Modify your own backpack in this tutorial and give it an extraterrestrial look with smart LEDs! Use it as a bike safety gadget or just to show your love for space and your favorite constellation! The Orion constellation is one of my favorites. I'm using an Arduino Lilypad (Simple Board version) which has five PWM (pulse-with modulation) pins. These digital PWM pins can add a nice glimmer effect to the LEDs, so they look like real stars! Because the Lilypad supports up to 5 PWM pins (Adafruits Gemma V2 supports only 2 PWM pins), I recreated Orion's head (3 pins), a part of the belt (1 pin) and the right feet (1 pin). I later noticed that it kinda looks more like a mirrored Libra, which is cool though. Here is good constellation map, take a look! Which constellation will you choose for your backpack modification? So for this project you will need five white LEDs. Furthermore you need a photoresistor, a 10KΩ resistor, a small lipo battery and a lipo charger as well (you can use at least 3 AA or AAA batteries alternatively). The photoresistor controls the intensity of the light, depending on the brightness of the sorrounding. If it's getting dark the lights are more dimmed. In the sunlight the lights are brighter to be discernible (reversable in the code, so that you can save energy in bright sunlight). Besides the photoresistor produces a cool shining effect of the LEDs, like real stars! If you prefer, you can use ultra bright LEDs (by Adafruit for example) to make your backpack more noticeable especially in bright light. To power the Lilypad I'm using a lipo battery pack with 3.7V and 400mAh. When activated, the backpack lasts about 8 hours (which is pretty good in my opinion). To upload the code to the Lilypad, you need an FTDI module/adapter and wires.
Summary of material needed:
• 1 Extraterrestrial Backpack (I have a Spiral Galaxy Saturn Backpack)
• 1 Arduino Lilypad (Simple Board)
• 5 White Lilypad LEDs
• 1 Photoresitor
• 1 10KΩ resistor
• 1 FTDI module/adapter and wires
• 1 Lipo Battery (3.7V with at least 400mAh) and a suitable charger OR 3 AAA or AA batteries in a battery holder
• Conductive thread and a (large-eyed) needle
• Optional: Geeky and nerdy stuff for more decoration
For this tutorial you need a few sewing and programming skills! If this is your first time with a Lilypad and sewing with conductive thread, I can recommend this page for beginners!
Step 1: Plan Your Modification
When an idea comes into my mind I'm only thinking about the basics of my project:
What do I need and where do I start?
To be honest - I'am not a great planner sometimes. I just like to start and see what happens and solve problems while crafting. But it's important for this project to think of the Lilypad's and LED's location. Also think of a plan for the stiching lines of your conductive thread. For example sew only one line of thread leading to ground (GND) as shown in the picture. It might help if you draw a little sketch before starting. Place the Lilypad in an upper area of the inner side of your backpack. It is way easier to switch it on/off and to avoid damage by stuff your carrying, as if it would placed in a lower area.
Step 2: Sewing
Start sewing by fixing the Lilypad with a few stiches. At this point sew only through the first inner layer of your backpack so nobody can see the stitches on the outside. I made a little drawing to show you what I mean (backpacks normally have two separated layers). Then I placed the first LED on the outside of my backpack. When fixing this LED, I sewed through both layers (as shown in the picture). We need to use PWM (Pulse-width modulation) pins to generate dimming effects. PMW pins are 5,6,9,10 and 11. Now sew a line from the Lilypad to your first LED. Stay on the inner layer until you finally reach the LED. Repeat these steps with all of your LEDs. Don't merge the positive (+) line of your LED with another LED. Afterwards you have to connect all of your LEDs to GND (-). You can merge your negatives lines here!
Before you're finished it's time to integrate a photoresistor to make this backpack super smart! Now find a good spot on the outer layer and sew the photoresistor in place. I placed mine on the backpack's top so it's affected by direct sunlight. Connect the positive pole with pin 19 and the negative with GND (-).
Step 3: Programming
Simply download the code for this project from my Github repository. Modify it, if you like!
Connect the FTDI device to your Lilypad. Now configure your Arduino IDE: Select Tools in the menu and set the Arduino Lilypad as your board. Select the highest port available as well. Finally upload the code. You can see the LEDs start to glow now. If not, check the connection between the FTDI and the Lilypad. Has the code uploaded correctly? Furthermore check your stitching lines. Is there a bypass? Afterwards remove the FTDI and plug your fully loaded lipo battery in. Turn your Lilypad on and enjoy your little space illusion!
Step 4: Congratulations!
Congratulations to your very own glowing and super stylish space backpack modification! Decorate your backpack with some neerdy and geeky stuff to make it even more special! See you out there... and get yourself some ice cream for the excellent work of yours! <3
Please note that you need to remove the battery if it rains or you will damage the circuit! You can use some clear nail polish to give your LEDs a little isolation. Other parts like the LEDs and your Lilypad don't get damaged if they get wet (battery has to be removed!). Wait until everything is dry, before pluging the battery back in. You can still handwash your backpack carefully, if you like.