/ /INTRODUCTION

The Lilypad Arduino is a microcontroller designed by Leah Buechley for use with fabric. It can be sewn into a shirt, handbag, etc., and used to control LEDs, accelerometers, and other outputs and sensors. The Lilypad is a type of Arduino:

The pins labeled a0 to a5 are analog in. The other pins (with the exception of +V, -, tx, and rx) are digital I/O pins. The Lilypad contains an Atmega168V, so, as per this page, pins 3, 5, 6, 9, 10, and 11 can do analog out (PWM).

Sewing the LilyPad Arduino

The hole on each tab of the LilyPad is large enough for a sewing needle to pass through. You can make both electrical and physical connections with stitching in conductive thread. Sew through the holes several times to insure good contact. Here's a picture showing a sewn LilyPad:

Connecting

Connecting to the computer using an encapsulated FTDI cable. This is what your connection should look like. The green wire goes on the right and the black wire goes on the left:

When working with the lilypad, making coasters will save you from being frustrated with slipping alligator clips:

1. Trace the outline of the LilyPad on your foam or other material.
   
   
   

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2. Cut out your coaster.
   
   
   

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3. Clip your LilyPad back to your attachment setup. The alligator clips should now have a nice sturdy grip on the LilyPad, with good electrical contact and no slipping.
   
   
   

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4. Cut out coasters for LilyPad sensors and actuators. If you got sensors and actuators to play with, cut coasters for them too. This will allow you to easily use alligator clips to prototype designs.br />
   

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Keep your power supply and LilyPad main board as close to each other as possible in your constructions. If they are too far apart, you are likely to have problems with your LilyPad resetting or just not working at all. Conductive thread has non-trivial resistance. (The 4-ply silver-coated thread from SparkFun that comes with the LilyPad starter kit has about 14 ohms/foot.) Depending on what modules you're using in your construction, your LilyPad can draw up to 50 milliamps (mA) of current, or .05 Amps. Ohm's law says that the voltage drop (the amount of voltage that you lose) across a conductive material is equal to the resistance of the conductive material times the amount of current that is flowing through it.

For example, if your LilyPad is a foot away from the power supply, the total resistance of the contuctive material that attaches your LilyPad to your power supply is about 28 ohms. (14 Ohms in the conductive thread that leads from the negative terminal of the power supply to the negative petal on the LilyPad and 14 Ohms in the conductive thread that ties the positive terminals together). This means we can expect a drop of 1.4 Volts (28 Ohms * .05 Amps.) This means that while 5 Volts is coming out of the power supply, the LilyPad will only be getting 3.6 Volts (5 Volts - 1.4 Volts). Once the voltage at the LilyPad drops below about 3.3 Volts, it will reset. In other words, you don't want the voltage at your LilPad to ever drop below about 3.5 Volts.

If you are experiencing this kind of problem, you want to either decrease the resistance of your traces or decrease the amount of current your design is drawing. To decrease the resistance of your traces, you can stitch over existing traces with another layer of conductive thread (or, even a fine wire if you're desperate). To decrease the amount of current your design is drawing, try not to run several things at once. For example avoid powering a tri-color LED and vibrator motor at the same time if you can.

Also, pay special attention to the stitching at the power supply and at the + and - tabs on the LilyPad. The power supply connection is the most important one that you'll sew in your project. You want to make sure you get excellent contact between the tabs on the power supply and your conductive thread. You also want to do everything you can to keep the power supply from moving around on the fabric. I recommend gluing the power supply in place and then sewing it. If you're sewing it to a thin, delicate, or stretchy fabric, you should glue or sew something underneath the power supply to help prevent it from pulling on the fabric and bouncing around as you move.

/ /Sensing Switches

1. A switch is basically 2 pieces of conductive material that are sometimes pressed together and sometimes kept apart. The switch is CLOSED (pressed or triggered) when the conductors are pressed together and OPEN when the conductors are separated.
   
   Attach a black alligator clip to the - tab on the LilyPad and an alligator clip of a different color (preferably not red) to tab 2 on the LilyPad. Now, when you touch the two alligator clips together you are closing or pressing the switch. Note that when you touch the clips together, the switchPin (flower petal 2) will be attached to ground or - via the alligator clips. GND in Arduino code is referred to as LOW and power or +5V as HIGH.
   

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2. Attach the LilyPad to your computer and start the Arduino software
   

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3. Copy this sample code into an Arduino window

   // LED is connected to digital pin 13
   #define  ledPin  13
   
   // switch connected to digital pin 2
   #define switchPin 2  
   
   // a variable to keep track of when switch is pressed
   int switchValue;
   
   
   void setup(){
   // sets the ledPin to be an output
   
       pinMode(ledPin, OUTPUT);
   // sets the switchPin to be an input
       pinMode(switchPin, INPUT);
    // sets the default (unpressed) state of switchPin to HIGH
      digitalWrite(switchPin, HIGH);
   }
   
   void loop(){
   
    // check to see if the switch is pressed
       switchValue = digitalRead(switchPin);
        if (switchValue == LOW) {
   // if the switch is pressed then,
   // turn the LED on         
        digitalWrite(ledPin, HIGH);
   
        }else {
   // otherwise,turn the LED off
             digitalWrite(ledPin, LOW);
        }
   
   }
   

   
   

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4. Load the code onto the LilyPad. Do this by hitting the upload button in the Arduino window (that's the right pointing arrow at the top of the Arduino window) and then quickly pressing the reset switch on the LilyPad.
   

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5. See what happens when you close the switch!
   
   The LED should come on. If it doesn't, check to make sure your alligator clip connections are good.
   

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6. Play with modifying the code to get different behavior
   • Can you get the LED to turn on when the switch is open and off when the switch is closed? (Basically swapping the behavior of the sample code.)
     

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   • Can you get the LED to blink quickly while the switch is closed and turn off when the switch is open?
     

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   • Something a little more challenging... can you get the LED to toggle on and off with each press of the switch? That is, the first time you press the switch, the LED turns on, the second time you press the switch it turns off, and so on?
   
   

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7. Build your own switch
   
   As you can see from the alligator clip example, it's easy to build a switch. Play with different materials to make your own switches. Some of the interesting conductive materials that you can use to make switches are conductive velcro, conductive fabric, conductive thread, aluminum foil, metal springs and metal beads. Use your imagination and whatever is lying around the house!

/ / Sample Project

1. Plan the aesthetic and electrical layout of your piece.
   
   Decide where each component is going to go and figure out how you will sew them together with as few thread crossings as possible. Make a sketch of your design that you can refer to as you work:
   
   
   Stitching for power (+) is shown in red, ground (-) in black, LEDs in green, and switch inputs in purple.
   
   
   Close-up of the left sleeve
   
   
   
   
   

   important note about the power supply

   As you design, plan to keep your power supply and LilyPad main board close to each other. If they are too far apart, you are likely to have problems with your LilyPad resetting or just not working at all.
   
   Why? Conductive thread has non-trivial resistance. (The 4-ply silver-coated thread from SparkFun that comes with the LilyPad starter kit has about 14 ohms/foot.) Depending on what modules you're using in your construction, your LilyPad can draw up to 50 milliamps (mA) of current, or .05 Amps. Ohm's law says that the voltage drop across a conductive material--the amount of voltage that you lose as electricity moves through the material--is equal to the resistance of the conductive material times the amount of current that is flowing through it.
   
   For example, if your LilyPad is a foot away from the power supply, the total resistance of the conductive material that attaches your LilyPad to your power supply is about 28 ohms. (14 Ohms in the conductive thread that leads from the negative terminal of the power supply to the negative petal on the LilyPad and 14 Ohms in the conductive thread that ties the positive terminals together). This means you can expect a drop of 1.4 Volts (28 Ohms * .05 Amps.) This means that while 5 Volts is coming out of the power supply, the LilyPad will only be getting 3.6 Volts (5 Volts - 1.4 Volts). Once the voltage at the LilyPad drops below about 3.3 Volts, it will reset. The resistance of the traces from + on the power supply to + on the LilyPad and - on the power supply to - on the LilyPad should be at most 10 Ohms. Plan the distance accordingly.
   
   

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2. Transfer the sketch to your garment. Use chalk or some other non-permanent marker. If you want, use a ruler to make sure everything is straight and symmetrical.
   
   

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3. Use double sided tape to temporarily attach LilyPad pieces to your garment. This will give you a good sense of what your final piece will look like. It will also keep everything in place and, as long as the tape sticks, make your sewing easier.
   
   

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4. Stabilize your battery on the fabric. Generally, you want to do everything you can to keep the power supply from moving around on the fabric. Glue or sew the battery down before starting on the rest of the project. You may also want to glue or sew something underneath the power supply to help prevent it from pulling on the fabric and bouncing around as you move.
   
   If you are working on a thin or stretch piece of fabric--first of all, reconsider this choice! It's much easier to work on a heavy piece of non-stretchy fabric. If you are determined to forge ahead with a delicate fabric, choose the location for your power supply wisely. It's the heaviest electronic module, so put it somewhere where it will not distort the fabric too badly. definitely glue or sew something underneath the power supply.
   
   

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5. Sew the + petal of the power supply down to your garment. Cut a 3-4 foot length of conductive thread. Thread your needle, pulling enough of the thread through the needle that it will not fall out easily. Tie a knot at the end of the longer length of thread. Do not cut the thread too close to the knot or it will quickly unravel.
   
   Coming from the back of the fabric to the front, poke the needle into the fabric right next to the + petal on the power supply and then, from the front of the fabric, pull it through. The knot at the end of the thread will keep the thread from pulling out of the fabric. Now make a stitch going into the hole in the hole in the + petal on the power supply. Do this several more times, looping around from the back of the fabric to the front, going through the + petal each time.
   
   

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6. Pay special attention to this stitching. It is the most important connection that you'll sew in your project. You want to make sure you get excellent contact between the petals on the power supply and your conductive thread. Go through the hole several times (at least 5) with your stitching. Keep sewing until you can't get your needle through anymore. Do not cut your thread, just proceed to the next step.
   
   

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7. Sew from the battery to the LilyPad. Once you've sewn the + petal of the battery down, make small neat stitches to the + petal of your LilyPad. (I used a jacket with a fleece lining and stitched only through the inner fleece lining so that no stitches were visible on the outside of the jacket.)
   
   
   

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8. Sew the + petal of your LilyPad down, finishing the connection. When you reach the LilyPad, sew the + petal down to the fabric with the conductive thread. Just like you were with the battery petal, you want to be extra careful to get a robust connection here. This stitching is making the electrical connection between your power supply and LilyPad
   
   
   

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9. In the same way, sew the - petal of the power supply to the - petal of the LilyPad.