Environmental Monitoring with the Tessel 2
rwaldron 
Materials
To build the monitoring device, you'll need the following parts:
Parts to Source Elsewhere
- 47uF capacitor
- Air Conditioner Extension Cord, 3' (Amazon)
Meet the Supporting Hardware
Non-Invasive Current Sensor
The non-invasive current sensor has a "jaw" that clamps around a wire. It can read the amount of current flowing through the wire without the wire itself having to be modified (ergo, non-invasive). By plugging the air conditioner into the extension cord and then using the current sensor to detect how much current is going through the extension cord, we'll be able to tell when the AC is running.
The current sensor's output is a current much lower, but linearly related to, the current it's sensing.
TRRS Breakout
The non-invasive current sensor has a connector that looks like an audio jack on one end. It is a TRS (Tip-Ring-Sleeve) connector, shown on the left side of the diagram below. You may also have seen TRRS connectors (Tip-Ring-Ring-Sleeve, right side of diagram), which are commonly used for handsfree headsets. The TRRS breakout makes each of the pieces of a TRRS connector (the tip, each of the two rings and the sleeve) accessible. The TRRS breakout will allow us to easily connect to the tip and the sleeve of the current sensor's connector so we can read its values.
