Introduction: Convertible Solar Safety Bag With E-textile Loomia Tech

About: Tech Couture Design Studio and Authors of Make It, Wear It: Wearable Electronics for Makers, Crafters, and Cosplayers.

This project showcases the flexible, low-profile e-textile components by Loomia Tech. Go from hikes, to the beach, to biking at night with this convertible backpack/tote bag that charges your phone with Solar energy and lights up for safety with addressable LEDs. The Loomia Electronic Layers (LEL) in the strap of the bag makes a durable and functional control for the lights.

Loomia e-textile components

This project combines electronics, programming microcontrollers, sewing, and 3D printing.

The code, pattern pieces, and 3D printed electronics case are all available as a downloads with this Instructable.

You could use the components to alter a store-bought bag if you only want to make a backpack or a tote bag. If you do not have a 3D printer you can print the case for the electronics with a printing service like Shapeways or substitute a purchased box of a similar size.




All purpose 11" or 12" plastic zipper

80/12 sewing machine needles

All purpose polyester thread to match your fabric and to match your cork fabric

Clips to hold cork fabric

4 x 1.5" D rings

1 yard 1.5" straping

Sewing pins

Other supplies:

Crazy glue gel

Hot glue sticks

Double sided tape


Computer for programming

Sewing Machine

Serger (optional)

Soldering iron for electronics

Wire cutters and stripers


Hobby/Craft/Exacto knife

Glue gun

Leather hole punch

Awl for sewing or leatherwork


Rotary cutter and cutting mat (optional)



Step 1: Download Files for Patterns, Code, and 3D Printed Electronics Box

Bag Pattern

The bag pattern is available as a download. If you have an 8.5 X 11" paper printer you will need to tile the pattern and tape it together. Here is a link to instructions on tiling and printing

There is a 1 inch square at the bottom left side of the pattern. If that square measures 1" all around your pattern is printing correctly.

You can add these electronics into an existing backpack or tote bag, but you won't be able to convert the bag from backpack to tote.

Code for Lights

Download the solarBag.ino Arduino sketch.

Arduino files need to be in a folder with the same name as the file. When you download the file here and try to open it you will get a message that says "The file "loomiaBag.ino" needs to be inside a sketch folder named "loomiaBag". Create this folder, move the file, and continue?". Click Ok and create the folder.

3D Printed Box

A 3D printed box protects all your electronics for this project. You can print this on your own filament print, use a printing service like Shapeways, or substitute a purchased box of similar size.

Download the solarBoostBoxV2 v11.stl for the box.

Step 2: Cut Out the Bag

1. Cut out your paper pattern and place flat over your fabric and interfacing. Each pattern piece will tell you how many to cut out of your fabric, and how many to cut out of your interfacing. The cork fabric pieces do not need interfacing.

2. Using scissors or a rotary cutter cut out all the pieces from fabric, interfacing and cork fabric as labelled on the pattern pieces. In addition to the pattern pieces you will also need to cut some pieces of the cork fabric using a ruler.

Other Cork fabric pieces: 2 of 27" x 2" strips for the bottoms of the straps; 1 of 5" x 5.5" for the solar panel mount; 2 of 1.5" x 13" for the LED strip covers.

3. Fuse the interfacing to the fabric with an iron. Place the shiny side of the interfacing on the wrong side of the fabric. Heat the iron to a wool setting and turn on the steam. If your iron doesn't have steam you can use a damp pressing cloth or dish towel. On an ironing board or ironing mat, press down on the interfacing for 10-15 seconds to attach. Pick up the iron and place it down on the next part of your fabric, don't glide across the fabric.

Optional: As a design choice you can round the corners of the solar panel mount (see photo), and the end of the strap.

Step 3: Wire Your LED Strips

We've found it useful to connect components with a JST connectors so that you can disconnect them easily to assemble the bag or swap out parts if they get damaged and you need to replace them.

1. Learn how to Solder using the Adafruit Guide to Excellent Soldering

2. Cut two 10" long LED strips. The Adafruit guide to Neopixels is a good resource for learning how to cut, solder and use addressable leds/neopixels (Neopixels is an Adafruit brand name for addressable LEDs).

3. If your LED already came with a JST-SM connector, you can solder the same connector to the fresh cut strip

4. Pick either the plug or socket end of your JST connector. It should have 3 wires. Strip a bit of the end for soldering. One is usually red (power), the other side is often black or white (ground), and the center wire is data. Solder the ground wire to the GND pad on your LED strip, solder the data wire to the center bad on your LED strip, and solder the power wire to the PWR or V pad of the LED strip.

4. Repeat with another of the same JST connector on the second LED strip.

Optional: Add some hot glue where the wires attach to the LED strip for strain relief.

5. Make a Y connector for your strips. Since we want both LED strips to do the same thing at the same time we can ultimately wire them together into out Arduino. We are going to do this with a Y connector.

Optional: Tin the ends of all your wires before you get started.

6. Use 2 of the matching JST connectors to your LED strips. If you used plugs on your strips, you would use 2 sockets; if you used two sockets on your LED strips, you would use 2 plugs.

7. Match up the wires for your two connectors. Power goes with power; ground goes with ground; data goes with data. Strip some of the coating and twist the wires together. Slip some heat shrink tubing over and past the ends of your two wires that are twisted together.

8. Take a third JST connect and twist the ends of that connect to the wire you already have, matching power, ground and data.

9. Solder each of your 3 wire bundles together.

10. Move the heat shrink over the wire you soldered together and use a heat gun to fix it in place.

Step 4: Add the Solar Panel and LEDs to the Bag Front

1. Use the leather punch to cut out holes for the electronic components, as follows.

2. Place the solar panel on the cork solar panel mount. Using a pen, mark where each of the 4 screws on the back of the solar panel touch the cork. Mark where the wire on the solar panel touches the cork. These are shown in red on the photo.

3. Using a leather punch, cut holes at each of your marks. Carefully use scissors to make the center hole for the wire a little bit bigger (about 1/2") so the barrel connector can fit through. Unscrew the plastic ends off the solar panel screws and make sure that the screws and wire fit through the cork fabric.

4. Measure up 1.5" from the bottom of each of the cork LED cover strips. This is where your first LED will go. mark the center of the cork strip with a pen matching where each of the LEDs will need to be. Each of your LED strips is 10 inches long, the amount of LEDs you have will depend on how many LEDs per meter are on your strip. For this example we used 60 LEDs/meter.

5. Using a leather punch, cut a hole for each LED.

6. Glue the cork strip over your LED strip using either hot glue or crazy glue gel.

7. Repeat for second LED strip.

8. Put the solar panel mount on the right side of the fabric on the front of the bag. Measure 3 inches from the bottom of the front piece and 3.75 inches from the side. This is where the left bottom corner of the solar panel mount will go. It should be centered on the front of the bag. Use some double sided tape to hold the cork piece on to the front of the bag.

8. Using a long stitch length on your sewing machine, sew the cork fabric to the front piece approximately 1/16" to 1/8" in from the edge. Remember to do a lockstitch at the front and end of your stitching.

10. Measure 1.5" inch in from each side of the front, this is where the LED strips will go. Measure between 1" and 1.5" up from the bottom of the front along the LED strip placement. Using the awl and scissors, cut a small hole just big enough for the JST connector on the LED strip to fit through the front fabric. Pull the JST wire through so the LED strip lays flat along the front.

11. Use double sided tape to hold the LED strips in place. Using a long stitch length sew the cork covered LED strips 1/16" to 1/8" from the edges of the cork fabric (shown as a red line in the photos). There will be extra cork fabric along the top curved edge of the bag front. Trim off with scissors.

12. Once the LED strip is on the bag, let's make sure the solar panel fits. Use an awl to make a hole through each of the holes on your cork fabric and the bag fabric. You will need the scissors to make the hole large enough for the connector on the solar panel. After making certain everything fits, remove the solar panel and set aside so it doesn't get damaged in the construction of the bag.

Step 5: Sew the Bag

1. Topstitch the strap on the front of the bag - The cork fabric strap has a front piece that is 4" on one short edge, and two 2" pieces on the other short edge. Measure 9 inches up from the bottom edge of the front piece of the bag and center the short 4" side cork fabric strap pattern piece on the bag front with the wrong side of the cork fabric on the right side of the front fabric. Topstitch in a U shape along 2 inches on each side of the cork piece and the 4 inches along the lower edge (see diagram). Topstitch the very center of strap from the center of the lower edge to where the piece splits into 2 straps. This will help secure the straps onto the bag. Once these are sewn, roll up rest of the straps so they stay out of the way for the next steps.

2. Inside pockets on front of bag.

2a. Fold over the top edge of the Large Electronics Pocket 1/4" inch twice and iron. Sew down top with a straight stitch.

2b. Fold over the top of the Small Electronics pocket 1/4" inch twice and iron. Sew down the top with a straight stitch. Fold in the two sides 1/4" once and iron. Place the small electronics pocket centered on the large electronic pocket with the bottom edges even. Sew along each long side of the small electronic pocket; shown in red in the photo.

2c. Line up the Large Electronics Pocket wrong sides together with the wrong side of the bag front, matching bottom edge and side edges. Baste with a long sewing stitch along the sides and bottom of the pocket and front to attach together as one piece.

3. Strapping on back piece of bag

3a. Cut the 36" of strapping into 2 pieces of 18". Finish one edge of each strap by folding it over 1/2" and then 1/2" again. Sew horizontally across the folded section to finish it.

3b. Fold the other end of the strap over 1". On the right side of the fabric of the back piece of the bag, measure 1" up from the bottom and 1" in from the side. Place the folded section of the strap facing the right side of the fabric. Sew the strap securely to the back piece by sewing horizontally, vertically, and in an X shape to attach the folded part of the strap to the back piece of the bag (see diagram). Repeat on the other side of the back piece of the bag so there is a left and right strap. Roll up the straps and clip or pin to keep them out of the way for the next steps.

4. Matching right sides together of the two side pieces, sew the bottom edge of the pieces together with 1/2" seam allowance remembering to do a lockstitch at the beginning an end of each seam. Iron open after sewing.
Optional: Finishing seams is optional. You can use a serger as in one of the photos, or a zigzag stitch.

5. Sewing front to side

5a. Right sides together, start sewing one long side of the side pieces to the right side of the front piece with a 1/2" seam allowance. Sew along both pieces to the corner of the front piece.

5b. Leave the needle in the fabric, lift the presser foot and pivot the front piece to line up the side seam and bottom of front pieces. Lower presser foot and continue sewing along the seam of the side piece. You may need to make a small cut at the corner to turn it smoothly. Sew along the seam to the next corner.

5c. Leaving the needle in the fabric, lift presser foot and pivot to last side of front piece. Replace presser foot and keep sewing the last side.

5d. Reinforce the corners, as shown in the photo, by sewing a small seam at the corners.

6. Repeat step 4 with the back piece until front, sides and back piece are attached.

7. Turn in seam allowance on long edge of top pieces; press.

8. Center zipper on long pressed edge of top pieces. Pin in place. Sew 1/8" from zipper teeth. Using a zipper foot is recommended. Sew both sides of zipper in between top pieces.

9. Open Zipper. Fold the top piece in half, longways along the zipper. Stitch top sections together at the short sides.

10. Pin top piece to upper edge of the bag, matching the short seams of the top piece to the center of the front piece and the center of the back piece. Carefully pin in place. Stitch along edge. Turn right sides out.

11. Form the tabs for the loops.

11a. Pull the top piece of the bag with the zipper horizontally so that it is a rectangle. Fold the edges of the right side down to form a triangle. Pin in place. Sew along the bottom of the triangle 1/4" away from the existing seam. Line up the cork fabric loop piece with the sewn triangle. You will see that there is fabric that will extend into the center of the loop. Cut off this extra fabric near the seam you just sewed to make the tab.

11b. Make a sandwich of the wrong sides of the cork fabric loops with the fabric tab in between (see photo). Clip to hold it in place. Topstitch the Cork loops together. Sew with a long straight stitch approximately 1/8" to 1/16" from the edge. Sew the inside of the loop also. Trim any uneven edges.

11c. Repeat for the other side of the top at the other end of the zipper.

Step 6: Assemble the Loomia E-textile Components

We'll be using the LEL Single Backlit Button to control the LEDs on the back of the bag. The button will placed on the shoulder strap close to the hands, far from the electronics that are also in the back of the bag. We will use two LEL .15" 4-Wire Buses to connect the button to the microcontroller. The Loomia buses are ideal for the shoulder strap since they are flexible and thin. The prototyping buses are 12 inches long, so we'll be using two buses for the shoulder strap.

The Loomia prototyping components have a combination of though the hole pads and bigger soldering pads similar to those found on the addressable LED strips. We'll be cutting off the through the hole connectors and connecting components by soldering abutting pads. We'll leave the last though the hole connector in place to solder wires that will eventually be soldered to the Beetle microcontroller

1. Cut off the through the hole connector by cutting slightly into the large folding pads. The goals is to have soldering pad up to cut edge, so that when we solder two components together the solder will flow freely across. Cut the through the hole connector from the button, both ends of one bus and a single end of the other bus.

2. Abut the edge of the cut button with the cut end of the bus with both ends cut. This is our middle bus. Apply solder across the pads.

3. Solder the cut edge of the middle bus to the cut edge of the end bus. You may want to add some hot glue over your solder as strain relief.

4. Cut 4 lengths of 4" long flexible silicone coated wire. Solder 1 strand silicon coated wire to each of the 4 holes in the end bus. Be sure to trim the wire after soldering with flush cutters.

5. Test your soldering connections with a multimeter. Select the continuity test on your multimeter and apply the test leads to the pads furthest from each other. Our multimeter makes a satisfying beep with a successful test. If the continuity test fails test each individual solder connection by apply the test leads on both side of the soldering point. Resolder any failed connections.

Step 7: Install the Loomia Electronics Into the Bag Strap.

The Loomia bus is flexible and will go in our convertible strap so the button can be accessed when it is worn as a backpack and a tote bag.

1. Using a small pair of scissors or seam ripper cut a slit in the fabric of the bag front under the sewn down strap. The slit should be long enough for the Loomia bus to fit through to the interior of the bag. The slit placement is shown as a red line in the photos. Pull the Loomia bus through at least one inch to the interior of the bag.

2. Lay the Loomia bus along the inside of the cork fabric strap. Use double sided tape or crazy glue gel to hold the bus to the inside of the strap. Do not tape or glue right on the edges because that is where it will be sewn and it will make your needle sticky if you sew over tape or glue.

3. At the end of the strap mark where the low profile button will be on the strap. Draw a circle the same size as the button and use a hobby knife or scissors to cut it out of the cork fabric. Secure around the button with glue or tape.

4. Place the single strap along the bottom of the strap so it forms a sandwich with the Loomia bus in between. As you get to the end of the bus where it enters the bag you will need to trim the sides of the strap so it fits through the slit in the bag front. Pull the bottom strap through the slit into the interior of the bag and clip to hold it in place.

5. Peel the backing off the Loomia bus and stick it to the wrong side of the bottom strap. The adhesive is very strong so take your time and place the bus carefully so it is in the center of the bottom strap. Clip in place to hold.

6. Topstitch the long sides of the strap starting from where the separated straps start on the front of the bag. Sew carefully so that your stitching is 1/8" to 1/16" from the edge of the strap. Trim extra cork fabric if needed.

7. Match the bottom of the other strap to the other top strap. Trim the start near the bag if needed to match it up. After sewing along the whole strap, trim the end so it is the same length as the strap with the Loomia Bus.

8. Add the D-rings

8a. Trim 0.25" off each side of the last 1 inch of each of the straps. Topstitch the cut edges.

8b. Place 2 D-rings at the end of the strap and fold over 1/2".

8c. Sew along the edge to finish the strap with the D-rings at the end.

8d. Repeat for the second strap.

Step 8: Assemble the Electronics

The electronics include the solar panel, the solar charger, the lipo battery, the PowerBoost, the microcontroller, and the addressable LED strips.

  1. Mount the solar panel back onto the bag. Use the awl to help get the little screws back through the bag fabric.
  2. The solar panel already has a power connector attached to it, but it doesn't matched the size of the jack on the solar charger. The solar panel ships with a 3.5mm plug but the connector on the solar charger is the standard 5.5 DC size. Luckily, there is a readily available adapter cable. Let's plug that in.
  3. The solar charger needs to have the large capacitor soldered on. The capacitor is polarized so you need to solder it correctly. The large blue capacitor has a white stripe on the side with the short lead. This is the negative lead and needs to be placed through the hole near the white strip and negative side on the circuit board. The other lead is the positive and goes into the hole marked with the plus sign. You can also bend the capacitor over so it takes less vertical space. Refer to the Adafruit tutorial for more details:
  4. Prepare the PowerBoost 1000 Basic by soldering the USB and JST-PH plug connectors. See the Adafruit tutorial for more detail:
    1. Solder 2 wires to the slide switch on two adjacent pins (it doesn't matter which ones). Solder one wire to the Enable EN pin on the PowerBoost, and solder the other wire from the switch to ground GND on the PowerBoost. This will let us turn the PowerBoost off to let the battery charge quicker.
    2. Solder a JST PH plug to the PowerBoost to power the microcontroller. Solder the red lead of the wired plug to 5V and the black lead to GND next to the 5V.
  5. The solar charger needs to be connected to the Power Boost. Both have JST-PH sockets so you will need to make a connector cable. Prepare this cable by soldering two wired JST plugs together, matching the red and black wires and covering the soldering join with heat shrink.
  6. Prepare the microcontroller by soldering the JST-SM connector for the addressable LEDs, JST-PH jack for power, as follows (see photos).
    1. The 3 pin JST-SM connector for the addressable LEDs needs to be connected to power, ground and data to a PWM pin on the microcontroller. Solder the power wire (red) through the hole (+) on the Beetle board, solder the ground wire to -, and solder the data wire to pin 9 on the Beetle board.
    2. Solder the 2 pin JST-PH power connector matching the power wire to another (+) pin and ground to another - pin on the board. There are two other wires that will also need to be added to this (-) pin.
  7. Lastly, solder the 4 wires from the Loomia bus. These connect to the Loomia lit button. The connections are from the left to right with the button on top (see photos):
    1. Left: This is the ground for the button LEDs and needs to be connected to ground (-) on the microcontroller, add this wire to the (-) pin you used for the black wire in the previous step.
    2. Center Left: This is the ground for the button itself and needs to connected to a GND (-) pin. You can add this to the the same GND (-) pin that you used for the previous wire and the black wire from the JST connector in the previous step, or add it to the other (-) pin on the board.
    3. Center Right: This is the button signal and needs to be connect to a digital pin, solder it through pin D11.
    4. Right: This is the power for the button LEDs we will connect this to digital PWM pin D10 so that we can fade the button up and down.

Step 9: Program the Beetle (Arduino)

Before we put the board in the bag we will need to program it. You will need your computer and a data USB to microUSB cable (the cable that came with your charger might just be for power. You need one that is data and power).

1. Download the Arduino IDE from If you are not familiar with the Arduino software and code we recommend you try some of the tutorials on the Arduino website.

2. You will need to add an Arduino libraries. It can be downloaded from with the Arduino IDE.

2a. Open the Arduino IDE.

2b. Using the menus at the top of the page go to Sketch > Include Library > Manage Libraries...

2c. This brings up the Library Manager. In the right hand search bar search for "neopixel". Then click the Install button.

3. Download the code from this tutorial - We've included the code as a file download with this tutorial. Arduino files need to be in a folder with the same name as the file. When you download the file here and try to open it you will get a message that says "The file "loomiaBag.ino" needs to be inside a sketch folder named "loomiaBag". Create this folder, move the file, and continue?". Click Ok and create the folder.

4. Open the .ino file in the Arduino IDE.

5. Plug your board into your computer with the USB/microUSB cable. Using the menu bar at the top select Tools. Scroll down to Board and select whatever board you are using. Then select Tools > Port from the menu bar your board should automatically show up in the port list. If it doesn't check to be sure you are using a data cable to connect your board to your computer.

6. Click the check mark Verify button. This will compile the sketch and will let you know if there are problems.

7. Click the right arrow Upload button to upload the program onto your Arduino board.

8. Unplug your board from the computer.

9. Connect your Beetle board (Arduino) to the LED strips using the JST connector.

Step 10: 3D Print the Electronics Case

We designed a snap-fit case to hold the lipo battery and three circuit boards used in this project: the solar charger, the PowerBoost, and the microcontroller. It is designed to be 3D printed on most hobby 3D printers without supports. If you don't have access to a 3D printer, a solid plastic case, like a photo case with some holes for the cables will protect your electronics.

3D print the bag using your preferred filament type and printer. We used PLA filament and an Ultimaker 2+ printer.

Step 11: Put It All Together!

1. Check that all your electronics are connected! Solar panel into PowerBoost, LED strips plugged into the Beetle board (Arduino). Put your electronics in a protective case and stow the case in the large electronics pocket.

2. A USB charging cable for your phone can be plugged into the PowerBoost and your phone can go into the small electronics pocket for protection when it is being charged.

3. Take the D-ring ends of the straps and thread them through the cork fabric loops starting at the front of the bag and then through the loop on the back of the bag.

4. Thread your strapping ends through the D rings and adjust so your straps are comfortable over your shoulders. Wear the bag as a backpack or as a shoulder tote bag.

5. Press the Loomia lit button to turn on and off the light strips and to cycle through the lighting patterns.