Introduction: Joy Slippers Version 2
Visit the JoySlippers website >> http://www.joyslippers.plusea.at/
This Instructable improves upon the previous version https://www.instructables.com/id/Joy-Slippers/.
It will show you how to make a pair of Joy Slippers, connect them to an Arduino physical computing platform and run a Processing application that will allow you to draw with your feet, as seen in the following video.
The resistance range of the pressure sensors depends a lot on the initial pressure. Ideally you have above 2M ohm resistance between both contacts when the sensor is lying flat. But this can vary, depending on how the sensor is sewn and how big the overlap of the adjacent conductive surfaces are. This is why i choose to sew the contacts as diagonal stitches of conductive thread - to minimize the overlap of conductive surface. With the pressure sensors inside the JoySlippers, the initial pressure from simply wearing them, brings the resistance down to about 2K ohm and then when fully pressured by standing on the foot it goes down to about 200 ohm.
The next step (for me) is to find better applications for the Joy Slippers. The videos of the drawing application show that certain motions create certain patterns, meaning that they can be tracked.
I'm experimenting with some ideas for applications that make use of this and would appreciate any feedback, comments, ideas...
For more videos visit the YouTube Joy Slippers playlist
For more pictures visit the Flickr Joy Slipperes set
The materials that you will need are simple, but it's probably not all stuff you have lying around your house. It comes cheap if you plan on using the materials for future projects, especially if you are interested in wearable technology or soft circuits.
So, how does it work?
The layering of conductive and ex-static in the slipper's soles creates very very simple variable resistors that are pressure sensitive. The layer of ex-static plastic between your conductive thread patches allows for more current to pass through, the harder you push the conductive layers together. I'm not 100% sure why it works, but it does, and it is amazingly stable. So by shifting your weight from left to right and tiptoe to heel you can generate pretty much every direction.
For up-to-date information visit the project website >>
Step 1: Materials and Tools
MATERIALS for the Joy Slippers:
- Conductive thread - 117/17 2ply (17USD from www.sparkfun.com)
- Ex-static - plastic from the black bags used to package sensitive electronic components
- 6 mm thick neoprene with jersey on both sides (ask at a local surf shop for leftovers, or if you live in Europe and plan to use neoprene for other things, get a sheet from www.sedochemicals.com)
- Stretchy fabric (you can also use a pair of old socks if you don't feel like sewing so much)
- Regular thread
- Perfboard with copper line pattern (7x3 holes 6.25USD from www.allelectronics.com)
- 50ft Spiral telephone wire (1.99USD at 99cent store)
MATERIALS to make Arduino connection:
- 4 x 10K Ohm resistor
- Perfboard with copper line pattern (6x6 holes)
- 15cm of rainbow wire with 6 cables
- 2 telephone jack outlets (5 for 1.50USD at 99cent store)
- Tupperware box or similar
- Arduino USB Board (35USD from www.sparkfun.com)
- USB cable (4USD from www.sparkfun.com)
- Laptop or computer (hopefully you have one, or can borrow one)
- Processing installed on your computer (download free from www.processing.org)
- Arduino software installed on your computer (download free from www.arduino.cc)
TOOLS you will need:
- Sewing needle
- Pen and paper or cardboard
- Your feet
- Multimeter for checking your work
- Soldering iron
- Third hand
- Pliers or some kind of wire cutter
You will need to be able to solder. Soldering is not hard and there is a nice Instructable right here: https://www.instructables.com/id/How-to-solder/
You will need to know how to use the Arduino software environment, in order to upload following code to your microcontroller. It will read the first 4 analog inputs and receive them via USB.
Following Processing application will read the incoming values from the Arduino's inputs and use the information to draw a line.
Input will be read as follows:
Analog INPUT  = Right foot TOES
Analog INPUT  = Right foot HEEL
Analog INPUT  = Left foot TOES
Analog INPUT  = Left foot HEEL
_080209_JoySlippers_etchAsketch.zip www.plusea.at/downloads/ _080209_JoySlippers_etchAsketch.zip
Step 2: Pattern Making and Tracing
Making a stencil
Because everybody's feet are different you are going to have to decide who to make these Joy Slippers for.
This Instructable will only go through the steps of creating the right slipper. The left slipper is exactly the same, except you will have to turn the stencils upsidedown.
Trace your right foot onto a piece of thin cardboard or thick paper. Before cutting out the tracing draw a tongue-shaped tab that sticks out from the heel about 5cm (see pictures). We will call this the tongue and it will be where we attach the slippers to the electronics later on.
Now cut out the tracing with the tabs. Put your foot back on the tracing and find the areas where:
1) your heel presses
2) the balm of your toes press
In these areas you will want to draw a strips of 1.5cm wide and at the toes: 6cm long and at the heel: 4cm long. Make sure these strips do not come within at least 1cm of the edge. Cut out the insides of these strips and make markings every 1cm along the lengths. In the next step these strips will make sense.
Tracing onto neoprene
Trace these stencils on to the neoprene twice for one foot. And mark everything as shown in pictures.
Tracing onto ex-static
You do not need to make a separate stencil for the ex-static, unless you plan on making more than one pair of slippers.
Trace the foot stencil onto the ex-static and cut it out about 5mm smaller all-round. Do not include the tongue.
Tracing onto stretch material
Unless your foot is exactly the same size as mine (European 39) then you will have to alter the pattern as seen in picture. You can also sew on a pair of socks and save yourself some time.
Step 3: Sewing Inputs and Vcc
Thread a needle with enough conductive thread. Take one of the pieces of neoprene, this is going to be the Vcc, the power supply for the sensor where the 5V from the Arduino will run to. Tie a knot in the end of the thread; do not take the thread double. From the back (in my case black side) poke the needle through the neoprene at one of the end dots of the toe strip marked from the stencil. Stitch back and forth in a diagonal zigzag manor until you reach the other end of the strip. From here go bring the conductive thread back to the back side of the neoprene and make small stitches on the back towards the tongue. When you reach the tongue you can stop sewing and without cutting the thread remove the needle and continue with the following.
Inputs: Toes and Heel
Take the other piece of neoprene. Essentially you will do the same here with one exception: You will sew the zigzag pattern opposite to the way you sewed the Vcc strips! This way, when you lay the pieces of neoprene on top of each other, conductive thread zigzags facing inwards, they will crisscross each other and make for a good connection. Take a good look at the pictures.
Before going onto the next step, now would be a good time to check your connections using a multimeter. Measuring from the loose ends of conductive thread, check for a connection between any of the three ends. There should be NO connections. If there are, then you probably accidentally crossed conductive threads somewhere along the way. You can quite easily pull out the conductive thread and start over again.
Step 4: Finishing Slipper
Sewing sole of slipper
Now you will want to layer you pieces as follows so that the conductive traces are facing inwards:
- Vcc or Inputs
- Inputs or Vcc
Hold everything in place and stitch around the edges of the neoprene. Sewing both layers of neoprene together, not including the ex-static in your stitches. Take a good look at the pictures to see how to best to stitch. Do not sew the tongues together (yet), instead stitch back and forth at the foot of the tongue, giving it a bit of a dent and making it easier to bend later on.
Another multimeter test
You can now make another multimeter test to make sure none of your inputs and/or Vcc are touching each other. You should have some resistance between the inputs and the Vcc. And this resistance should become less when you apply pressure to the top of the layers. What you don't want is a permanent connection. Or no connection at all between an input and Vcc. Or any kind of connection between the inputs.
Decide left or right
NOW you really decide if this is going to be the sole of a left or a right slipper.
Take a cutter and cut just a very very small slit into one of the tongues. The tongue you cut the hole in will make it the outside layer of neoprene, the one the touches the ground, not your foot.
Take the 50ft spiral telephone cord and cut it in half. We will use one half for each slipper. So we only need one at the moment. From the cut end, strip away about 2cm of the thick insulation
To bring the conductive thread and wire together we need to solder three of the four wires to a small piece of perfboard. 4x7 holes with 7 strips of conductive copper pattern. I double-spaced the wires to make double sure I don't get any connections between the conductive threads. Please see illustration image for how to solder and sew. Also see the illustration for which three of four wires you should pick to solder.
Now that the conductive threads are connected to the wires of the telephone cord you can stitch around the tongue, enclosing it all between the two layers of neoprene.
If you choose to use a sock instead of design your own slipper then now you will be attaching the neoprene sole to your sock. Instead of socks, you can also attach straps of fabric, anything that will hold the sole firmly to the bottom of your feet. If you don't want to sew at all, you can try wearing the soles inside some socks or even shoes!
To follow the pattern shown in the pictures, take the pieces of stretch material and sew them right-sides-together to the edges of the sole (upsidedown). Follow the images to get an idea of how to sew the pattern together. Attach the tongue to the heel so that is sticks up and stays in place.
Step 5: Making Connection to Arduino
This step shows how to make the connection to the Arduino. For this you will need an Arduino, which is a physical computing platform that has a USB connection to your laptop, contains a microcontroller that we can program to read the variable resistance of the Joy Slippers from its analog inputs.
Of course, if you know what you are doing, you can hook the slippers up to any other circuit or device you have for making use of their variable resistance. So if you don't intend to hook the Joy Slippers up to the Arduino, then you can skip this step.
The connection from the slipper consists of:
- Two male telephone jacks coming from the slippers
- Two female telephone jacks that will be attached to the Tupperware box
- Inside the Tupperware box the Arduino inputs will connect to the back side of the female telephone plug socket and there will be a small circuit that puts a 10K Ohm resistor between each input and the ground.
We need two female telephone jacks. You can dismantle a telephone jack adapter for this. You might want to clip the wires sticking out at the back to about 5mm length so that they don't come so close to each other.
You need to cut three holes in the Tupperware box. Two for the female telephone jacks and one for the USB Arduino cable. Use a cutter or a drill and be careful.
1) Follow semantic and solder rainbow wire from headers to perfboard with resistors, to more rainbow wire.
2) Poke the ends of the telephone wire out through the hole of the box and solder them to the female telephone jacks according to the semantic.
Once the female jacks have been soldered you can superglue the jacks to the box to make them sturdy and relieve all strain from the wires.
Now the box is finished and you should decorate it if you can.
Step 6: Hooking Up to Your Computer and Running the Drawing Application
Make sure everything is soldered together correctly and all the plugs are in place.
For Arduino microcontroller code and Processing visualization code please look here >> http://www.kobakant.at/DIY/?cat=347
Because each slipper is individual and depending on all the exact materials that you use and the way you sew them together, the range of variable resistance will be different for each sensor (right toe, right heel, left toe, left heel). This is why there is a threshold function in the processing applet, that allows you to set the MIN and MAX values of your sensor. These will be between 0 and 1023.
MIN threshold should be slightly above resting state and MAX threshold should be maximum value obtained when pushing as hard as possible on the Joy Slippers.
I'm currently developing different applications and games for the Joy Slippers.
For up-to-date information visit the project website: http://www.plusea.at/projects.php?cat=1&work=14
Although this is the second version, I'm still thinking about improving and would appreciate any feedback you can give me after having read though this Instructable.
Thanks and enjoy