Repurpose a dollar-store bicycle safety flasher to embed in the scarf. Simulates the light changing pattern and does other fancy sequences. No arduino needed.
The technology is borrowed from the earlier Lithium Rain Radiant Beacon of Righteousness (Blinking I-hoodie).
Step 1: Stuff to Make It
You can use any soft fabric that doesn't stretch too much as long as it is comfortable to touch when you wear it.
You need something that equates to a strip of fabric about 12" wide by 60". The fabric is doubled over lengthwise for a finished scarf width of about 6 inches. It can be shorter or longer as you like.
Use remnants to piece together the scarf for a more varied look.
The electronics in this scarf is based on a dollar-store bicycle safety flasher. It is a self contained unit to house the batteries, has a switch to cycle the light patterns and contains 5 red LEDs.
You will need to mod it to add yellow and green LEDs. Some flashers may have all white LEDs which you can adjust by the filter material but you will still need to mod the flasher unit to extend the LED from the circuit board. Soldering skills are required.
You will need some clear plastic adhesive shelf liner paper.
You will need a plastic shopping bag in red, yellow, and green to use as color filter material. Come to think of it, none of them are really "green".
You can hand sew this but a sewing machine is much more efficient. I also use a serger which is great for simple projects like this.
Step 2: Mod the Blinker
Since they on the circuit board, the LEDs need to be desoldered and extention wires added.
LEDs need to be wired up to the correct polarity in order to work. Figure out if the larger piece inside the LED goes to hot or positive and solder it. If it doesn't work then you have to switch the leads. It is hard to tell with diffused LEDs or leads that are already clipped off.
These cheap import units seem to use some junk quality of solder on them because it seemed to flake off and was grainy when heated up to pull out the LEDs. I had difficulty in resoldering new wires since the slightest application of heat seemed to pull off the original copper trace on the circuit board. I had to scratch the resin coat to expose some copper in the surrounding area on that trace in order to connect the new wires.
I had an assortment pack of LEDs from the Shack so I had to find the similarly rated LEDs to replace the ones I pulled out. White light LEDs seemed to draw to much power and did not work. I was finally able to get the tinest LEDs - green and yellow - to work as replacements.
I had planned on a color scheme of red, yellow, green, red, yellow. Three LEDs to simulate the traffic light and the other two for a walk/don't walk sign.
Step 3: Cut to the Chase
I made up a graphic 2" x 4". It can be anything you want. One side will blink red and the other yellow.
Laminate the graphic with the clear plastic adhesive shelf liner paper.
Cut it out a little larger to give it a border to sew around.
CAUTION: Know the capabilities of your sewing machine. Sewing materials other than fabric probably voids your warranty. Broken needles can occur if you try to sew something not intended to put through the machine. Always experiment on your mom's sewing machine first.
Double the fabric lengthwise to see where you will be creating the stoplight.
The final product is sewn like a tube that is turned inside out.
Position your graphic on the backside of the piece near the bottom of your scarf.
Sew a straight seam to outline your graphic.
On the finished side, pinch the area inside the sewn boundary. Clip it so you have a hole to poke the scissor in to cut the fabric out.
This should expose the graphic. Trim around the inside edges.
Go over with some kind of zigzag stitch to give it a finished look.
Step 4: Hole in One
I traced the inside of my roll of masking tape. It seemed about the right size.
Draw on the back of your adhesive shelf liner paper. Make sure your know which side is which. You want the peel-off backing facing you and that is what you write on.
Position on the backside of your scarf with the plastic good side down on the fabric.
Sew around each light.
Clip in the front and trim around the inside edges.
You can sew once more around with a zigzag stitch to give it a more finished look.
On the back, peel away the inside of the circles for the lights.
Cut out filter material from plastic shopping bags in the appropriate color. I didn't have any green ones to use.
Cut out a piece to stick to the exposed adhesive. Red on top light, yellow in middle, and green on the bottom light.
Trim any excess filter material from around the lights.
Cut out another piece of clear shelf liner to "laminate" all three lights.
Step 5: Pad It Out Just Like Corporate Expenses.....wait
I had box of wet-wipes that had gone dry. I also had some polyester fiberfill batting.
I found I could make something like my coffee pods with two layers of wipes sandwiching a core of a bit of fiberfill would make a decent diffusing medium.
Sew around with a zigzag stitch.
Trim off the excess.
Put a seam down the middle of the walk/don't walk graphic to separate the light transmission.
Put some tape on the back of the diffuser pads and punch a hold with an awl or utility knife to fit the LEDs.
Tape up the LEDs so the wires would not short out if the leads are bent when pushed into the diffuser pad.
Step 6: Serging Ahead...
This would be a pocket sewn on the inside to hold the flasher unit in the scarf.
I serged the piece to elongate my traffic light portion of the scarf to final length.
I serged the both ends since I wanted a finished look even though the ends of the tube would be open. You need the opening to reach in to initially place the electronics or change batteries.
Seam along the side to form the long tube.
Turn the tube inside out to see if you like the look of the finished scarf.
Fleece can be difficult to feed through the machine smoothly so some places might be a little uneven.
Partially turn the scarf inside out again so you can place the LEDs in and tape them into position.
Place the battery pack in the inside pocket.
Smooth everything down.
Lights, camera, action!
CAUTION: Wear everywhere except near modes of public transport.
I was going to have that CAUTION tape striped ends with red/white but I did not have that fabric.
You could add reflective tape to make this a real safety scarf.
You could adapt this for true soft circuit definition by using conductive thread.
You could adapt this for arduino for more realistic light patterns/timing or reaction to sensor input.
You could use EL panels or rings of EL glow-wire to light it up.
Make one and have fun with it! Go out and play in the street.