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== Kill-A-Watt ==
In this demonstration we will be using a Kill-A-Watt. We will be receiving current and voltage data from the Kill-A-Watt’s Op-Amp
and is wirelessly transmitted using the Zigbee module. You can use other power meters but you cannot know if will work unless you open it and examine it. Also the Kill-A-Watt's size is excellent to house the ZigBee unit. The ZigBee RF chip has an embedded micro controller which allows you to do some simple operations without having to program a micro controller. The software provided by Digi X-CTU allows you to change variables such as sleep timer easily. Unfortunately, it also limits you too, without an a third party micro controller you can't insert nonvolatile memory. As a result if there was power outage a portion of your data will be lost.
[[Image:xbeewatt.png|thumb|Figure 1: Schematic of the Kill-A-Watt with Zigbee transmitter [http://www.ladyada.net/make/tweetawatt/solder.html]]]
The XBee unit receives it's power from the Kill-A-Watt. Unfortunately the current received is lower than required to run the Xbee as a result a large capacitor is used to account for the current needed. The C1 and C2 is to provide a constant voltage to the 3.3V regulator and C3 capacitor on the reset pin of the Xbee will help delay the transmitter to allow the other capacitors to charge up again. The voltage divisor is used to decrease the sensors inputs received from the Kill-A-Watt at 5V to 3.3V. The last resistor is used to power the LED.
In this demonstration we did not create our own circuit board but instead used one that was meant for the receiver. Creating your own transmitter circuit board will greatly increase the speed and simplicity of putting this together.