I know what you are all thinking, yet another of the dozens of LED bike lights, well needless to say I am taking a slightly different spin on the idea. After reading Mackstann's instructable on his LED backpack bike light
I knew I had to build one that would fit my needs. The challenge I faced was that I don't use a backpack, I carry a Timbuk2 messenger bag
which uses only one strap. The problem is that whenever I put on the bag and go riding I sinch up the main strap, so the light needed to be able to slide or strap onto the strap. I also wanted to contain all the batteries and electronics on the strap, so I would avoid having to run wires all over the place.
I only want front lights because I have a Lithium Glo-toob
on the back of my messenger bag which works fine. I will use two of the White 100 Lumen Endor Stars
and an 8 "AA" battery pack.
Output - 360 Lumens
Power - 6.7 Watts
Runtime - 3+ hours
Batteries - 8x 1.2v Ni-Mh
Cost - $120
Step 1: Parts List
2x Endor star lenses
1x Tube of silver thermal epoxy
1x 700mA Powerpuck driver
2x Endor star 100 lumens (180 @ 700mA)From LED Supply
1x JB Weld (Mackstann thank you for introducing this to me, it works so much better than silicone)Any of these Dealers
1x 8 "AA" battery holder
1x 9v battery snap
1x Miniature Toggle switch
Radioshack (so over priced)
1x Camera/ iPod / Gadget pouch
It is this little $8 pouch that brought my entire project together (wow that's sad), because this was the enclosure that needed to attach to my bag strap. It was after some fiddling around with the 8 "AA" battery pack that I realized it fit perfectly in my small camera bag, well circuit city has dozens of these to choice from so I took a trip down there and found exactly what I needed. It has a firm clasp that won't slide around even when riding, and the LEDs can pop right out of the top.
Parts I already had lying around:
-8 AA Ni-Mh batteries and charger.
If you are looking for Aluminum or anything else for that matter go to Mc-MasterCarr
You will also need basic soldering supplies, and shrink wrap helps
Step 2: The Electronics
The electronics for this project were rather simple to figure out, as you can see by the diagram. We begin with 8 1.2v Ni-Mh batteries which give us 9.6v. All of the current regulators I have used have what the PDF refers to as a "2v margin" which basically means that the regulator eats 2v, so you can subtract that from what your LEDs receive. So, our 9.6v drops down to 7.6v due to the regulator, and because our LEDs are in series we divide that value by 2. This gives us about 3.8v @ 700mA per LED, which is close enough to the suggested value of 3.4v @ 700mA. I hope this cleared up any confusion anybody had about the electronics in the system.
Step 3: Mounting Heatsink
Ok there are obviously many ways to do this, all you have to have is a place to put your electronics, and be able to heatsink. For mine I used three parts: the battery holder, small PC heatsink, and an Aluminum plate I had lying around. I used JB Weld to bond everything together, don't forget to sand and clean all of your parts, No. 60 sandpaper works well. I began by bonding the aluminum plate to the heatsink and then with the battery holder in the vice I bonded every thing together.
If it is your first time using JB weld I recommend you get a clean place to work in and wear gloves or keep some paint thinner near by, because this stuff can make a mess.
Sorry I didn't get individual shots of the components, I got so busy making a mess with the JB weld I forgot to grab the camera.
Step 4: Mounting Switch
This will depend on what type of of heatsink you have, but mine had a big gap in the fins that provided ample room to bond the switch with JB weld. I recommend that you lay everything out before soldering and bonding, this will assure that you have room for all your parts and that your wire lengths are correct. Remember the adhesive is the LAST thing you open up. I soldered the negative wire from the regulator to one of the terminals of the switch and another piece of black wire to the other terminal, flux will make this easier, it will not look pretty, but it is getting covered up with heatshrink and jb weld so it really doesn't matter.
I tried filling the area that I was going to put the switch with JB weld, and then pressing the switch into it, I then applied a second coat in order to completely encase the switch.
Step 5: Mounting the Regulator
This step got a little messy, because the JB weld is difficult to get into the tight spaces. What I tried to do was bend the mounting bracket back on both sides so that it would slip into the fins of the heatsink. I applied JB weld to the bracket and tried to slop it in the fins, you can judge the results for yourself and learn from my mistakes.
Step 6: Bonding and Soldering the LEDs and Lenses
Now we are finally going to install the LEDs, remember don't bond the LEDs on until you are sure they are functioning, that way if you burn one up or instaflash it you can still replace it. When you are soldering the output wires from the regulator to the LEDs make sure you use the terminals that are closest to the LEDs, the others will not work! This is never mentioned on the PDF, and it had me scratching my head for a little while trying to figure out why it wouldn't turn on. If any of this confuses you just refer to the picture.
This is were we will use the silver adhesive to bond the LEDs to the heatsink, you don't have to use it, but I would at least recommend using some kind of thermal compound, it will help keep the LEDs nice and cool. The best part of the thermal adhesive is that it sets-up in 5min, the main reason that this project has taken so long is that I have been waiting for adhesive to dry.
I am aware that my soldering on the LEDs is sub-par, but these solder pads are very small, and I am going to encase the entire thing in JB weld so hopefully it won't matter.
Before the silver adhesive has dried it is time to apply the lenses. To do this just press the lenses unto the LEDs letting the standoffs sink into the silver adhesive, and then liberally apply the JB weld to bond them on. I expected this to be a lot more messy than it was, and I thought they turned out ok.
Step 7: Review
In retrospect I think I should have gone with a standard handle mounted LED light, because although the Rebel LEDs put out a stunning amount of light it is flooded so much I can only see about 10-15ft in front of me when riding, I generally prefer a spot to help me avoid potholes. Due to the nature of the tri-LED configuration I can understand why the only optic they offer for it has a 25 degree spread. Don't get me wrong, this light has many pros, you are very visible when riding, you get the added benefit of having the light come with you when you get off the bike, and it is streamlined with no wires running all over my bike, which I personally don't like. Overall I plan to use the light on a regular biases, until I build a superior revision.
Well I hope you guys and gals liked my first instructable, and go ahead with the criticism I can take it, that is what makes my projects better.