http://vimeo.com/37904951

The four faces are divided into 3 sensors. The following diagram maps out the routes of the positive and negative currents and how they hook up to the input / output pins on the Lilypad arduino.

Faces 1 + 2 (F1 + F2) share a positive circuit which together go into input A2.

Likewise, F3 goes into A3 and F4 goes into A5.

The resistances for each of the sensors share a similar range: approx. 1000 ohms when at rest and 16 ohms when touching.  Therefore, the voltages range from 4.86volts when at rest to 4.99volts when activated (nearly the full 5volts of power that comes from my computer).

The arduino code was written such that when the piece is twisted (and the resistances dip below 600 ohms), LED 1 + LED 2 turn on. Similarly, LED 3 and LED 4 also turn on, but blink … with LED 3 blinking twice as fast as LED 4.

http://vimeo.com/37905341

What I find interesting about this particular project is the variability of the twisting motion. Whereas the spandex does seem to fold in similar fashion every time, it isn’t reliably consistent. Not only that, but a twist to the right does not produce the same results as a twist to the left. As such, the sensor then becomes the means by which to test whether certain areas of a stretched fabric are coming into contact when twisted. And by locating sensors in several places across the surface, you can obtain separate readings for each of the areas / sensors by programming a different LED response.

Here is the code written with Emily’s excellent help (yay!):

I used three sheets of velo-stat, a second hand lunch jacket, 1/4″ green felt, 4 LEDs, 1 lillypad, conductive thread, 6 buttons, and a spool of rainbow thread. The result is a spring wear jacket that can enliven a lecture, conduct an orchestra, or be the live of a late night faculty dance party.

The Sensor changes from 400 Ohms, to 200 Ohms, to 80 Ohms, designating the degrees of flexure. More nuanced designs can be produced for custom elbow use.

Here is the Video of its Debut:

IMG_0551

I love felting – all you need to create a tight fabric of felt is roving wool, hot water, and soap (and a lot of rubbing). When I saw a felted pompom pressure sensor during class, I was excited at the possibility of felting my own sensor.

But Arduino coding was quite new to me. I started testing with Arduino code, and made a temporary sensor/LED/lilypad combo on a piece of foam to understand the circuit layout. Sensor is made using layers of velostat, conductive thread, and conductive fabric. Tack down all parts on the foam with push pins, connect them with conductive thread, upload the code, and voila! LEDs started to blink! The arduino code makes the LEDs blink at a slow speed when the sensor is at resting state, and the speed picks up as you press/bend the felted sensor.

In this project I attempted to fabricate my own silicone rubber flex resistor.

Mixing different concentrations of carbon fibers and graphite powder into a Platunim Cure Silicone Rubber I was able to make a soft resistor that would change its Resistance according to bending and/or pressure applied to it.

Tested concentrations

Carbon fiber:

2.5 phr (parts per hundred rubber) – very conductive

5 phr – Very conductive

Could continue testing lower concentrations of carbon fibers

Graphite :

50 phr – silicone did not set at this concentration

25 phr- silicone did not set at this concentration

12.5 phr- resistor was not conductive enough

Could test a concentration between 25 and 12.5 phr

Photos:

Videos:

Velostat Resistor -

Ecoflex Flex/Pressure Resistor 1 -

Ecoflex Flex/Pressure Resistor 2 -

Arduino Code used:

For this project, I reverse engineered a simple traditional FSR resistive sensor in order to make it larger and textile based. The FSR sensors that are commercially made are very similar to the versions we were making in class, with a few slight variations. They essentially consist of two interlaced but separate circuit traces, a spacer and a semi conductive substrate backing- similar to the velostat we used.

I generated a pattern for my traces in illustrator and printed it out.

Using a ballpoint pen, I traced my pattern into a piece of copper tape.

I then hand cut the traces out of the tape with a metal ruler and an exacto knife (no vinyl cutter needed!) As a result, this entire project consists of materials and processes that can be performed at home without any special equipment.

I pulled up the copper from its backing using a large piece of masking tape

and then easily transfered it to a piece of light fabric which I had previously stretched across an embroidery hoop and weeded out any of the unnecessary copper with a pair of tweezers.

I cut a fabric spacer out of felt and sewed it around the copper pattern to separate the copper from the velostat.

I then sewed a square of velostat on top and proceeded to test the sensor.  I pulled the input pin low by connecting it to ground with a 10k resistor, and attached the other trace to power. With the spacer, I got a pretty good range of values from the sensor, surprisingly comparable to a commercially made one. When no pressure was generated the sensor read 0, and ranged up to 1023 in the analog read, with varying levels of pressure. The readings were also highly consistent.

I cut a basic pattern to enclose the sensor, that could be padded with additional material to make a more squeezable interface.

I stuffed the sensor inside, along with some general pillow stuffing and a piece of felt separating it from the surface of the cover. This will prevent any traces that run along the surface of the cushion from interfering with the sensor.

I rigged the sensor to a lilypad with conductive thread, and hooked up an led on the front of the cushion to act as an output mechanism. I also adjusted the code to give the sensor a bigger buffer when translating the values to the led output. (Because the cushion is stuffed, the sensor is already partially pressed.)

It works really well!

1. For this project, I wanted to build an interactive dinosaur. The dinosaur will light up when you hold his hand.

2. I first laser-cut 6 pieces of wood to make the dino’s body

3. Then I glued all the parts together

4. Then I am made the “skin” of the dino out of felt

5. I sewed the LEDs onto the felt in two intersecting parallel circuits, I used tape to make sure the circuits did not short each other.

6. “Look at my beautiful skin” – Dino

7.  Now make the arm using tape, velostat, and conductive thread. Then cover the arm with felt.

8. Then adhere the skin and the arm to the body

9. The finished dino

Dino enjoying a cup of coffee…

10. Watch Dino in action

http://vimeo.com/37609767

Lonely mitten:

My hands get super cold when biking, which is why I used to turn to this pair of mittens to keep my fingers happy. But with one mitten lost and this assignment in mind, I decided to test out an idea of embedding LEDs in the mitten to both act as an extra headlight and to call extra attention to my turn signals. My goal for the sensor was to calibrate it for various lighting modes, including fully lit LEDs with maximum pressure, blinking LEDs with less pressure, and a looping blink pattern when signaling to turn. For this purpose, I decided to make a sensor that could function as both a pressure sensor and a bend sensor (pressure for when you hold the handlebar and bend for when you signal).

Sensor:

Initial sensor testing:

MEASURING RESISTANCE:

Resting: 55-65 kΩ

Active: 1.8 kΩ

CALCULATING VOLTAGE (if internal pull-up resistor is ~35 kΩ):

Resting:

I = V/R

I = 3.6 V/(55 kΩ + 35 kΩ)

I = 0.04 mA

V= I*R

V= (0.04 mA)(35 kΩ)

V = 1.4 mV

Active:

I = V/R

I = 3.6 V/(1.8 kΩ + 35 kΩ)

I = 0.098 mA

V= I*R

V= (0.098 mA)(35 kΩ)

V = 3.4 mV

MEASURED VOLTAGE:

Resting: 0.8-1.0 mV

Active: 1.9-2.2 mV

I integrated the Lilypad into the inside of the top part of the mitten using felt and snaps:

I then sewed in the LEDs following the existing pattern on the top of the mitten:

In process:

Testing the sensor for range of values:

Writing the Arduino code:

Finally, I sewed the sensor into the palm of the mitten:

Mitten in action:

oo

Thinner blades are helpful when blowing because they have less thermal capacity and cool the glass less when used.  If you know the maximum force being applied to the glass, you can calculated the required blade thickness so they will not bend and therefore make them as small as possible.

Glass blowing is usually done with bare hands and I wanted to the gloves to interfere as little as possible. I ordered very thin liner gloves to house my pressure sensor with an unhemed liner glove on the inside and a second handed glove for the outside.

For the sensor, I chose the to use a cross between the sticky tape and fabric pressure sensors because it could be very thin with  Velostat as the sensor. The graphite infused rubber had a better resistance range, but it was too bulky to integrate into a glove.  I initially tried to make the sensor using iron-on conductive fabric, but I had trouble with the fabric melting through the Velostat as seen below.

The best sensor was single layer Velostat which had higher linearity then multilayer Velostat. I used conductive fabric instead of thread for the Velostat connection because to provides more uniform sensing. The sensor read between 2k and 150k Ohms.

The sensor was then sewn onto the interior glove using non conductive thread to hold the conductive thread down. The inside surface of glove needs to be non-conductive because it will be used with metal tools which would short the sensor.

The sensor output is displayed with four LEDs and uses PWM fading with the AnalogWrite command to give finer resolution. I used the internal 35k Ohm pull up resistor which required me to use only 25% of the voltage reading range.

Arduino Code

The final glove worked well for showing variation in bending or squeezing, but the resistance goes too low from squeezing alone for it to work well with glass blowing. I would need to change the sensor to not be effected by bending to make it more effective.

Calculations:

R_min = 2kOhms

R_max = 150 kOhms

R_pullup = 35 kOhms

V_max = 5V (doesn’t actually matter since LED control is from relative voltage readings, not absolute)

V_out = V_max * R / (R + R_pullup)

V_outmax = 4.05 V

V_outmin = 0.27 V

Once the sensor was installed in the glove, the pressure from just being in the glove lowered the maximum resistance to about 30 kOhms

V_outmax = 2.30 V

I used these ranges to calibrate the values for my LED turn-on.

I experimented a lot with several different projects before settling on this one and learned quite a bit during the process. One thing I learned was the need for a good plan for the circuitry so that it would be organized and not messy when making the paths to the LilyPad.

Here is my plan for the circuitry for my puppet (while laid flat):

After I created the bend sensor, I made sure to measure its resting resistance using a multimeter to make sure that the resistance would decrease when I bent the sensor.  At first, my measurements did not return a very high resting resistance so I added an additional piece of velostat so that the sensor would be less sensitive and return a higher range of resistances when bent.

As I sewed the circuits on the felt, I made sure to measure for continuity as I went along to make sure everything was connected before I got too far. I also wrote a few test programs in Arduino to test out the connections to LED lights.

I sewed all the circuits in place and this is what it looked like before I assembled the puppet.

I then assembled the puppet and added the hair with the stroke sensor.  Since this sensor would be digital I had to make sure that it was assigned digital pins on the LilyPad. I also had to create a “ground pin” in my program since I could not reach the Negative pin without crossing paths with another circuit.

I finally then programmed the LED lights in Arduino so that when the mouth is wide open, the LEDs light up in a “chasing” pattern. When the mouth is half way open, the lights slow down, and when it is closed, the lights turn off.

When you stroke the hair on the puppet, the LED on its head lights up when the conductive threads touch each other.

Here is my finished product and accompanying video:

Measurements: (Note: my calculated measurements did not seem to line up exactly but this could be because the resistance of the resting position of the bend sensor was taken when it was outside of the puppet, but voltage was measured while inside of the puppet. The curvature of the mouth most likely made it so that the resting resistance was slightly less when inside the puppet, thus throwing off my predictions).

Measured:

Calculated:

Measured:

The materials I had access to were velostat, felt, conductive material, conductive thread, 5 LEDs, snaps, the sewing machine, and the Lilypad Arduino. The main idea I had is that I wanted the glove I am making to respond to touch, which can be achieved by making a resistive sensor that decreases its resistance if pressure is applied to it. I experimented with using velostat to make a resistive sensor. I searched online for previous work on these kind of resistive sensors and came across one on Instructables by Plusea. I read through the method and used it as sort of a guide in creating my own.

step 1: Cut four pieces of felt into small, button-like shapes. I cut four pieces even though two will achieve the goal because I want the button to have a rather thick texture so it feels nice.

step 2: Cut four pieces of velostat into circles. I know that I may not use all four, because if I put too much velostat in the sensor, that means it will have a higher resistance. The internal pull up resistor in the Lilypad is ~35k and I need the sensor to have resistance on the same magnitude as the internal resistor in its inactivated state for the pressure sensor to work nicely.

step 3: Next I double threaded the needle to sew a simple pattern onto one of the felt pieces. Notice I sewed a piece of conductive fabric to the end of the felt pieces. This is to make it so that I can connect other pieces of the circuit to the sensor easily. I double threaded the needle because it allows more current to travel through, which gave me a small control over the resistance of the thread. It also allows me to make the sensor more responsive to pressure. I did the same for the other side of the felt piece.

step 4:  The two felt pieces come together, sandwiching the conductive thread in between. I placed an extra felt piece on either side of the sensor to 1) hid the conductive thread and 2) create a nicer, thicker texture for the sensor.

step 5: Now is the time to play around with how much velostat to put into the sensor. As mentioned earlier, I wanted to create a sensor which has a resistance on the same magnitude as the internal pull-up resistor in deactivated state. As for my sensor, I still wasn’t sure how many pieces to put in at this point, so I just moved onto the next part for now.

step 6: Making the glove is very tricky. As I’ve never sewn before, I viewed this as a fun challenge. I traced a pattern around my hand and cut out the shape on felt. The first three iterations did not work well because, as a common mistake, I cut the pieces too small and neglected to account for the third dimension of my hand. However, the fourth iteration was successful and I sewed it up with the sewing machine.

step 7: In order to attach and detach the Arduino to my glove, I soldered buttons to the Lilypad and pressed buttons into a piece of felt so that I can button the Arduino on to the glove.

step 8: It takes a little effort in mapping out the exact route of the circuit on the glove so that 1) the wires don’t cross, 2) the glove looks aesthetically pleasing, and 3) the circuit functions correctly. This is the design I came up with for the back of the glove. The palm of the glove is simpler than the front: the A5 pin simply go to one side of the sensor and ground goes to the other side of the sensor. All the LEDs are connect to ground on the palm of the glove in a similar “whirlwind” pattern of the front of the glove. All the stitches are done with conductive thread, double threaded to decrease their resistance.

[palm  +  back of the glove]

The physical assembly is now almost complete with the exception of how much velostat to put in the sensor. I used the serial monitor on the Arduino to aid me in calibrating the sensor. After writing some simple code and turning on the serial monitor, I discovered that putting three pieces of velostat in between the felt allows me the best range in voltage drop over the sensor as a pressure sensor.

Resistance | Calculated Voltage across sensor |Measured Voltage Drop across sensor

400kΩ       |                       3.4V                                    |                          3.4V                                      |                  inactive

1kΩ             |                     0.12V                                   |                       0.2 V                                        |                active

Now that the physical assembly of the glove is finished, the software portion of the project begins. I wrote a couple of behaviors for the glove to make it interesting. These behaviors can be seen in this video.

behavior 1:  When the glove is not squeezed, the LEDs on the thumb, middle and pinky fingers light up. When it is squeezed, the LEDs on the forefinger and the ring finger lights up instead.

behavior 2: This is a visualization of how hard the glove is being squeezed. The LEDs turn off in a linear relationship with how hard you are squeezing or pressing the glove.

behavior 3: This pattern can be used in a game of roulette or a game of “red light/green light.” (Except the title will be modified to “light on/light off” of course.)