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  1. #1
    Anytime. Anywhere.
    Reputation: Travis Bickle's Avatar
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    DIY, how difficult, $$?

    I have an old BLT Firefly with a 15 watt bulb and a big, heavy 6v 8.5amp/hr lead acid battery.

    I have been considering getting a new light for a few years now but have been waiting for LED's to catch up to HID's which seems to have happened now with DiNotte and Hope.

    How difficult and expensive would it be to build something comparable to the DiNotte 600?

    Is there a faq that explains everyhing simply?

    I am not very electronically inclined and don't have access to a machine shop. I have a dremel and can follow directions though.

    Would I be better off just buying a DiNotte or Hope?
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    I got some bad ideas in my head.

  2. #2
    Spanish biker
    Reputation: msxtr's Avatar
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    Hi, to have a Here

    Greetings - Saludos

    msxtr
    Warning!!! my english is very very bad, sorry.

    Easy DIY led light1
    Easy DIY led light2

    The Beast!!!

  3. #3
    Singletrack Daydreamer
    Reputation: rockymtnway's Avatar
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    It's easy for a guy who likes puttering around with electronics and working on projects to say it's cheap and easy to homebrew, but it's not as cheap as you might wish, but probably not quite as difficult as you might think.

    Currently, Cutter has a homebrew kit to replace a MR-11 bulb with a 3 Cree LED set up. If you use Q5 LEDs and a fatman puck, I think it comes in right around $100 + shipping from Oz. If you upgrade LEDs, it can go up by $10 or more, but still, complete project cost should be in the neighborhood of $100-150, but you'll have a light that should blow most HIDs away for overall brightness. You'll also gain the flexibility to dim, from 3w to 12w, which dramatically extends battery life.

  4. #4
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    I have been reading the forums and understand that an aluminum housing is good to dissipate heat and I have 2. I have a 6v sla battery that I can use and can upgrade this later. The Cutter kit sounds like a good way to get what I'm looking for.

    How hard will it be to install the cutter kit?

    Do I need a heat sink?

    Does the kit come with everything I need?
    I got some bad ideas in my head.

  5. #5
    Singletrack Daydreamer
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    I wish I could answer that decisively, but I haven't used the Cutter kit yet. If the MR11 PC board is in contact with your housing, it should work fairly effectively at pulling the heat with it away from the LEDs. If it doesn't quite touch, dead air is one of the best insulators known to man. Personally, I'm creating my own heat plate using some 1/4" aluminum I have around the shop. You may want to consider using a copper pipe end-stop or something similar. Their heatsink seems kind of silly, since it's disappating the heat within the housing, where your regulator/driver is. If there's no contact with the housing, you're going to get heat build up inside the housing.

    I'd guess the cutter kit will take a bit of soldering, possibly a bit of tweaking with the dremel to make things fit right, but should be relatively straight forward. It looks complete, but like I said, I haven't used the kit and only just started a conversion project myself (but I've been doing homebrew for a little over a year on other forums).

  6. #6
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    Would a single LED kit require a heat sink?

    I'm thinking of converting my NR TrailRat using this kit from Cutter...
    http://www.cutter.com.au/proddetail....=cut731&cat=41

    If my math is correct, my light output will be reduced a bit (10W halogen vs. the single XR-E). But, battery life should be doubled (from 2.5 hours to 5+). That's with the NR 6V 4800mAh battery pack.

  7. #7
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    Reputation: rockymtnway's Avatar
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    That heat needs to go somewhere

    If you hold onto an LED driven at 700ma, you can do it for about 15 seconds before you'll drop it because your fingers are blistering. That heat has to go somewhere. One way or another, you need to get the heat off the back of the LED and to the outside air. Conduction (direct contact) with the housing is usually the best way.

    Think of the heat like a stream flowing into a pond. The bigger the stream, the larger spill way you need and the stronger dam you need to hold it back. A small creek can still spill over the top of the dam if you don't control the flow and direct it to where you want it to go. If you're dealing with one LED, you can use a thinner heatsink, but if it's not in contact with the housing, it's like building a dam that doesn't reach the sides of the valley... or something like that.... I'm trapped in inappropriate metaphor land and can't get back to dry land.

  8. #8
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    LOL.

    I'll take apart the housing tonight to see if there's room for a heat sink of some sort.

    I hadn't realized a single LED would get that hot (assuming it would produce similar heat as a similar output halogen).

  9. #9
    Singletrack Daydreamer
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    Well, it probably does produce about the same heat as a halogen 10w, but it's fragile little electronics with little silicon bits, not glass with a melting temperature of 1,200F. The heatsink doesn't have to be large, a 1/8" thick round aluminum (or copper-think plumbing end stops, or silver/copper-think 50 cent piece maybe?) disc that is in contact with the housing along its entire diameter should be adequate for a single LED. If you had more LEDs you'd need a thicker piece of aluminum (wider spillway for more water), but you're right, one LED shouldn't produce that much heat, it's just concentrated heat with sensitive parts.

  10. #10
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    While we're talking about this stuff... am I correct in my assumption that light output would be a bit reduced going from 10W halogen to single XRE, but with improved burn time? My project's goal is better battery life out of the pack I have (6V, 4500mAh), for nighttime commutes (I have another light for trail riding).

    The math:
    5 x 1.2 volt cells x 4.5 amp hours = 27 watt hours in the batteries
    1 x 3.5 volt led x 1 amp = 3.5 watts an hour draw
    27 / 3.5 = about 7.7 hours light theoretical - inefficiency losses = 5 hours or so?

    If I'm wrong on the burn times, then I'll need to re-think if the project is worth the effort - by the time I do the LED conversion and upgrade batteries, I'm probably better off just using what I have or buying a MiNewt X2 or similar.

  11. #11
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    It might actually be a bit brighter depending on the LED bin you get. Bins above P4 put out about 200-240 lumens at 1000ma, but you lose some to the reflector or optics efficiency. Technically, a 10w bulb puts out 160 lumens.

    I built a 3 x Seoul P4 (unknown bin, but purchased in May 2007) driven at 700ma. While this should be somewhere on the order of 480 lumens by my calculations, it's brighter and spreads more light on the trail than my TrailTech HID that is supposed to put out 550 lumens.

    It's possible your light will be brighter than your original 10w. If it's not, it should be very close. Your math works, if anything you're giving too much credit to inefficiency losses. Depending on your driver, you should expect 85-92% efficiency, but you're slightly underestimating your wattage, since the Crees draw 3.6-3.7 volts at 1000ma.

    That math would be something like 27 watt hours/3.7watts =7.3 hours x 0.85 (85% efficiency of driver (worst case scenario) = 6.2 hours. Best case scenario = 6.7 hours. However, this is all assuming your battery is putting out 27 watt hours. The only way to test that is to run it down with a 10w light on. If it lasts 2.5 hours @ 10w, then that would be 25 watt hours (estimated, because with halogens, they'll draw less juice as they die). If it lasts 2.0 hours, then you have 20 watt hours. Pretty straight forward math with a 10w bulb.

  12. #12
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    The battery pack lasts around 2.25hours, last time I checked, so it looks like I should still see close to 5 hours with the LED. Which would be great - that means I only have to charge the pack once a week, which is the goal (I've forgotten to charge the pack a few times and run out of light on the ride home. DOH!)

    I think I'm going to give this a shot.

  13. #13
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    Bonus, if you're interested. I know that I can run single or double Cree set up on a 9v battery for about 30-40 minutes. If you wire in a plug for a 9v battery (you know the ones with the snaps) to your driver, you can have a super small emergency back up battery that is good enough to get you home in a pinch. Can't do that with a 10w halogen!


    [edited because I recalled it was with a different light, not a 3 LED set up]
    Last edited by rockymtnway; 11-07-2007 at 10:20 AM.

  14. #14
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    That's a good idea. A 9V would fit fine in my saddle bag.

    How would it be wired? One + lead for each battery, and one - lead for each, all to the same spots on the driver? I assume I'd have to be careful to disconnect the 6V pack before using the 9V?

  15. #15
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    The 9v clips you can pick up at Radio Shack are simple: One red wire goes to +, one black wire goes to - on the voltage in side of your driver. The snaps on the top of the 9v battery make reversing polarity almost impossible. Yep, I wired mine straight into my driver. It works great on a single LED set up, but it's a really dim light on a triple unless you short out two of the LEDs (probably enough current, just not enough Vf). Obviously disconnect your 6v first, otherwise I'd suspect you could damage your real battery (or at the least, your 9v would be dumping energy into the nicad instead of the driver).

  16. #16
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    Hi, just like ypou, I have been interrested in building a DIY bike lamp and for +/-45$ Can I ordered everything to build a 3 x CREE XR-E P4 lamp (exept battery). Cutter has a great kit at 99$ but if you read most of the DIY threads here, you will soon understand what part and where to get them for a more reasonnable price. My problem w/ cutter is the driver, they are amazing things but at 50$ I think there are many other drivers available for less (ebay...) and there are other web sites that are a whole lot cheaper... I got my triple lens and a LED mount from cutter and the rest was from... eeee dont remember, but they're from UK and the shipping was free!

  17. #17
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    As others are chiming in, I will too... I went with the triple XR-E kit from Cutter. I did look at other options, but liked the setup of the 3 LEDs on a single board, with the driver included. The only thing I may want to change is the optics, but I won't know for sure until I try it out.

    It looks like the drivers run $30-40 each (bFlex, Fatman, etc) and the optics are $3-5 each (unless you go for the single optic for a triple LED, but the total price is about the same as 3 separate ones).

    So figure approx. $30 for LEDs, $30 for driver, $10-12 for optics. You're talking about $70US for everything you need to replace your halogen light (using the same housing and battery). Yes there are cheaper drivers out there, but I like the options and features of the TaskLED drivers.

    If you browse the different DIY threads on here you'll get an idea for the various retailers to shop from.

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