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Old 10-23-07, 09:31 AM   #1
nerobro
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Doing the DIY headlight thing.

So shorter days have come. I rather enjoyed the "right after the commute" bike ride. But in my neighborhood that's asking to become street pizza.

I had just built a LED taillight for my motorcycle. That inspired me. Why not build a LED headlight?

That night I hopped on ebay, and went digging for a good deal on white LED's. I found a hundred 13,000mcd white leds for $9. Shipped.

I don't like the look of big headlights hanging off my bars. Not to mention I have narrow bars and don't have a whole lot of space to spare. My goal is to make a 90 LED headlight, that's no taller than the thickness of the handlebars. From the front it will look like I have a 8-10" wide bar of light. From the side, with the lights off, it should be hidden by the handlebars.

I'm making the circut board this week. I'm planning on running it off of a nimh pack.
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Old 10-23-07, 05:34 PM   #2
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I did a little math.

13000mcd times 90.. Gives me some crazy number. divide that by 1000 to give us candella, 1170 candella.

Pictures forthcoming :-)
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Old 10-23-07, 10:35 PM   #3
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Hey nerobro, I don't think those types of LED are going to work that well for a headlight.. I'm not sure what the angle of dispersion is, but if you convert the 13k mcd * 100 lights to lumens - even at a 15* angle that's less than 100 lumens.

I'm going the LED light route also, but your much better off with the new CREE or Seoul LEDs that'll put off well over 100 lumens each.
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Old 10-23-07, 10:37 PM   #4
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Case in point: Cree Q5 Quad hack job!
I'm looking to do a similar design as this one, but looking for a nice housing to cram it into first.
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Old 10-24-07, 07:57 AM   #5
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You can DIY a very nice bike light with a Luxeon LED and matching optics without costing you a fortune. Here is the link.
http://www.luxeonstar.com/index.php
Just select the LED of your choice considering the light output and battery requirements. Then select a Fraen elliptical lens and holder to match your LED. The elliptical beam pattern is perfect for use on a bicycle. There will be no wasted light, as you would have with a simple round "flashlight" beam pattern. My 45 lumen LED with matching Fraen elliptical lens lights up the road better than a friends 80 lumen flashlight. I chose a 1-watt Luxeon LED with a current draw of 350mA so I could use a bicycle dynamo in my lighting system. The dynamo produces 500mA. I use the extra current to slowly recharge my battery pack as I ride along. My lights never go out at stops and I never worry about my batteries going dead. If you want a lot of light you can purchase a much brighter LED with matching holder and lens combination.
I used a 1-inch PVC pipe coupler to house my LED, heat sink, holder, and lens. The PVC pipe coupler can be purchased in any hardware or building supply store for less than a dollar. I used a 1 1/2 inch EMT conduit hanger as a mounting clamp.
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Old 10-24-07, 09:44 AM   #6
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Looks nice n4zou, I'm thinking triple or quad Seoul P4 for my lights. I'm leaning towards 3 right now for battery reasons - I don't want to spend a fortune on a battery and I don't want to carry a ton of weight in batteries. The PVC pipe coupler looks good, but I was hoping to be able to find some type of metal housing so that I wouldn't need a separate heatsink.
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Old 10-24-07, 10:12 AM   #7
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I like the idea of a bar of light, especially if it could be broken into 4 parts, with 2 parts focusing ahead in the distance so that you can see the license plate of the semi that is about to run you over, and 2 parts focusing closer to the fork to let you see what dead animal you are about to run over
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Old 10-29-07, 12:49 PM   #8
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Now I am fairly sure I'll get an adequate beam pattern from my current rig. I've done a little testing on that aspect, and I'm satisfied with the beam so far. All of my testing has been done with severely underdriving the LED's. I can't wait to get them cranked up to full power.

How does having a single (or small number of) large LED(s) provide benefit over a mess of smaller ones? I'm quite impressed with the amount of light the high power LED's will throw, but if I can get away without running leds so hard they require heatsinks I may be coming out ahead in the efficancy department. That is, if I'm not disapating energy as heat, I am putting it out as light instead.

right now I'm looking at a 500ma draw off of a 9.6 volt battery pack. So.. something like 4.5 watts total (after voltage drop, connector resistance, etc..)
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Old 10-29-07, 01:12 PM   #9
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Did someone say light bar?



I'm pleased to say that I have received delivery of the first 90-LED light bar circuit boards, for anyone who wants something like this attached to their bike. The boards are designed for 11-14.4V DC, and can accept red, yellow, amber, or green LEDs. Unfortunately, white and blue LEDs require more voltage so while you could use one of these boards, you'd have to install fewer LEDs.

More pics in a separate thread when I get a bit of time...
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Old 10-29-07, 08:58 PM   #10
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Jeff,

Got a day time shot of your bike at different angles? I like the look. I'd also like to see how that tail light is in the day time from a little distance away. Sweet setup. Add a CHiP's helmet and you're good to go.
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Old 10-29-07, 09:03 PM   #11
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Originally Posted by jeff-o View Post
Did someone say light bar?


No, but you can say Kick-Ass Light Saber
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Old 10-30-07, 06:03 AM   #12
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Jeff,

Got a day time shot of your bike at different angles? I like the look. I'd also like to see how that tail light is in the day time from a little distance away. Sweet setup. Add a CHiP's helmet and you're good to go.
Yep, I'll get a few shots, day and night, once the rev. 2 prototype is finished. It's a bit shorter than the one in the pic so it doesn't get snagged as easily.
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Old 10-30-07, 07:41 AM   #13
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Originally Posted by jeff-o View Post
Did someone say light bar?



I'm pleased to say that I have received delivery of the first 90-LED light bar circuit boards, for anyone who wants something like this attached to their bike. The boards are designed for 11-14.4V DC, and can accept red, yellow, amber, or green LEDs. Unfortunately, white and blue LEDs require more voltage so while you could use one of these boards, you'd have to install fewer LEDs.

More pics in a separate thread when I get a bit of time...
If you’re a DIY person you can use a precision grinder to cut a single slot down a blank circuit board and solder 1206 surface mounted LEDs on it.


Here is the link detailing this DIY project.
http://www.pilom.com/BicycleElectronics/LEDtail.htm

Here is where you can purchase 1206 style LED's of any color.
http://www.mouser.com/search/Refine....user_Wildcards
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Old 10-30-07, 08:05 AM   #14
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Great idea, though a straight parallel configuration like that without current limiting resistors could severely limit the life of the LEDs.
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Old 11-01-07, 11:18 AM   #15
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Great idea, though a straight parallel configuration like that without current limiting resistors could severely limit the life of the LEDs.
why waste that much power when you could just use a constant current driver like a buckpuck?
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Old 11-01-07, 12:01 PM   #16
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why waste that much power when you could just use a constant current driver like a buckpuck?
The buckpuck outputs a constant 350, 700 or 1000mA depending on the model. You could string up 17, 35 or 50 LEDs in parallel (respectively) to use up all that current, but you'd still have the same problem as before, that LEDs do not necessarily have the same voltage drop. One LED might drop 2.0V, but another only 1.9V. That places a 0.1 V differential between the devices, which can cause problems. You'd need a current limiting resistor to sop up that differential. So in effect, you just wasted $18 on a buckpuck.

Also remember that it is possible to get close to the 95% efficiency of the buckpuck, if you choose the right operating voltage and number of LEDs. The less voltage you have to drop across the resistor, the more efficient you get. For instance, a circuit running from 11.1V (a standard number for a lithium pack) made of 5 LEDs, each with a voltage drop of 2V and a single resistor dropping 1.1V will be about 90% efficient. Six LEDs running from 12V will theoretically approach 100% efficiency, though you will still want a small resistor (5-10 ohms) in there just for safety's sake.
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Old 11-01-07, 02:40 PM   #17
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Great idea, though a straight parallel configuration like that without current limiting resistors could severely limit the life of the LEDs.
Just calculate the resistor required and splice it in the wire from the battery.
I use a terminal strip attached to my rear rack with the resistor mounted in it. This allows easy changes with a small screwdriver.
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Old 11-01-07, 02:56 PM   #18
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OK, again, a single resistor won't fix the problem! Each LED series chain needs a current limiting resistor. Trust me, I do this type of stuff every day at my day job!
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Old 11-05-07, 08:45 PM   #19
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OK, again, a single resistor won't fix the problem! Each LED series chain needs a current limiting resistor. Trust me, I do this type of stuff every day at my day job!
so true... But for packaging concerns I was going to go with one resistor for each pair of LED's. The LED's are not to be used in parallel.
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Old 11-06-07, 08:47 AM   #20
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OK, again, a single resistor won't fix the problem! Each LED series chain needs a current limiting resistor. Trust me, I do this type of stuff every day at my day job!
I agree with you if this was intended as a commercially produced product intended for the consumer market. As a DIY project for your own personal use and considering how cheap it can be made who cares if it blows out after several years of use. Considering the abuse it's going to get mounted on a bicycle it will most likely fail due to vibration and bumps before the LED's start burning out anyway.
Ever opened up a blinkie and looked at the circuit board? No resistors are used at all. Just a tiny chip to blink the LED's connected in parallel and two batteries. They operate for years like that as well.
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Old 11-06-07, 09:40 AM   #21
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I agree with you if this was intended as a commercially produced product intended for the consumer market. As a DIY project for your own personal use and considering how cheap it can be made who cares if it blows out after several years of use. Considering the abuse it's going to get mounted on a bicycle it will most likely fail due to vibration and bumps before the LED's start burning out anyway.
Ever opened up a blinkie and looked at the circuit board? No resistors are used at all. Just a tiny chip to blink the LED's connected in parallel and two batteries. They operate for years like that as well.
You make a good point regarding the extreme vibration and harsh conditions that the electronics will endure. There are plenty of other factors to consider as well, such as the power supply voltage, the quality of the LEDs, etc. etc. Still, resistors are even cheaper than LEDs and are still worthwhile using IMO.

Commercially made blinkies use other forms of current limiting. The chip is usually buried in epoxy potting compound and includes all the circuitry, including capacitors and resistors, needed to properly drive the LEDs.
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Old 04-07-08, 01:32 PM   #22
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I haven't forgotten this project. I've lowered my expectations for the number of LED's. I will likely end up with 50 or 70. Even 20 is enough to ride at a relaxed pace by.

My first setup was just using resistors on my 9.6v battery pack. That didn't work our very well as the change in input voltage is pretty great. My next thought was to use a Vreg to bring the input voltage down to something reasonable, and to insulate the LED's from changes in pack voltage.

From my stack of parts came one of my vregs. Bad move. They're not terribly efficient so mr 7805 got very hot and angry. Nothing burnt out, but I don't like electronics so warm I can't touch them.

I did a little research, and found that National Semiconductor makes a series of really neat simple switching power supplies. The parts count is five. How's that for a tidy solution! I got lucky, and on ebay I found an auction with 10 sets of the parts.

So... What showed up was this. A great big pile of surface mount parts. Sadly, I hadn't planned on that eventuality. Ooops. Either way, pretty parts! (as usual, click for REALLY BIG pictures)


Now.. how do you make those parts fit into a breadboard? You add wires of course! Strangely enough, It worked. And yes, it really is THAT bright.


Lights out.


So, next comes building PCBs.
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