====== Electrical ======
==== Calculator ====
http://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.htm
==== Impedance ====

Impedance is equal to voltage divided by current. This means that a 4-ohm speaker draws more current than a 6-ohm speaker; more current gives it more power and usually enables it to play loudly more easily. 
\\ http://www.prestonelectronics.com/audio/Impedance.htm
\\ It should be apparent by now that there is a relationship between pressure (voltage), flow (current) and restriction (impedance).  

Example:
  * Impedience (ohms?) = V/Current
  * Current(Amps) = Voltage/Impedeince(ohms)
  * On Little laptop speaker
  * With volt meterd measured .004 x 2000 = 8
  * BUT the device says 4 ohoms
Arduino puts out 5 volts when analog pins (8-13) are set to HIGH
  * 4ohms = 5V/Xamps
  * or
  * 5V/4ohms = Xamps
  * 
  * 4/1 = 5/x
  * 4/5=x
  * x=.8
  * I need .8 amps of current


====== LEDs ======

A very good calculator and aproximation of typical LED's if you do not have spec sheets:
\\ http://led.linear1.org/1led.wiz
\\ In the example:
  * 5volts
  * 3.3 forward voltage @20mA (recamended for 3-5mm LED's of a white color
  * =APROXIMATELY a 100 ohm resistor at 1/8 Watts

LED calculation
  * http://www.ehow.com/how_5865769_choose-resistors-12-volt-leds.html
  * subtract forward voltage (assuming 3.3, as above)
  * From Power supply 5
  * =2.7
  * Divide the result by current raiting (assuming 20map, and dont forget that 
  * 20mA is equal to .02 Amps
  * 2.7/0.02=
  * 135

Other, basic system:
  * http://www.ehow.com/how_7810698_resistor-size-needed-electrical-circuit.html
  * 5v/.02A=
  * 250
  * or if we are to asume voltage of device
  * 3.3/.02=
  * 165