I talked a little bit about the technology going into Holding-Hands in my earlier post "Materials & Resources." I've since made some adjustments to the project, and expanded upon the tech components which I will detail here.
A couple weeks ago I ordered the Lilypad arduino, 2 5V heating pads, 2 servo motors, and conductive thread. Though I'm new to the Lilypad, I chose it over the arduino Uno because it can be sewn directly into the project and is much less bulky. The coding is the same, but the board can only support 2-5 Volts (so using the board to power all the components would fry it). Therefore I've added a few more components to the list to fix the power issue (these will be coming in the mail soon).
Here's what I have so far:
A. 5V Heating Pads: I ordered two of these from SparkFun here: https://www.sparkfun.com/products/11289
I also found a helpful tutorial for installing the heating pads which includes the circuit and code (very similar to the plans I'll soon be releasing for this project) https://learn.sparkfun.com/tutorials/heating-pad-hand-warmer-blanket
The heating pads will be hooked up to their own power sources independent of the arduino. They will still communicate with the arduino through a MOSFET
MOSFET: A MOSFET allows you to control high powered devices with microcontrolers (low powered controllers like the Lilypad). The MOSFET acts as a programable power switch, with three legs: one to the arduino pin, one to the heating pad, and one to the power source. I ordered two of these from SparkFun https://www.sparkfun.com/products/10213
Here's a helpful introduction to the MOSFET from bildr: http://bildr.org/2012/03/rfp30n06le-arduino/
B. Lilypad Arduino: This component will serve as our controller: a mediator between the code and our components (input and output). The Lillypad comes in many designs (some with less pins, some with direct USB plug in) I ordered the 328 Main Board, and realized upon arrival that I still needed a battery hook up (which is another pad with its own special battery) and an FTDI cable (to plug the arduino into the computer for uploading the code). I just order the cable here: https://www.sparkfun.com/products/9717 But there are other options (buying a LilyPad FTDI Basic Breakout board & cable Or buy the LilyPad Arduino USB version with a micro-USB cable)
C. Lithium Polymer Quick Charger: A battery charger for the 3.7V battery (from SparkFun)
D. LilyPad LiPower & LiPo battery: These components supply power to the LilyPad https://www.sparkfun.com/products/11260
E. Servo Motor: Two motors (one in each hand) will turn and tighten threads connected to the digits of the hand, causing them to close together. The servo motor I ordered comes with a variety of wing pieces (in the plastic bag next to the servo).
Here are some servo refereces I'm using for the project: Explaination-https://www.youtube.com/watch?
Specs-feature=player_embedded&v=vUOBiCWwJjo#t=349shttp://dlnmh9ip6v2uc.cloudfront.net/datasheets/Robotics/Hitec-HS-425BB-Servo-Specsheet.pdf
Coding-http://arduino.cc/en/reference/servo
F. Button: Lastly, you're going to need a button to turn the Holding-Hands on and off. There are many kinds of buttons/switches but each operate on the same basic idea: push the button, close the circuit, supply power = ON. The button I have pictured here is a temporary solution. Ideally I would make my project touch activated (so that the hands would be on whenever the scarf was being worn). I'm still working on this, so for now we'll use a button - I've ordered this button (a flat sewable on-off switch) https://www.sparkfun.com/products/9350
In addition to these components you'll need Conductive Thread, Connective Wire, and batteries (LiPo or Coin Cell) These will connect the components and power them.