How to Make a Traffic Light SmartBand
We've seen traffic light cups in a few schools now, where students put a green, amber or red cup on their desk to inform the teacher whether they understand what they've just been taught. Despite being low tech and low budget, anecdotal evidence shows that there might be a reluctance to use them as they are so visible to peers. Enter...SmartBand


SmartBand is a high tech solution to the problem, and can actually be made in schools by students. The bands are discrete but visible to the teacher.


The band is made from fabric and uses easy sew LEDs and magnetic switches to complete one of three circuits, lighting the relevant colour LED.


The soft battery pocket is secured with a snap fastener to give easy access to the coin cell so that it can be changed. SmartBand is very easy to make, but requires a basic knowledge of textiles and circuits. We got the team behind the SmartBand to create a step by step guide for you to make your very own, so without further ado:

Learn how to:

  • Make an e-textiles product from scratch.
  • Create and use a soft battery holder.

Level of difficulty:

  • Intermediate. Requires basic textiles skills – hand sewing, machine sewing, CAD design skills, and a basic understanding of simple electronic circuits.

Parts List:

In order to make your own SmartBand you will need:

You will also need the following equipment:

  • Large eye e-textile needle.
  • Sewing machine.
  • Iron.
  • Chalk.
  • Fabric Scissors.
  • Laser Cutter (Optional).
  • 3D Printer (Optional).
  • Overlocker.
  • Hand drill.
  • Multi-purpose glue.

Step-by-step guide to making a SmartBand

Step 1


If you have access to laser cutter you can laser cut the fabric for a clean, accurate finish.


The top felt layer should have three sets of holes, one set for the LEDs, one for the magnets and one for the coloured felt indicators.


The other felt layer should not have any holes in it. The cotton layer can have a very fine engraved circuit line in it.

If you don't have a laser cutter these can all be carefully cut by hand.


We've provided a simplified circuit diagram above to help explain how the circuit is laid out.


Overlock the edges of the cotton layer to stop it fraying.

Step 2

traffic_light_smartband_08_560 Using fabric scissors, cut up three small squares of felt, one red, one blue and one green. Glue these pieces to the inside of the top felt piece, directly under the three circles in the order green – blue – red.


Glue the hook and loop fastener onto each of the felt pieces. The soft side should go on the right edge of the top piece and the hook side should go on the left edge of the base layer.

Step 3

traffic_light_smartband_10_560 Using the sewing machine load up the bobbin with conductive thread.


Sew the circuit lines onto the black cotton.


Step 4


Hand sew the soft battery holder (see here for instructions to make one) into place. traffic_light_smartband_13_560 Hand sew the LEDs and switch magnets into place using the conductive thread, making sure the positives and negatives of all the components are correctly placed.


Insert a battery into the holder and test your circuit.


If your LEDs do not light up then refer to our fault finding guide.

Step 5


Place the circuit fabric within the top and base felt pieces and mark where the popper button will go according to the location of the battery holder. This is so that the battery can be changed.


Hand sew the poppers on using non-conductive black thread.


To ensure the circuit doesn't move around within the wristband, bondaweb the cotton fabric to the base layer of felt.

Step 6

Note: If you don't have access to a 3D Printer it is simple to create this piece from normal fabric and connect it to the SmartBand using a strip of conductive fabric.


Design a case for the magnetic switch and print with black ABS plastic using the dimensions 11mm x 15mm. Glue the magnets into place.


Drill a hole into one of the short side edges for the black cable using a 2mm drill bit. Cut a piece of black plastic coated wire (about 8cm long). This will be the cable that attaches the magnetic switch to the wristband. Glue one end into the hole of the case.

Step 7


The final stage is to sew the top and base layers of felt together, making sure that there is a section left unsewn for the popper button and that a small part of the switch cable is inserted directly under the blue LED so that it is secured once sewn. Use a small straight stitch to ensure a neat, visually appealing finish.

Step 8

Wear your new SmartBand knowing that if you're stuck you can discretely catch your teachers eye.




This Kitronik University Course was produced by students of the NTU Subject Knowledge Enhancement (SKE) course, a course for graduates with a degree in a subject other than D&T, who wish to train as secondary Design and Technology teachers. You can see our write up of their final presentations here. We'd like to thank all of the students for their hard work over the seven week course, and wish them all the best in their future careers.

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