FROM: EECE 380 Lab Group L2B5

TO: Dr. Michelson and Lab TAs

DATE: February 24, 2014

SUBJECT: Fourth Week Summary

During the past two weeks our team has built a circuit for the sensors and tested a model pipe we built for measuring water level. We also further modified DemoAppFFS to send time along with data.

The following part of the memo documents the functions of the circuit. For measuring water level, it is done using the concept of parallel plate capacitor. Two sheet of aluminum foil is wrapped around the pipe acting as two plates of a capacitor. The pipe along with aluminum foil will have different capacitance depending on the amount of water inside the pipe. Two wire is connected from the two sheet of aluminum foil to a 555 timer circuit. The circuit outputs various frequencies depending on the capacitance of the pipe. Then the DC frequency is inputted into LM331 chip which convert DC frequency to a corresponding DC voltage.

Temperature sensing is done using the temperature sensitive diode LM335. There will be different voltage drop across the diode depending on the temperature of the surrounding. This dc voltage can be measured and later be converted into temperature readout.

The output DC voltage for both circuit also passes through amplifiers to change its voltage range in order to fit the 0-3.5v range of Orbcomm modem’s ADC.

In the next week we will begin soldering the circuit and complete any final calibrations for both sensors. We will also begin to look at the actuator of the modem and build any circuits needed. The actuator will graph out the date with time from the emails we set from DemoAppFFS.

Sincerely,

EECE 380 L2B5