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Project Overview

The Voice Messager project implements a device that integrates a digital answering machine capability to store several voice messages with the size and portability of a voice recorder.  In order to do this, the device converts the analog input signals into digital representations.  The signals are converted using an A/D converter and then stored into a SDRAM chip.  We are using the SDRAM technology because of its low power consumption.  A micro-controller controls the storage of the signals in the SDRAM, as well as the time the message was input, and the length of the message. 

The user then selects through the different signals and chooses which to hear.  The micro-controller also controls the user input functions to determine where to retrieve the message from the SDRAM chip.  A D/A converter is to convert the digitally stored messages into an analog form in order for proper speaker or headphone output.

Three concerns that were expressed to us by our client are voice quality, battery life, and adequate message duration.  The first and most important is the output voice quality.  The output quality shall match or come as close as possible to the input signal.  To achieve this, we must obtain the highest quality A/D and D/A converters available.  The second concern is power consumption.  This issue pertains to the battery life of the device.  The battery shall be as small and last as long as possible while maintaining signal integrity and proper functionality.  Our goal in this category is to have 3AA batteries last 2 weeks.   The final issue is message duration.  We must create this device with enough RAM to enable the user to store a sufficient number of messages along with a reasonable amount of time for each of the messages.  Our goal here is to be able to record 12-15 messages with a duration of 1 minute each.

In order to make this device unique and marketable, the team decided on additional design concerns.  Of these self-assigned tasks, the main point of focus is to make this device environmentally resistant.  This includes shock resistance, water resistance, and the ability to withstand a reasonable temperature range.  Another feature the team decided to implement was a backlight feature for the LCD display for night time viewing.