Soft-sensor-saurus | an E-textile Soft Sensor Soft Toy With LED Light

Soft-sensor-saurus is an interactive e-textiles soft toy. It has an embedded pressure sensor and an LED globe. When you give the dinosaur a squeeze, its heart lights up! This projects is an approachable introduction to e-textiles and wearable technology for beginners to electronics. Basic sewing skills are required. No soldering or coding is required.

Materials

• 40cm x 40cm woven cotton or fleece fabric
• 10cm x 10cm felt
• 15cm x 15cm x 15cm polyfill
• Googly eyes
• 50cm conductive thread
• 1m conductive yarn
• Mid weight knitting yarn
• 2 x AAA batteries
• 1 x (2 x AAA) battery case with switch
• 1 x 10mm round red LED 270mcd
• Sewing thread

Equipment

• Sewing machine
• Fabric scissors
• Scissors
• Hand sewing needle with large eye - suitable for embroidery
• Sewing pins
• Wire strippers
• Needle nosed pliers
• Hot glue gun
• Knitting nancy
• 2 crocodile clips
• Iron
• Ironing board
• Permanent marker
• Pencil

• Cut out pattern pieces from paper
• Cut base fabric pieces:
• 1 x front
• 1 x base
• 2 x sides (mirrored)
• Cut felt fabric pieces:
• 1 x nose
• 1 x belly
• 5-6 x spines
• 4-6 spots

• Place first side piece on the table with fabric right side up
• Place triangle spines on top of side piece, pointing away from the spine edge
• Stack second side piece on top, with fabric wrong side up
• Pin
• Sew 3/4 cm seam along spine
• Invert back piece so that triangle spines are pointing outwards
• Iron flat

• Lay base piece flat on table with fabric right side up
• Fold base piece as shown so that the round front section is stacked in a triple layer
• Sew a 1/2 cm seam around the base, creating a pocket opening
• Iron flat
• Cut a small incision (1/4 cm) at the bottom of the pocket
• Place 2 x AAA batteries into battery case
• Push battery wires through the incision at the base of the pocket and push battery case into the pocket

• With right sides together, pin one side of the base to the bottom of one of the side pieces
• Sew together with a 1/2 cm seam allowance
• Pin the other side of the base to the bottom of the other side piece
• Sew together with a 1/2 cm seam allowance
• Remove battery case and iron seams flat
• Replace battery case

• Lay belly onto front piece as shown
• Use the buttonhole setting or a narrow zigzag stitch to applique the belly to the front piece. Only sew the bottom half of the belly
• Baste around the outside of the nose piece and pull together to create a 3D shape
• Place a small amount of polyfill inside the nose
• Applique nose to front piece
• Place bottom of front piece and bottom of base with right sides together, and pin the centre of both pieces together

• Follow the knitting nancy tutorial outlined here
• Hold the mid weight yarn and conductive yarn together and knit as if they were a single thread
• Continue knitting until you have a piece around 5cm long
• Alternatively, knit one long strand then cut into pieces. Use a sewing machine to sew the ends of the knit sensor closed.

• Remove the battery case from the fabric pocket and switch off.
• Use wire strippers to remove the rubber coating on the wires on the battery case so that around 2cm of the copper is exposed
• Twist the ends of the battery wires into loops
• Identify the longer leg of the LED globe. This is the positive leg. Mark it with permanent marker so you will be able to identify it later
• Use crocodile clips to connect the circuit as shown. Connect the red (positive) battery wire to the positive leg of the LED. Connect the other leg of the LED to one end of the sensor. Connect the other end of the knit sensor to the black (negative) wire of the battery.
• Switch the battery case on. You should see a faint glow from the LED. When you compress or stretch the knit sensor the LED should glow more brightly.

• Place the LED globe on the front fabric piece of the dinosaur approximately 1cm down from where the top of the belly felt will be attached.
• Poke the two legs of the LED through the fabric piece. Use two separate holes so that the legs of the LED do not touch.
• Identify the positive leg of the LED and use a pencil to mark the fabric with a + symbol next to the positive leg.
• Use the needle nose pliers to bend the LED legs out to the side.
• Then grip the end of each leg with the pliers and rotate the pliers to roll the legs up into a coil.
• The coils should lay flat against the surface of the fabric.
• Reinsert the battery case into the fabric pocket at the base of the dinosaur and pull the battery wires through the small incision at the base of the pocket.
• Loop the end of the red wire onto the positive leg of the LED
• Use conductive thread to stitch the red wire and LED leg in place. Use 5-10 stitches on top of one another to form a strong connection

• Insert sensor between belly felt and base fabric
• Use conductive thread to stitch the top of the sensor in place and then to connect to the negative leg of the LED
• Use conductive thread to stitch the bottom of the sensor in place and then to connect to the loop at the end of the black battery wire.
• Tie off the conductive thread with a knot and then trim any excess to prevent loose strands from touching and forming a short circuit.

• Unfold the belly felt and mark the inside where it touches the top of the LED
• Use the tip of the scissors to drill a hole into the felt
• Push the LED through the felt
• Use a zigzag or buttonhole stitch to finish sewing around the outside of the belly felt, enclosing the sensor.

• Line up the centre top of the front piece with the spine seam, right sides together
• Pin the sides of the front piece to the side pieces and sew together with a 3/4 cm seam allowance
• Leave a 5cm opening for inserting the stuffing

• Stuff the dinosaur with polyfill, using a pencil to push the polyfill into the tail then the body.
• Experiment with different densities of stuffing to make sure the sensor stays responsive

• Pin and hand stitch the opening closed

• Use a hot glue gun or craft glue to attach the eyes, spots, and any other decorations

Give your dino a squeezy hug and watch its heart light up!