Introduction: Solar Necklace T-Shirt

About: My work combines conductive materials and craft techniques to develop new styles of building electronics that emphasize materiality and process. I create working prototypes to demonstrate the kinds of electron…
Neck-stroking wearable for sunny days. The components for this solar driven circuit are integrated in this decorative t-shirt, exploring the possibilities of textile electronics and interaction with the sun.

Following the example of the Wearable Piano Interface this Instructable is made to accompany a workshop titled "Build your own interactive t-shirt" that will take place on the 1st January 2009 in Basel, Switzerland at the gallery.

The workshop takes place during the Ying Gao exhibition at and for the first time we experimented with the use of solar cells, motors and motion in wearables. So this workshop will be a mix of our regular methods and some new techniques that we hope won't fail us. Smile.
Link to workshop

The circuit and this project were inspired by the Overheadbots which we saw at the workshop they gave at the DIY Festival in Zurich 2008. Thank you very much!

The complete circuit that harvests the energy from a 0,5V 100mA solar cell, storing it in capacitors and then releasing it to drive a motor, is split up into modules and integrated into a t-shirt.

The solar cell (which can also be replaced by a 3V button battery) is combined with two capacitors in a necklace that can be attached and detached from the t-shirt via poppers.

The motor (a force-feedback motor taken from a Playstation controller) is situated on the shoulder, and is also connected via poppers. The force-feedback is removed and replaced with a feather that strokes the neck of the wearer every time it turns full circle.

The remaining components are soldered together to a cluster (maintaining the correct circuit connections) and sewn to the t-shirt directly. Optionally this module could also be made removable or even encapsulated in resin, making the t-shirt fully machine washable.

The final part of the circuit are the conductive traces that connect the components in the individual modules. These traces are made by fusing (iron-on) strips of stretchy conductive fabric directly to the t-shirt. The traces can finally be isolated using stretchy fabric glue. This keeps them from coming loose as well as stopping short circuits or otherwise unwanted connections caused by folding of the fabric.

This is only an example of what is possible. In the workshop, participants will also be introduced to Fabric Buttons and switches, and especially encouraged to experiment with the motor output (see step 9).

Follow this link to see pictures of the workshop >>


Step 1: Materials and Tools

>> also see
>> also see
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  • Fusible interfacing from local fabric store or from
  • 1,5mm thick neoprene from
  • Hook-up wire for hooks and loops
  • Poppers from local fabric store
  • Small piece of non-stretch fabric as backing for poppers
  • Motor taken from a Playstation controller (vibration force-feedback motor with ungewicht)
  • 3V Button battery
  • T-shirt
  • Regular thread
  • Beads

All components from

  • BC556B Transistor
  • BC546B Transistor
  • LED or diode
  • 2200mF Capacitor
  • 1000mF Capacitor
  • 1 K Ohm Resistor
  • 2,2 K Ohm Resistor

Solar cell:
UNFORTUNATELY the solar cells that we ordered for the workshop (model# 1-100, 0,5V 100mA, 3.50USD/each) are not strong enough. We are looking into getting replacement cells from a company in Europe, which we will send you.The following solar cells from Conrad should work, but no guarantee until I've tested them >>

Optional Materials''
  • Scissors
  • Sewing needle
  • Soldering iron, solder and helping hands
  • Wire strippers
  • Wire cutters
  • Two pliers for undoing popper mistakes (pulling them apart)
  • Rounded tip pliers for curling wire into hooks and loops
  • Popper machine
  • Pen and paper
  • Multimeter

Step 2: Solar Cell and Capacitor Necklace

If your solar cell does not already come with some kind of wires attached to the + and - poles, then you'll want to solder two short wires with little loops at the end to these before you start.

Start by making two little hooks with a loop on the opposite end, by bending wire around your pliers. See photos. Or you can use any small metal hooks that you have.

Now thread a small (so it will fit through the beads) needle with conductive thread. Take it double. Stitch through one of the loops of the hooks you just made and fasten it. Now start stringing beads onto this thread. As many as the length of your first capacitor, plus a few more. In my case it was 20 beads. Make loops with the wires of your capacitors (no need to solder them) and sew around the loop of your capacitor a few times before continuing to thread beads onto the string. Again use enough beads to cover the length of your second capacitor, plus a few more. When connecting the second capacitor make sure that if you sewed to the minus leg of the first capacitor that you do the same for the second. Now do the same for the other side, connecting the plus sides together. See photos.

When you have finished both sides and both are equally long. Cut two small droplet shape pieces of neoprene (you can also use another kind of sturdy fabric). Fuse a strip of conductive fabric one side of each of these droplets. Sew one of your beaded conductive threads to the narrow end of one of these droplets. Connecting conductive thread with conductive fabric! And sew beaded conductive thread to the narrow end of the other droplet. See photos.

Now punch poppers through the wider end of each of the droplets.

Step 3: Motor Pouch

In order to be able to fasten the motor to the t-shirt we need to create a little neoprene pouch for it (again you could also use another kind of sturdy fabric instead of neoprene). And the pouch has to connect both motor contacts to the outside (poppers).
First start by isolating the shell of the motor with a strip of isolation tape. Then strip about 2 cm off both motor wires. Now, on opposite sides of the motor, tape the ends of the wires underneath 1 x 0,5 cm pieces of copper conductive tape with conductive adhesive.
Now you'll want to cut a piece of neoprene that is as high as your motor and about 1cm shorter than the circumference. This will make the pouch tight enough to hold your motor in place. Don't forget to add two evenly spaced tabs - so that when you close the circle, the tabs stick out at opposite sides. See photos.
On the inside of the neoprene fuse two pieces of conductive fabric so that they will make contact with the pieces of copper tape and reach all the way out to the end of each tab.
Now sew the neoprene pouch together and add two poppers to each tab. Place the motor inside and make sure that the copper tape lines up with the conductive fabric. So far it does not matter which side of the motors goes where, as it only changes the direction the motor is turning.

Step 4: Circuit Broach

I'm not sure if I found a good solution for this module of the circuit. I decided to solder all the components together without using a perfboard and without spacing them apart. It does give for a nice tight shape and interesting broach-type look. But it is also a bit confusing to explain in words. Basically you want to follow the circuit diagram and solder little loops to the following three leads so that they can be connected to the other circuit modules: + (plus), - (minus or ground) and the second connection that runs to the motor.

Please take a good look at the circuit diagram and the photos to see how to connect all the components and let me know if I am being unclear and I will try to explain more clearly.

Step 5: Conductive Traces

Now that the three circuit clusters are completed (power, motor outputs and components) we need to create the network of conductive traces that will connect them with each other.

  • The + from the solar cell needs to connect to the + loop of the component cluster broach, as well as to one of the sides of the motor.
  • The  from the solar cell needs to connect to the - loop of the component cluster broach.
  • The M leg from the component cluster broach needs to connect to the other side of the motor.

Using a fabric pen (one that will disappear over time) you can trace these paths onto your t-shirt before fusing the conductive traces.

When you order stretch conductive fabric from LessEMF it does not come with the heat fusible interface attached. The fusible interface that you can buy from your local fabric store normally comes attached to a sheet of wax paper. The easiest way to make conductive traces is to fuse a long strip (the length of your conductive fabric and maybe 10 cm wide) to your conductive fabric. You do so by placing the interfacing (way paper side up) on top of your conductive fabric and then ironing it on. You'll want to experiment with a small piece of conductive fabric first to find the right temperature on your iron settings. The conductive fabric will burn if it is too hot. But it is normal if it discolours to become more golden to some extent. It become brittle the more it is burnt. You want it to stick well but not get too golden. Once you have fused the fusible to the conductive fabric. Pull of the way paper and cut the conductive fabric into long 1-05 cm wide strips. And now you can fuse these (interfacing side down) to your t-shirt. Again be careful to get the right temperature. You can use stretchy fabric glue to isolate and better attach these traces to your t-shirt, but it is best to do this at the very end, when you have checked that everything is working, and also because it takes a day to cure.

Read the instructions on your popper machine and connect poppers at the right ends of the conductive traces for the solar necklace and the motor. You might want to add little patches of non-stretch material behind the poppers (on the inside of the t-shirt) to reinforce the t-shirt fabric, because it rips quite easily when pulling the poppers apart.

Step 6: Battery Pouch

The battery pouch is not necessary. The idea is that it can replace the solar cell on cloudy days. Simply hook it onto the hooks at the end of capacitor necklace module, where the solar cell normally hangs. Of course you can also directly connect it to the motor, the battery current does not have to pass the capacitor and amplification circuit.

Cut two rectangles of neoprene the diameter of your button battery and about 1 cm higher. Round the corners. Fuse a strip of conductive fabric to either side, diagonally so that they will only cross in the center when you lay them on top of each other facing each other. Because one side (the minus pole) of the button battery is rounded around the edge, it might end up touching both sides and this is why you want to isolate the conductive strip that will be touching the plus pole in this area. See photos.

Using conductive thread, sew two loops to the ends of each piece of conductive fabric so that they will stick out and can be attached to the same hooks that otherwise hold the solar cell. You can either make the loops yourself by winding some hook-up wire around your pliers and soldering them or otherwise buy some.

Sew the pouch together. If you like you can mark the plus side. In my case with a red bead.

Step 7: Test

Now that all the component modules are finished and the t-shirt too, you'll want to plug (popper) everything together. And hope that it works.

Best to test with a battery first. Make sure it is fully charged. The LED should light up slightly and then extinguish as the charge goes to the motor. And the motor should turn a few times. The amount of charge depends on the capacitor and the duration for charging depends on the strength of the battery or of the sun in the case of the solar cell.

See video (coming soon...)

Step 8: Feather

If everything works then now is the time to mount the motor output. In my case I decided to simply horizontally attach a feather to the motor, so that every time it turns, it strokes my neck.

Step 9: Tips, Improvements

Motor pouch
The conductive fabric strips in the motor pouch tend to make contact with the metal casing of the motor, short circuiting the current. To avoid this problem you can isolate you whole motor casing with electrical tape. See photos.

3V Button battery pouch
The 3V button batteries are not very strong for driving a motor, especially if there is a longer stretch of conductive fabric in between it and the motor. Try mounting the button battery close to the motor and directly - not via the capacitors or amplification circuit cluster. You can add a [http://Fabric Button] to one of the leads leading from the battery to the motor so that you have control over when the motor moves and when not.
Another good option is to make a double AA battery pouch or two single AA battery pouches, instead of the button battery pouch. Two AA batteries have much more power to move the motor and will last longer.