I was re-published on TreeHugger!!! http://www.treehugger.com/slideshows/gadgets/how-make-led-turn-signals-your-bike/

Turns out the guys at CleanTechnica and WonderHowTo blogged about this without telling me first. Not sure if I should be upset or happy, haha. Check it out:
http://cleantechnica.com/2012/10/17/led-turn-signals-for-your-bike-by-a-9th-grader/
http://cycling-lessons.wonderhowto.com/how-to/add-led-turn-signals-your-bike-for-safe-road-cycling-0138678/

I made a schematic using Upverter! This should help a lot of people.

Update 8-5-12: Thanks so much guys for the homepage feature AND the newsletter feature! I've always wanted one of my instructables in the newsletter!

Hand bike signals are boring, and who doesn't love electronics and LEDs? I don't do much road biking where I actually need turn signals, but they look cool and are fun to make. Also, they go great with an Altoids Bike Headlight on the Cheap! (That's another one of my 'ibles.)

~~~If you like this, please please please vote for it in the Bicycle, LED, and Hurricane Lasers Contests!~~~

**Video of the turn signals in action coming soon!**

Step 1: Ingredients

1- Project Box 3x2x1. UPDATE: scratch this. Use a bigger one! The pins from the switch didn't fit inside so I had to mount it the wrong way, and the battery didn't even fit! I would suggest using one at least a 1/2 inch bigger on all sides.
3- Velcro Straps or Hose Clamps - you could use zip ties, but then you would have to cut them every time you needed to remove the turn signal system for transportation.
1- Project Box 5x2.5x2
2- 10 ohm resistors
1- 9V battery snap
1- Center Off 3-way toggle switch
10- 5mm Yellow Flashing LEDs. Get some that require 1.8V so that you can use a 9V battery.
10- 5mm LED holders
2- old bike reflector mounts (one rear mount and one front mount)
1- 9V battery
Hot glue or super glue
Screws
Drill with assorted bits
Solder & Soldering iron
Screwdriver

Step 2: Reflector Mounts

First, you need to disassemble the reflectors to get the mounts. All reflectors are different, so you're on your own for this step. For mine, I just needed to bend back a little piece and it popped right off. I also needed to sort of combine two mounts to make a rear mount that would work. Now mount one on the front and one on the back like shown in the pics.

Step 3: Switch-box

Now we need to make a switch box. This will house the toggle switch and battery. First, we need to decide how we want to mount it on the bike. I will mount it beside the left handlebar and use a screw to attach it to the reflector mount. Now drill a hole for the toggle switch to fit in wherever you want. The box is really easy to drill through, so be super careful! Mount the switch to make sure it fits, then remove it so you can wire it up. Wire the middle pin of the switch directly to the positive lead of the battery snap. On both of the other pins, solder a 10 ohm resistor. Then solder a wire to each of those resistors that can reach the rear reflector mount with about 6" of extra wire for safety. Use heat shrink if necesary. Now solder two wires of that same length to the ground wire of the battery snap. Drill a small hole in the bottom of the box and feed the wires through it. Re-mount the toggle switch, secure the 9V battery in the box, and close it. My battery didn't fit in the box because of where I placed the toggle switch, so I had to use a dremel and cut a slot for it to stick out through. I covered the protruding end with electrical tape. Don't mount it on the reflector mount yet.

Step 4: Wiring & Mounting the LEDs

Using a nail or other sharp object, make 10 dots on the larger project box in the shape of left and right arrows (5 LEDs per arrow). Be sue they are spaced apart enough so that the LED holders won't touch. Drill the holes and place LED holders and LEDs in. Turn the LEDs so that all the positive leads are facing the same way and the negative leads are facing the same way. If needed, use hot glue or super glue to secure the LEDs in. Bend all the + leads of the LEDs. Connect all the positive leads of the LEDs of one arrow with wire. Leave a little peice of wire sticking out of the bottom LED. Repeat for the next arrow. Now use this same method to connect all the negative leads of one arrow, and then the other. Solder them to ensure a good connection. Now you need to drill a small hole in the side of the box opposite your LEDs and feed the wires coming from the switch box into the hole. On the bottom LED of each arrow, attach one of the wires from the switch to the positive lead. Also solder a wire from the ground wire of the battery lead to the negative lead of the same LED. Once everything is connected, test it out to make sure it works and then close the project box. If it doesnt work, make sure all the connections are solid and that none of the leads are touching if they dont need to touch. Mount it on the reflector mount using any method you want (glue, screws, etc.). If you're using a drill, be sure you don't drill into any components in the box.

Step 5: Mounting It on the Bike

Mount the switch box so that when you flip the toggle switch up, it turns on the right arrow and when you flip it down, it turns on the left arrow. This is how the turn signals work on a car. If you don't want to do that, you could mount it so that flipping it left turns on the left arrow and flipping it right turns on the right arrow.

Now mount the LED box on the back.

Step 6: Securing Wires

Use zip ties or velcro straps to secure the wires along the frame of the bike. Be sure to leave enough slack at the front so that the wires don't hinder your ability to turn. If you still have some slack, push it into the larger project box (there's plenty of room in there).

Step 7: Go Riding!

Now go riding on the road and show everyone your new and awesome bike turn signals. You may even get some requests from some friends to install some on their bike! Be sure to charge them a good amount, though!

If you have any questions, feel free to ask! I'll be happy to answer any questions.

Thanks for looking!

Step 8: Hurricane Laser Cutter

Now, since this is in the Hurrican Laser Cutter Contest, I need to tell you what I would do with one of their amazingly cool and awesome and robotic laser cutters.

First of all, I like to do papercraft. Now I am using a hobby knife to cut all the pieces out, which makes it look terrible and is very time-consuming.

I also like to do some woodworking, and this would allow me to make precise cuts on my projects.

Third, my dad owns a business called Memory Links (www.memorylinks.com) and has to send his pieces off somewhere to get them laser engraved. My dad would most likely be very excited if I took the laser cutter to his office so he could manufacture his own Memory Links.

Fourth, I make paracord bracelets and have been wanted to put dog tags on them. I have the dog tags, just no way to put custom messages on them.

Wow, I have a lot of uses for a laser cutter! Please vote for me!

Wait! One last thing. I will also post an instructable on everything I do with the laser cutter if I win it!

Thanks!