Introduction: FlashBack - Backpack, Camelbak or Jersey Integrated LED Bike Flashers

About: Daniel Bauen breathes new life into objects that have met their untimely demise in the junk pile.
I often ride bikes that end up not having working LED flashers, either because it's a friends bike who doesn't believe in safety, mountain bike, or the batteries are dead again. Since I always bring my camelbak with me on rides, I designed some LED flashers that are integrated into the bag.

Some of the advantages that I have found to this system are:
- The lights are higher up, for better visibility then flashers attached below the seat.
- Waterproof. I've thrown the whole bag in the washing machine with the flashers attached.
- Flash timing between the 2 flashers is out of sync, creating an eye catching beat frequency strobing pattern.
- Single 2AA power source.
- Angle provides excellent side and rear visibility.
- They're always there when I need them.
- Don't need to buy separate flashers for each bike, if you have more then one.
- Could be sewn on to a bike jersey.
- You can blind the biker behind you.

Check it out at:

Step 1: Materials


- The LED flashers were purchased on sale at Electronics Goldmine for $1.50. The housing turned out to be the worst cheap plastic, and the lens barely held on. However, the LED's were some of the brightest I had seen. They are actually daytime viewable. I didn't purchase these for this project, but since the LED's were so bright, and the board was tiny, they were perfect. They have so far survived 2 years of abuse and machine washing.

- Scrap Polycarbonate - the approximate thickness I used measures 3/32 (probably sold as 1/8in) and 7/32 (probably sold as 1/4 in)

- Wires - 6 approximately 6 inch small gauge wires

- One small switch. I used a smt click switch.

- 5 minutes epoxy

- Strong thread to sew the flashers onto the bag. Preferably an industrial grade thread, like something used to sew leather.

Step 2: Dissassemble the Cheapo Bike Flasher

1. Pry off the lens, or as in my case, just turn the light over and it will fall off.
2. Unscrew the one screw holding the PCB down to the plastic housing.
3. The power and switch contacts on the back of the PCB are not soldered on, they are just touching. Take note as to where the positive, negative, and switch terminals are. You will need to solder wires to each one of these points.

Step 3: Make the New Polycarbonate LED Housing

The new housing is made of scrap polycarbonate. It doesn't take much. The thicker piece will be the back, and the thinner will be the front. One of the housings is different, because there is space for the power/mode switch, which controls both lights.

1. Cut one set of matching rectangles out of the two different polycarbonate thicknesses. Thes rectangles should be about 0.2 inches wider then the PCB on all sides. Mine measures 0.75in by 2.5in.

2. Use a dremel tool to carve out the thicker block such that the PCB with the wires behind it will comfortably fit inside.

3. Drill 5 LED diameter holes in the thinner polycarbonate. Make sure that these holes properly line up with the LEDs and that the cases line up when assembled.

4. The other housing needs to be made longer (2.75 in) for the switch cutout. I used an smt click switch.

Step 4: Create the Hookup

Time to solder the wires to the PCB.

1. Solder the power wires, positive and negative battery contacts.

2. Temporarily connect the power wires to the battery. Using a multimeter, measure which side of the power switch contact is positive. Solder a wire to the positive side of the power switch contact. This is the switch wire.

3. Drill a hole in the back case for the wires to exit through.

Note: The flasher module with the switch in the housing needs an extra wiring step to connect the switch. After soldering a wire to the positive side of the power switch contact, wire the switch across the switch contacts on the PCB. When the two switch wires are connected together between the modules, the switch will turn them both on and off simultaneously.

4. Temporarily connect everything together to make sure that it functions properly.

Step 5: Glue It Up and Drill Mounting Holes

Gluing everything together with epoxy will create a water tight seal.

Spread some epoxy around the LEDs themselves to seal the LED holes.

Partially fill the PCB cavity in the polycarbonate back piece, and put some epoxy between the front and back pieces.

Clamp the two halves together until the glue is set. Make sure the wire hole is properly sealed with epoxy.

Put epoxy around and behind the switch, but be careful not to get any in the switch.

Drill a 1/8 in diameter hole in each corner of the polycarbonate block. These holes will be used to pass thread through to sew the modules onto the bag.

Step 6: Sew It on the Bag

This requires the most basic sewing skillz, so don't worry. I sewed the lights onto my Camelbak Blowfish. It has a small front pocket that is perfect for the battery pack and wires. The wires lead directly from the light blocks into this pocket.

1. Position the light blocks near the bottom of the bag. Since you are probably not sitting straight up on a bike, have someone help you figure out at what position the lights will have the best visibility. I found it was near the bottom of the bag, such that when I lean over into my normal riding position, the blocks are almost vertical, which means that the light is being projected out horizontally.

2. Punch a small hole through the bag. I heated piece of metal (like a not so hot soldering iron) will make a nice small hole that won't rip. Pass the wires through this hole.

3. Sew the light blocks on using the holes in the 4 corners. Thread the needle through the hole and into the bag a bunch of times until you have a secure wrap. Tie off the thread on the inside, and put a drop of superglue on the knot to keep it from coming undone.

4. Inside the bag, connect both positive wires together, both negatives, and connect to a 2 AA battery pack. Connect both of the switch wires together.

5. Push the switch, and if everything is wired up right they should both turn on. Keep pushing the switch to scroll through the different flashing modes.

Enjoy, and Ride.

Let It Glow!

Second Prize in the
Let It Glow!

Park Tool Bike Month

First Prize in the
Park Tool Bike Month

The Instructables Book Contest

Participated in the
The Instructables Book Contest