Ever wanted to be seen at night while biking? Ever wanted to know what's below your feet before you step on--or in--it? Or just want some side visibility so you don't get run over by cars/trucks/other bicycles at crossings?
This is a simple solution to get better lighting on your bicycle, in order to be better seen. A visible biker is a safer biker. It has additional benefits, such as giving you a good view of your chain line (to tell what chainring/sprocket you're in), or allowing you to avoid stepping into a pothole or other unsavory mess on the path.
It's not exactly cheap, but it's not terribly expensive either. And, if you're like me and own several bikes that you ride at night, the cost per bike goes down with each additional bike; you only need one charger and one battery to share across them all. Lastly, they are as waterproof as you like, so during the rainy/snowy nights when lighting is most critical, people can still see you.
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Step 1: Procure Tools, Lights, Battery, Etc.
You will need several tools for this project. They are:
1. Wire stripper
2. Wire cutter
3. Soldering iron
4. A lighter or some matches (for shrink tubing)
5. Steel screwdriver (for mixing epoxy)
6. Hobby knife
You will also need the following supplies:
2. Epoxy (30 minute is probably best, but 5 minute will work too)
3. Shrink tubing (small is needed, but a larger size is good in addition)
4. Waterproof yellow LED strip(s)
5. 12v (or lower) rechargable battery pack
6. Charger for battery pack
7. Tamiya or similar connectors
8. SPST switch for easy on/off (optional)
9. Seat pack for your bike if you don't already have one.
10. Thin (high gauge) speaker wire or similar paired wire.
11. Zip ties to attach light strip(s) to the frame.
12. Electricians tape ("E" tape)
I bought my LED strips from LED Wholesalers. The exact product I bought can be found here. I would recommend you buy yellow (AKA amber) because this is the only color legal in all directions. The battery, charger, and Tamiya connectors were all purchased from All-Battery. I can no longer find the same battery pack that I purchased, but this one should work just fine. They also recommend the charger for that particular pack on their site, and they sell Tamiya connectors, which is what the charger I used came with.
You will need two Tamiya connectors, one male and one female. Alternatively, you can buy three connectors (2 male/1 female or 2 female/1 male) of something more waterproof than the Tamiya connectors, but you will need to do some additional soldering of the connectors to the charger. Everything else I had lying around, but can be purchased online from components stores such as Mouser, or possibly at a local Radio Shack or hobby store.
Step 2: Solder, and Charge the Battery
Take the battery with its bare leads and your Tamiya or similar connector that is the opposite sex of the charger's connector. Strip the ends of both if there is not enough to solder to. Place shrink tubing over the black lead from the battery, and solder it to the black lead on the Tamiya connector. Move the shrink tubing over the solder joint, and heat it with a lighter to shrink it tightly around the joint. Be careful to not light the shrink tubing on fire.
Now, solder the red lead on the battery pack to one of the leads on the switch. Solder the red lead of the connector to the other lead of the switch. You can't use shrink tubing here, but there are other methods to waterproof which is covered in a later step. If you don't want to use a switch, just solder the two leads together after placing shrink tubing over one of them. Once it's all together it should look similar to what you see in the photo.
Then start charging your battery while you continue to work on the next steps. Make sure you test your switch if you chose to use one.
Step 3: Prepare LED Strip
The strip itself is fairly long (0.5 meters/~20 inches), so I chose to cut it in half. Note that you can only cut every 3 LEDs, at the areas marked by a dashed white line and a small scissors. I suggest cutting them with a wire cutter that can cut the whole strip in one snip.
Also, realize that it has only two leads, one on each end, so cutting it into two parts is not a big deal. If you want to cut it into more parts than it has leads (3 or more), you will need to solder additional leads directly onto the PCB. While it already has some easily visible solder patches for this, it's fairly difficult to do without potentially damaging the waterproof housing around the PCB, so I don't recommend it. It also makes final wiring and waterproofing more difficult.
After cutting it at one of the designated cutting lines (if you desire), cut off the waterproof plugs on the end of the wires. Separate the wires by cutting between them with a hobby knife. Then, strip them so you can solder directly to the leads. The picture shows exactly where you should be at this point. Make note of which lead is positive and which is negative by looking at the PCB though the waterproof covering.
Step 4: Waterproofing, Part 1
Now, mix up a small batch of epoxy in a disposable plastic container with a steel screwdriver. We will be using epoxy to waterproof because it is permanent and non-conducting. You will be soldering three things with this batch of epoxy. They are:
1) The cut ends of the LED strip, if you cut it.
2) The wires going into the back of the Tamiya connectors, if you used them. If you used a more waterproof connector, this will not be necessary.
3) The back of the switch, if you are using one. It's also probably a good idea to epoxy the black wire on the back of the switch, to keep the wires together.
The pictures speak more than words here. Just make sure you don't dawdle if you are using 5-minute epoxy. That stuff hardens quickly!
Apologies for not taking pics immediately after this step, but I took some after the whole project was done to illustrate the application points.
Step 5: Attach the Lights to the Bike
Now, zip tie the lights to your bike where you want them. I chose the left chain stay (pointed down toward the ground) and the bottom of the down tube, to illuminate the ground below me.
Also good is to put them 45 degrees between down and sideways, where they can be seen from your side, but also won't be directly visible from your eyes (which can hurt your night vision). Other good places to place the lights are on the seat stays and along the side of the fork.
You'll want to use at least three zip ties to attach them securely. You can use far more, if you want, just make sure you put them between the LEDs and not covering them. If you bend them around curves, I recommend a zip tie every other gap between LEDs.
Step 6: Solder Lights & Connector; and Waterproofing, Part 2
Now comes the fun part. With the lights on the bike, measure out how much speaker wire you need to connect the lights, from your seat bag to the leads on the further (from your bag) light strip. Cut the wire, and split the two wires near the ends with a hobby knife. Then strip the ends, place a piece of small shrink tubing over each wire, and then one larger piece over both wires, and solder the wire leads to the first two leads on the first strip. Make note of which color (or sometimes marked with a white stripe) of speaker wire is soldered to the positive lead, then shrink the small shrink tube over each solder joint. Finally, slip the large piece of shrink tube over both of the smaller pieces, and shrink it down to hold them both together.
Once the first strip is soldered and the tubing has been shrunk, run it along the frame to double check the length is enough to reach your bag. Then, if you can reach the leads of the second light strip to the wire running along the frame, trim off some of the insulation around the speaker wire using your hobby knife and solder the leads of the second strip on, making sure the positive is soldered to the positive and negative to negative. They're diodes, remember, and will not work if the leads are mismatched.
If you can't reach the wire going to the further strip with the leads from the second, simply solder on longer leads with some additional speaker wire. Use the same shrink tube method I described earlier to keep everything waterproof and uncluttered.
Remember, be patient in this step. It's not easy to solder components while they're attached to the bike, but it's necessary to get the right lengths of wire. You don't want any extra wire, because extra wire can flap around and get caught in your cranks/pedals/spokes.
Mix up another, even smaller batch of epoxy. You will want to cover any place you have spliced LED leads into your speaker wire with epoxy, to prevent shorting and waterproof the system. If you have only two "half-strips" of lights as I do, you will only need to do this in one place. Take a look at the image of the left side of my front derailleur to get a detailed image of where my splice was, and how it was covered in epoxy.
Now, double check the routing of your speaker wire. I managed to route it under the bolt securing my front derailleur to the frame, which keeps it tucked well away from the wheel and cranks. I also stuck it to the seat post by putting it under the clamp that attaches my bag to the seat post. Be inventive, and make sure there isn't any slack to get caught on anything.
Finally, tape down the speaker wire to the frame to ensure it stays put. Use as much tape as necessary. Once you get up by the seat bag, solder on your Tamiya or similar connector to the ends of the speaker wire, keeping red to positive and black to negative. Don't forget the three (or two, if you don't have large shrink tubing) pieces of shrink tubing to keep everything from shorting.
Step 7: Secure Connector, Add Battery, and Turn On
Zip tie the connector to your seat rails, to keep it from flopping around when you don't have the battery connected. Place the battery in your rear pack, and plug it in to the lights. The connection here is the most prone to water leaking in and shorting the circuit if you are using the Tamiya connectors.
There are two ways to solve this--the crude way is just to wrap the whole thing in plastic, but the slick way is to put a very thin ring of rubber around the female connector, that is pinched when the male connector is plugged into it. This will seal the Tamiya connectors completely, but unfortunately I haven't taken any pics since doing this.
Now that everything is connected, flip the switch and it should turn on. If you didn't use a switch, it should have turned on as soon as you plugged in the battery. If you don't see any light, you either reversed the polarity (likely), a short (also likely), bad solder joints (somewhat less likely), or have bad LED strips (unlikely). If one strip lights and not the other, you probably reversed the polarity on that strip and not the other, or have a bad solder joint or a bad strip (or partial strip).
Pack everything in and secure any loose wires as shown in the photos, and finally...