu*.

Worth mentioning is that this number is "Empirically Normalized", meaning, they measured a bunch of LED's and used statistics to find the likely output of others in the same BIN / production run, IE, My LED's. My light may put out slightly more or slightly less light than this normalized figure. *No one ever knows the exact lumen output unless they have the ability to actual measure it!* &#8230;. I don't &#8230;. this takes specialized equipment, and honestly, comparing it side by side to another light is way mo betta!

Considering a real world loss, like the 85-90% Lens efficiency, this 570 approaches *500 lumens real (well, ok, theoretical) light output*. Also, FYI, there are two other major ones to consider 1) this output number will become smaller if the light runs hot, as LED light output rapidly decreases as the die temperature increases. 2) If you use a reflector or another glass cover, etc, this will reflect light backward and decrease this output more.

*Construction Notes:*

I used 18 Ga copper wire. Copper is a lot easier to solder than aluminum, not to mention more conductive, and I had some kicking around. 24 Ga is good enough, but looks to skinny for me to be comfortable. If you're running longer wire, use the thicker gage, as it has less resistance (therefore lower power loss) given our drive currents. This is a tiny loss however for a few feet.

I also stripped the wire down (cut some strands out) at the led to make the wire thinner and easier to solder to the tiny led leads. Because the wire is filled with solder, the thinness really isn't a concern.

My base is a heat sink I sawed square and rounded off to make it look cleaner. Per the manufacture design recommendations, my fin area is more than adequate. Led's don't require much, it's something like 3 times the star footprint area. Also worth mention, is that the fins are oriented vertical, so natural convection will take its course. Essentially, this means that as the fins get hot, and a temperature differential exists across the bottom and top, air will naturally flow in the cooler bottom, and out the hotter top. This is good engineering practice, and will ensure the light runs cool, even if I decide to stop and drink a beer for 15 minutes on the side of the trail. Still reading? Just checking.

I cut to identical chucks of heatsink, and drilled a hole though them fastening with thumb screws. Essentially this created a hinge.

I used a halogen bulb reflector for a couple reasons. 1st was to keep out dust, second was because when I was first playing with this led, it sure seemed like light was going in every direction, as well as leaking from the base. I figured this needed to be re-directed fwd. Later, I tested this theory using my camera, and found there is not a difference in light output between using this reflector, having no cap at all, or a simple enclosed end cap. It wasn't doing much.

*Final Notes & Comments:*
If you use a bulb cover like I did, paint it so the bulb exterior so light doesn't leak out the back and annoy or blind you! Check out how it bleeds out the base in the pictures.

Check out the light comparison pics below, not bad ehhh. I am still searching for a 15 / 20 degree lens, 25 is too wide for a single beam setup. Actually, if the lens actually projected at the advertised 25 degrees, it might be ok &#8230;.I measured and then calculated the bean spread, and arrived at over 50 degrees!!! Let me repeat, *my 25 degree lens actually was a 50 deg lens!* What the hell, did their lens engineer forget to double his calcs somewhere?

Check out the low exposure pattern I posted. Where by underexposing the picture, the triangular (3 pattern) of each led became apparent. *I need this pattern rotated*; to take advantage of the pattern ....so, the bottom led shines right along the trail, and the other two project to the sides. This should help make the light more effective!

*Lense vs. reflectors*
1) Reflectors are used for bulbs because bulbs radiate light in every direction. They are not effective for focusing LED's (exception would be side emitting LED's I suppose), since most the light radiates forward. And vise versa holds true; lenses are not very effective for bulbs.

Reflectors (aluminum film) are at max ~95% eff, where a lens at max is ~90%. Sooo, both have generally comparable losses, but when you realize that a reflector also needs a flat lens cover of some type, which also absorbs and reflects some light backwards, at least the 5%, the numbers become truly close.

2) Reflectors are prone to making light distortions, rings, halos, and hot spots, and do a generally pretty poor job of producing a precision tight beam on top of that. A lens on the other hand can make a very tight spot, or a very wide spread, and can be designed to perfectly fade from center with utmost precision.

*Some light comparisons attached:* 
All settings are the same, so shots are directly comparable. The first is my light @ 5' and underexposed. Subsequent in order are my 10Watt 3000k halogen, 15Watt niterider cyclops, 10+15Watt side by side, then My LED light. First pics are taken at 10 feet, ISO 100, 2 F2.8 The second string of 15 ft shots are also posted.

Dam this was a long write-up. I'm sure I missed a few minor things. Enjoy!!


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## dsut4392 (Mar 9, 2007)

Nice write up, as you say it looks like a great flood to bar mount.


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## .40AET (Jun 7, 2007)

Have you run it for 20 minutes yet? How hot does it get?


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## Jim Z in VT (Sep 9, 2007)

Cool idea using an MR-16 bulb as the housing. You must have ground quite a bit off the back to get the EndorStar optic in.

JZ


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## BBW (Feb 25, 2004)

beautiful beam!!!!!! awesome for the bars; like the color too:thumbsup:


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## hootsmon (Feb 7, 2008)

Great light, and a super newbie-friendly write-up. Well done!


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## KSF666 (Mar 5, 2006)

Nice Hookah.


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## sean916 (Dec 28, 2007)

SDNATIVE I fully dig it! The buck puck pdf as I recall said that the led(s) could be 18" away from the buckpuck (if I recall correctly, I am sure someone will correct me if I am wrong) I wonder why more people don't build with this configuration... you got my wheels spinning. Would it be possible to see a close up pic of the whole unit or some sketches. Very Cool Thanks!


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## BBW (Feb 25, 2004)

KSF666 said:


> Nice Hookah.


Do you know *sdnative*?


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## Wombat (Jan 25, 2004)

Great housing idea. I'd like to see details on how you attach this to the bar mount.

Thanks

Tim


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## sbstumpy (Jul 2, 2006)

Cool design.

What did you use to make the switch/buckpuck case? How did you make the radii for the light mount and case to sit on your stem?

Thanks


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## yetibetty (Dec 24, 2007)

sean916 said:


> SDNATIVE I fully dig it! The buck puck pdf as I recall said that the led(s) could be 18" away from the buckpuck (if I recall correctly, I am sure someone will correct me if I am wrong) I wonder why more people don't build with this configuration... you got my wheels spinning. Would it be possible to see a close up pic of the whole unit or some sketches. Very Cool Thanks!


Sorry sean, but the buck puck can be up to 18" from the battery but should be 6"or less from the LED.


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## sean916 (Dec 28, 2007)

yetibetty said:


> Sorry sean, but the buck puck can be up to 18" from the battery but should be 6"or less from the LED.


Thanks Yetibetty :thumbsup:


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## racerdave (May 12, 2007)

BBW said:


> Do you know *sdnative*?


I don't know if he knows him or not, but I scrolled up to look at the pics again and just look for yourself... on the far left.


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## sxr-racer (Nov 17, 2005)

racerdave said:


> I don't know if he knows him or not, but I scrolled up to look at the pics again and just look for yourself... on the far left.


ok, I am lost.........


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## sdnative (Aug 10, 2008)

sean916 said:


> SDNATIVE I fully dig it! The buck puck pdf as I recall said that the led(s) could be 18" away from the buckpuck (if I recall correctly, I am sure someone will correct me if I am wrong) I wonder why more people don't build with this configuration... you got my wheels spinning. Would it be possible to see a close up pic of the whole unit or some sketches. Very Cool Thanks!


:thumbsup:

I have some stuff at work on the computer I can post later. I actually did a solid models of the base and a end cap I was planning to turn up but never got around to making once I found the mr16 bulb, so I have a dimensioned set of drawings I can post. Will try to do that next week.

They want the drive side wiring less than 18", because a couple things start happening. 1) Resistance in the wire eats up current.... so, now the 1000ma that the LED is supposed to be getting now, is only 950ma (this is a total guess). I could figure it out ...but betting it's small, and not a huge deal.... especially if you use thicker, less resistive wire.
2) Capacitance in the longer wire starts messing up the feedback circuit in the constant current circuitry... this is why they want you to us a capacitor across the line if you use more than 18". This works to suppress any line resonance, and thereby tighten up circuit response. Extremely long wires could start strobbing a little I suppose... not sure how extreme this is however.

My buckpuck is only about 6" away.

I would have put it in the battery pack, and think next time I will ...despite the "don't exceed 18" comments from the manufacturer. IN any case, from cage to bar is only about 20 inches max.


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## sdnative (Aug 10, 2008)

KSF666 said:


> Nice Hookah.


lol ...It is too! Straight from Egypt from a trip a couple years ago. Sheesha, only gets the tobacco these days though. BUbble buBBle


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## sdnative (Aug 10, 2008)

I've used this light on several rides now. Longest was just over 2 hours. Still 100% bright and very cool... almost feels like the light wasn't even on, cold to the touch. This was bar mounted, ithere was cool night air, and I was moving. My 15w halogen would have easily burned me under the same conditions. 

In about 10 minutes, if it is not bar mounted, sitting on the table ...it gets pretty hot. I would be concerned using it for too long like this, as it does seem to get continually hotter ...and not leveling off.

The bar, metal to metal, really makes a difference I think.


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## sdnative (Aug 10, 2008)

Thanks, appreciate that! Took a while for sure to write, but think it can help a bunch of people out there wading though all the info. At some point there will be a narrowed optic out there for this array, and hopefully I can end up with only 1 bar mounted light!


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## sdnative (Aug 10, 2008)

JimZinVT said:


> Cool idea using an MR-16 bulb as the housing. You must have ground quite a bit off the back to get the EndorStar optic in.
> 
> JZ


Ya, I needed about an inch diameter. Was a pain to do, but ended up pretty clean considering. Luckily for me I had a grinder ...with a diamond wheel. For those out there reading, it would probably be advisable to use a glass cutter (diamond or roller) to scribe/crack around the base, and then bust the base off. But ....like I mentioned in the writeup, the improvement in light output really wasn't noticeable at all. Disappointing considering the effort it took. But at least looks clean and fully protects the led & lens assembly.

Sorry, think I responded to the wrong msg. Anyone know who to delete a post?


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## sdnative (Aug 10, 2008)

Wombat said:


> Great housing idea. I'd like to see details on how you attach this to the bar mount.
> 
> Thanks
> 
> Tim


Actually pretty simple and effective ...really stays on there as the inside of my mount is a little rough. A zip tie goes right through the middle of the fins ...right through the gap. In one of the pictures I have a white twistie tie running where the zip goes.

Will post it actually mounted, next time it's on my bike. The switch ends up right above my left thumb, so super easy to dim if a rider is coming the other way, and I feel like being nice. Otherwise, I can guarantee he is seeing light spots for the next five minutes
! :eekster:


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## sdnative (Aug 10, 2008)

sbstumpy said:


> Cool design.
> 
> What did you use to make the switch/buckpuck case? How did you make the radii for the light mount and case to sit on your stem?
> 
> Thanks


Well, I went overboard and used a CNC mill in our shop to make it from black delrin. But, I'm sure there are some creative people out there who may be able to think of something better and can suggest it.

The buckpuck is kinda big, so the inside needed to be 1 inch Sq, and about 1.75 deep to hold everything. Probably a better solution DIY solution out there.

For the radius, I must again admit I used a mill with a 1" cutter to make it.... but, I could have had the same result with a radiused metal file. As, most are flat on one side and have a radius on the other ... you would need a vise to scurely hold this while you filed away though.

Search for hand files a the below....

http://www.mcmaster.com/ made for people like us DIY'ers

or go BIG http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200328621_200328621


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## sdnative (Aug 10, 2008)

thanks! ..tried to explain as much as possible. As an engineer I often am over the top on topics like this. 

All reading, can clarify more if there are other questions floating around on what I posted


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## sdnative (Aug 10, 2008)

Mounted Pics ...don't forget your blowout priced hot pink zip ties!


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## musikfan (Apr 12, 2007)

I like the "watertight" Shure microphone bag on the cage.

sweet - you a musician? sound guy?


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## sdnative (Aug 10, 2008)

Pretty primo bag huh! but ...not very water tight. That is me being bitter about my Shure mic somehow vanishing and an empty bag being in it's place. What the hell, holds a battery pack pretty good! Sob Sob... 

Used to be in a rock band in college. Have all the leftover gear too.... to bad all the lead guitar skills didn't stick around with em!

Are you a musik fan too? ..lol


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## musikfan (Apr 12, 2007)

I guess, you could say I am...
was a sound engineer for almost 20 years.....
been there done that as they say.
presidents, metal bands, country bands, all the up and coming or down and going.
anyone that was going to be someone or now is nobody.
wish I had a video camera in my head, to play it all back or make a movie.

that light of yours is pretty sweet though - let's just say you were going to sell it or had to make another one, what would you charge?


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## sdnative (Aug 10, 2008)

weird new mtbr forum layouts ...confused if this is posting correct.

Rock on! Never was in the music scene much ...got swallowed up with using my college degree to become a post grad working bee, often felt like one in the cubes they try to jam workers i at tech companies. Anyway, at least there's some fun stuff to do while living the 9-5.

Ya would consider selling it at this point ...but only cause I want to make a dual head mounted set for both mtb and dirtbike trail use. Could put the funds into that project. $ for this one would be pretty modest. Costs + a little labor. But not even close to the hours I actually have into it. PM me that ...if you haven't already


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## b1umb0y (Feb 28, 2005)

First off, beautiful write-up and great design!

I have been reading about soldering LEDs and the warning concerning the LEDs sensitivity to heat. 

Do you have any recommendations for safely soldering the wires to the LED leads?

Thanks,
bb


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## sdnative (Aug 10, 2008)

Thanks! Appreciate that. I took a hell of a long time to write up, and at first was pretty bummed cause there was absolutely no responses, comments or anything! So thanks :thumbsup: 

If the led is mounted to a star, most the heat from the iron will flow into the star base, so overheating for the most part isn't a huge concern ....unless you leave the iron sitting on the star for minutes. That said I do have some suggestions learned through experience over the years.

1) Use copper wire, aluminum is a pain to solder when you're dealing with sensitive and delicate soldering
2) If you are using larger gage, strip the wire at the solder end down to a smaller gage. IE, I was using 18 gage, but stripped the solder end down to approx. 24 gage. 24 G is pretty small. (This may seem like a skinny wire, but, it isn't a concern however since the solder in the wire will help conduct and the seemingly small gage therefore isn't really small!)
3) Strip back about 1/4 inches at the and and pre-solder the wire the wire before even considering getting to the 'solder to the star' stage. Make sure it's covered, but doesn't have a blob on the end.
4) Cut this back so only a small piece is left, only a little longer than the solder pad on the star base.
5) Presolder the mount pads on the star
6) Don't use any more solder, just put the wire on the star pad, and just touch the wire long enough for the sodler to melt.
7) pull iron off, cool, and inspect to make sure it's totally soldered.

Done, and minimum heat or hassle!! 


FYI, I am working on a new light that should be done within the month. It will be about 2X the output and at possibly a lower price! I plan to make a couple extra and put them up for sale also.

Thanks ~Chris


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## b1umb0y (Feb 28, 2005)

Excellent! I have actually something similar to that before, so I know exactly what you are talking about. Thanks again for a great write-up.

---bb


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## basketcase (Apr 21, 2008)

sdnative said:


> FYI, I am working on a new light that should be done within the month. It will be about 2X the output and at possibly a lower price! I plan to make a couple extra and put them up for sale also.
> 
> Thanks ~Chris


HECK! Luv the write up. when I get a little cash, going to try this out, as I need something. VERY interested in your next cheaper project.

Jonathan


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## snowhoss (Feb 18, 2007)

Awesome thread, not sure why it doesn't have more hits! Superb design and write-up. I only wish I had half the skill and creativity that you have. Keep us all posted on any other projects.

James


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## rusellg2000 (Oct 6, 2008)

Well done sdnative, fantastic write up.

I myself was in a similar position a few weeks ago and trying to find all the info I needed in one place was a total nightmare!

I have slowly collated all the stuff I need to get me started, just waiting for the parts and equipment to arrive. 

I just wish I found your thread sooner. All good info there and I love a thread with pictures. The time you have spent compiling your write up is certainly appreciated.

In fact, I'm gonna bookmark it for future info!!


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## p97z (Dec 19, 2006)

Excellent write up!

Looks like an awesome flood...


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## Greparm (Apr 4, 2008)

Great light! Can you get a lens that is more of a spot for use on the road?


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## Jim Z in VT (Sep 9, 2007)

It looks like on your hi/low/off switch you used adjustable pots instead of plain resistors? Cool idea, lets you fine-tune the brightness levels? Do you have any links or specifics on those?

JZ


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## sdnative (Aug 10, 2008)

Unfortunately, after contacting the manufacture of this 3X array, the answer was no. They have no plans to make a tighter spot lens either. This was a bummer ...but it wasn't a total loss, as other lenses may be adaptable if I modify a base with the correct focusig spacing.

I also learned that when most manufactures state their angle, they are actually talking half angles. So this means the actual 50 deg I measured was correct, and they meant it to be a 50, not a 25! Learned the hard way. However when they state FWHM this is the actual angle, and doubling doesn't come into play. Explained here. http://en.wikipedia.org/wiki/FWHM

Thanks for the comments!


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## sdnative (Aug 10, 2008)

Let me dig through my notes. Think I used adjustable 5K linear pots ...the current is sooo low that I could get away with the little dinky micro watt pots normally used on audio signals. I have 3 pages of math and drawings. Looks like I measured [email protected] ~2K Ohms, and [email protected] when I had the two resistors running in parallel (1K Ohm effective).

It was essential to use adjustables vs. resistors, because the relation between input voltage and output current was totally weird. I did the math of what the manufacture said would be the output at a given input voltage, but the real life ended up totally different. Kind of annoying actually!! The pots let me tune the brightness to exactly what I wanted at full as well as half too.

Will post a schematic asap.


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## sdnative (Aug 10, 2008)

*Switch Schematic*

I used a 3 position mini switch. Up was (half power), Middle (Full), Down (Off). Pots are mini 5K Ohm audio signal PCB mount type.  I used a 0.1 Ohm, 1%, 1 watt resistor in series with the LED to measure the actual ouput current. By putting a volt meter across this resistor, and having it set to mV, I was able to read the current/10. IE, 80 mV = 800 mA. Cool  Using a small resistor is better, as a larger one (like a 1 Ohm), lets you directly read the actual current, but affects the circuit too much. Schematic below.


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## sdnative (Aug 10, 2008)

FYI, have a new way to calculate battery life; using Watt Hours vs. Amp Hours. It is MUCH more accurate, and will help give a very realistic burn time when using BUCK / BOOST circuits. You'll out there should be substitute your own numbers and be able to use my math as a framework! Will post asap. ~C


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## Jim Z in VT (Sep 9, 2007)

SD, thanks for the switch/resistor info and schematic! I'd like to try something similar with a light I'll be building over the winter....hoping to do a 3-way lo/med/hi with off being "pull the plug", or maybe off/lo/med/hi with a small rotary switch, if such a thing even exists.....I haven't started looking for switches yet. LEDs, optics, drivers, connectors are beginning to arrive in my mailbox from DX (sooo slow, luckily I'm in no hurry!)

I don't suppose the spacing of the 3 LEDs on that star match up with any of the triple 35mm optics out there? (DX and Cutter sell them). I wonder if there's a focusing lens that could be layed over the flood optic you have, to tighten up the beam? Just a thought. It looks like an awesome LED, too bad there's not more options. Great flood for a bar-mounted light though!

JZ


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## sdnative (Aug 10, 2008)

If you're using most of the newer NiMh and LiIo batteries out there, once you get up to the drive voltage (12, 14.4 etc) there is so much excess power avail, having various settings starts seeming like a little of a waste of time to me. To many bells and whistles. I myself only dim because of other riders coming the other way. 

Rotaries are often kinda bulky. May not fit in a small light body.

My next will be a full-to-half(ish) power push button, and a 'pull the plug' off. As long as I get 2+ hours at full I'm happy! 

Waiting on DX to, soooooo, slooooow.

I'm hoping to mod a few of the DX MCE lenses I get to see if I can get them to work with my Endor Rebel. Will post the findings. @ 18 this is still an ok option for most people, if the lense is a little tighter. 500 lu is a lot of light after all!! But 1000 is better


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## ocean breathes salty (Oct 1, 2006)

sdnative said:


>


Hi SD.... awesome little thread you are developing here.. Keep up the good work!:thumbsup:

I can't get my head around your circuit diagram.... I think something is amiss?

Your schematic at the top shows centre off... but that would have the current passing through the 1k resistor so:

position C will be off as there is a path without going through any resistors

position B will be the highest as it is the path with most resistance i.e 1 Kohm

position A will be a slightly lower beam as 1/r=1/2+1/1 r=1/1.5 r=0.66 kohm

please correct me if i am wrong but i wired it up just to double check myself and mine came out as above.

i had another way to wire it up bookmarked here at post #7. It is slightly more complex but definitely gives centre off.


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## mdsjack (Oct 26, 2007)

sdnative said:


> I used a 3 position mini switch. Up was (half power), Middle (Full), Down (Off). Pots are mini 5K Ohm audio signal PCB mount type. I used a 0.1 Ohm, 1%, 1 watt resistor in series with the LED to measure the actual ouput current. By putting a volt meter across this resistor, and having it set to mV, I was able to read the current/10. IE, 80 mV = 800 mA. Cool  Using a small resistor is better, as a larger one (like a 1 Ohm), lets you directly read the actual current, but affects the circuit too much. Schematic below.


Thanks, this is exactly what I wanted to do with my first diy set.
It will be useful.


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## sdnative (Aug 10, 2008)

Ya, I see the confusion. ( All those reading, ??'s, The higher the voltage at the Buck Puck 'Control, the lower the output current).

1) The On-Off-On is just the type of 3 way switch. It doesn't pertain to the way I'm using it.

2) You are correct as to the function of my circuit ...except, both of the resistors are ~2 Ohm ...so Req=1 Ohm. (Good to see another equation post btw)

For those also reading, when the switch is in position 'C' the middle resistor is still hooked into the circuit, but current flows right around it since I have a direct 0 ohm connection in parallel.

As to my choice of Low-High-off, I had it wired slightly different at first (High-Low-Off) ...but, when you are out riding and another person appears right around a corner, flipping a quick hard up on the switch is much easier than trying to switch to a 'middle low' position while bouncing around on a trail. I found myself bobbling and turning the light off many times ...frustrating and slightly embarassing. Middle high became a better choice to me for that reason.

Next time I'm just going to use a push button 'half-ish power' as that is even easier in every way.

Good questions! Love it! ~C


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## sdnative (Aug 10, 2008)

Updated the picture, should add clarity.

Also, the Volt Amp measured figures I put in are from chicken scratches I made on a note pad ...they may not be totally accurate! 

My pots may not be exactly 2K ohm either ...sorry, should have taken better notes.


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## sdnative (Aug 10, 2008)

*Better battery holder*

Mouser.com is a great source for components!! Highly recommend this great company for every DIY'er out there!

A better 10X AA holder is mouser's P/N 12BH310A-GR (which is 5 per side, back to back)$1.65, or 12BH309-GR (which is 10 in a row with solder tabs!) $2.35

They also have all the other components you could ever want to get at cheap prices too ...will try to post what I'm using for my next build as far a connectors, switches, etc, asap.

~C


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## sdnative (Aug 10, 2008)

*Battery Life: A Better estimating method*

*Battery Life: A Better estimating method*

SO&#8230;. Most people out there either Buck (drop down) or Boost (pump up) the voltage going to their LED using a high tech constant current led driver. This is preferred in comparison to a linear voltage regulator (or resistor) because the efficiency is much higher. A linear regulator just eats up the extra power it doesn't send to the LED, essentially making heat. If you are using a LR, the following discussion doesn't apply to you. Instead, just do the same as in my writeup: use total current to your LED, and divide the maH figure by it. (2500maH / 700ma = 3.57 Hrs).

BUT, for a Buck or Boost circuit, the voltage & current coming out of the battery vs. the voltage & current going into the LED are different, and this excess is not converted to heat, so the math is different! So how do you figure battery life??

Some background: That buck driver is taking in a higher voltage/lower current, and knocking it down to a lower voltage/higher current. This is a pretty efficient process, so not a lot of power gets eaten up. A boost circuit is doing the opposite, drawing higher current from that low voltage source and spitting out as a higher voltage/ lower current to the LED.

The logic: If we hope to better estimate battery life, we need to find a relation between voltage and current to more closely describe the situation. This needed link is Watts. 1Watt=1Volt x 1Amp, or, Watts is equal to Voltage multiplied by Amperage. Using a wHr, vs. aHr battery figure is our answer!

The math: Now how to convert that 2500mAh battery rating into a watt based rating. (note: 2500mAh in it's most basic definition means, the battery can put out 2500 milliamps for 1 hr)

Amp x hr x Volts = V*A*Hr (substituting W=V*A) this becomes WHr

Therefore, in english: To get a Watt Hour figure, Multiply the Amp Hour rating of the battery x the nominal voltage of the battery. Easy!

For each of my batteries: 2.500 Ah x 1.2 = 3 Watt Hours (Wh). (Note, 2500mA = 2.5 Amp)

And I have 10 batteries, so the total Watt Hours is 10 x 3 = 30 Wh (I could have also used the entire battery pack, 2.500 Ah x 12 V= 30 Wh) Works out the same.

So to find battery life of your light, just divide this Watt Hour figure by the total watts of your light, then take away some minutes for driver loss.

*For my DIY 500*: 12.2 Volts x 1 amp = 12.2 Watts; Restated, when driven at 1 amp, my light is a 12.2 Watt device

*To figure burn time*: 30 Watt*Hr / 12.2 Watts = 2.45 Hrs x 90% Efficiency = 2.21 Hours at full power.

So 2.21. I first calculated this @ 2.25 hrs in my writeup. It's basically the same for my light, which was expected since the voltage in vs out was so similar &#8230;but&#8230;..

For my new light I am driving an MCE (4 die Cree chip) @ ~14.4 volts using a Takled.com Fatman boost driver, using an 8X array of NiMH. To figure my battery life, I have to use this above equation since I have ~9.6 volts going in and ~14.4 coming out of the driver. My old math just doesn't work.

Equations applied: 

*Battery energy*: 2.500 Ahr * 9.6 V = 24 Wh

*LED power*: Watts=Volts*Amps (@ LED); W=14.4volts*0.8 amps =11.52 Watts

*Battery life* is, 24 Wh / 11.52 Watts = 2.0833 Hrs * 0.80 (80 % efficiency) = 1.67 Hrs 

So, as long as my batteries are good ones and delivering the advertised mAh (they are good quality) I should be getting at least my required 1.5 Hours of max power trail burn.

Perfect!:thumbsup:

Questions? Post your specs/ calcs if this :madman: is you!


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## ocean breathes salty (Oct 1, 2006)

sdnative said:


> For my new light I am driving an MCE (4 die Cree chip) @ ~*14.4 *volts using a Takled.com Fatman boost driver, using an 8X array of NiMH.


Nice write up! Thanks for taking the time :thumbsup:

Is your Vf a measured voltage with a meter or from the data sheet? My M bins are showing about approx 12.3 Vf which is pretty consistent with what others are seeing. It would be interesting to hear if there is a little bit of a lottery with the MCE's.


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## sdnative (Aug 10, 2008)

Busted! Wait, people actually read this stuff!?! Lol... 

Nope didn't measure a MCE; still anxiously waiting for a pack of 5 I ordered a while ago. Kinda did the math with the worst case. Planning for a massive heat sink and overdrive also, so will be a little higher too. 

Will post once I have actually measurements at various drive current. 

Hope it helps... though I realize most you guys are using LiIon, which have tons of extra power. Hence all the 3 X MCE lights running around!


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## User1 (Mar 10, 2009)

Great write up here and I liked what you accomplished too.

I'm pretty new at this building your own lighting system, but I do have a bit of a background in the what an electric bike components consist of. So I am able to follow for the most part on everything you had said.

I'm wondering a bit about the switch. It seems a kinda bulky for such a simple switch, or am I missing something here?


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## TheBigYin (Sep 29, 2008)

Holy Thread Revival Batman 


The big black lump on the handlebars is a case that holds the actual switch, a couple of variable resistors and the actual driver that runs the led (buckpuck) - I wouldn't imagine that there is a great deal of space in there, after all that little lot is slotted in.


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## sdnative (Aug 10, 2008)

User1 said:


> Great write up ..... I'm wondering a bit about the switch. It seems a kinda bulky for such a simple switch, or am I missing something here?


Hey, a blast from the past ...this poor light has long since been put in the desk drawer and replaced by 3 others, but doesn't mean the DIY has changed any right!

My "bulky switch" (which, ya, is kinda bulky) contains the led driver as well as some adjustable micro pots for adjusting the dimming levels (Hi/Med). This buckpuck is quite a big little cube (as far as led drivers go). So, fitting an almost 1" cube somewhere is a pain, but it has to go somewhere! I suggest putting it with the battery pack for any future builds (don't worry too much about the wire length, but use thicker wire, I use 18GA to lower resistance)

The micro switch itself is tiny!

For your DIY light: A higher performing option in the same $50 pricepoint, I would suggest you go with the Cree MCE led, the Boom SS reflector, and a 4 pack of LiIon (from dealextreme, this charger) going through the 700ma buckpuck. DX also sells some battery holder cases that you can fashion into a battery box, look on mtbr for the 18650 LiIon holder thread. Go with the unprotected LiIon's, as the voltage dropout of the LED will keep you from ever overdraining the LiIons' (the led output dies before the batteries drop below 3 volts) This makes for a VERY nice bar mounted, idiot proof setup that puts out ~700-800 Lu! A little like one of my other lights.

Good luck! :thumbsup:


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## sdnative (Aug 10, 2008)

wow ....blast from the past. My first real plunge into true diy. LOL, what a sad little beam that is. Outdated info, but good circuit stuff for beginners. Since it took me hours and hours to write this, felt like I could justify resurfacing it one last time before it drifts away for ever ...and ever...


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