Memorandum 

Date:               March 30, 2014

To:                  Professor David G. Michelson

From:              EECE 380’s L2D4 Group

Subject:          Update on Orbcomm Design Project

The focus of this week was the completion of the electro mechanical sensor, power source, a multiplexer and various aspects within the coding.

Software

The week we focused on saving the sensor data in the event of satellite being out of range. This was achieved by writing the data line by line into a text file inside the modem. In order to do this was used functions such as FFS_WRITE and used FFS_READ to read that file into an array in order to send those saved messages in the event the satellite is back in range. We have 5 analog signals coming in and there are only 2 analog ports in the modem, thus we needed a multiplexer. The next challenge was to use the digital ports of the modem and configure them as outputs in order to control the multiplexer. This was achieved with various DIO functions.

Hardware

With the assembly of the solar panel we realized a DC buck converter was necessary. Input is 9V and 15mA from the solar cells and the output from the converter is 4.5V 25mA, and it conserves 90% of the power. This is being used to power all the sensors. We also made the wind speed sensor using a brush less DC motor attached to an apparatus on the top which catches the wind and thus spins the motor generating voltage. After testing the voltage we noticed that the output of the motor is too low for the modem to accurately display. Thus we used a simple non-inverting amplifier that amplifies by 100 to give the modem a reading it can actually use.

The goals of this week were achieved. The goals for next week are to assemble the project together and debug it. Also calibrate the sensors for accurate measurements.