With the changing seasons, and the sun rising later in the morning my commute to work is dark and unsafe when crossing busy streets. Having too many close calls with death, I decided to make a safety backpack.
The pack has 6 flashing LED's and reflective tape all over it. If anyone wants to hit me with their car now, they will have a good target. This would be a great project for cyclists, hikers, and commuters alike.
Step 1: You Will Need
-Backpack (don't use a cheap one- make a good investment)
-Reflective tape (available at most fabric stores- get the iron on variety.)
-22-24 AWG stranded hookup wire
-22-24 AWG solid hookup wire
-9v Battery clip/holster (I used a salvaged clip I got for free, but any clip that holds your batteries secure will work.)
-2 0.1 uF Capacitors (Code 104)
-2 1 M Ohm Resistors (Brown Black Green)
- 1 555 Timer Chip
- Small Slide Switch
Flush trimming pliers
Solder sucker or solder wick braid (if you mess up)
Helping hands tool
Hot glue gun
Step 2: Empty the Backpack
It may not be a bad time to clean it out too. Mine had a box of chalk that had busted open, so I vacuumed it out.
Step 3: Build the 555 Flasher
Build the circuit according to the schematic. Do not add the LED's or switch to the board. We will be adding them later on their own boards. Secure the 9v battery clip to the board with hot glue.
R1: 1 M ohm Resistor (Brown Black Green)
R2: 1 M ohm Resistor
C1: 0.1 uF Capacitor (Code 104)
C2: 0.1 uF Capacitor
Step 4: Build the LED Boards
Solder 3 LED's in series spaced evenly across the small perfboard. Make sure to check polarity - the long leg is positive. Solder them into their holes, and then twist the leads together and solder them. Leave the legs on the outside untrimmed, and mark the sides for polarity. If you forget which side is positive, bend the leads on the outside in and touch it to a 9v battery. If it lights up, you have done a good job. Mark the positive sides. Make two of these.
Step 5: Wire the LED Boards
Now we are going to wire the two serial boards in parallel. Connect the positive sides together with stranded wire, and connect the negative sides together with a longer stranded wire. Connect a stranded wire from negative to ground on the main board. Connect a stranded wire from positive to pin 3 on the 555 board. Make sure your wires are long enough to fit in the pocket where the electronics will be stored.
Step 6: Reflective Tape & Dry Fitting
Iron the tape to the backpack according to package directions. Cut a hole through the fabric and tape for each LED using the exacto knife. Dry fit the LED's in the holes to make sure they fit. Don't glue anything yet.
Step 7: Solder the Switch
Solder the switch to a small piece of perfboard. Add two stranded wires to the switches contacts. Cut a hole in the fabric of the backpack and check for fit. You may need to trim excess fibers so the switch moves freely. Solder the wires to the main board- one wire to the battery clip, and one to positive on the board.
Step 8: Testing 1...2...3...
Test the electronics to make sure everything works before gluing in place. Flip the switch a few times. Jiggle wires and make sure everything is solid. If you have a loose wire, resolder and add a drop of hot glue. You also can push the wire through the hole while the solder is hot. This pushes the insulation down toward the board and makes a little strain relief.
Step 9: Glue the Electronics in the Backpack
Glue the boards in the backpack one at a time. Don't glue the main board, because you'll want to change the battery someday. Apply a generous amount of hot glue and push the boards through the holes you cut in steps 6 & 7. Applying an excessive amount will help keep any water resistant properties the backpack may have.
Step 10: Add More Reflective Tape
Add more reflective tape to places besides the LED strip. This will keep you visible even if your batteries are dead. Follow seam lines and get creative. Make it look awesome! Don't forget to add some on the straps on the front, so you are visible on all sides.
Step 11: Use It!
Flip on the switch as you leave the door into the darkness and be visible! Remember to use common sense and follow traffic laws.