Project 3 -- Minor Project: Design

My MINOR PROJECT has the following hardware design features:

** 3 thermistors on a wiring loom able to be set up inside my fridge.

** 1 photocell on the same wiring loom.

** A Duemilanove Arduino board, 
     to poll the 3 temperatures at around 1 minute intervals,
     with an interrupt feature involving the photocell
     (for when the door is opened - & closed again,
     & the software to save to & retrieve the data from the on-board EEPROM.


The whole project can be independently powered through the USB port - i have a USB power source, but a bit of tweaking may enable power to be supplied by a 9v battery (not sure about this).
    
The software design involves the following:

** Regular polling of the 3 thermistors connected to Analog pins A0, A1, A2.
     Their readings are saved to EEPROM

** An interrupt feature triggered by the photocell connected to Analog pin A3.
     The interrupt is attached to Digital pin 2, 
triggered by the photocell reading  rising above a pre-determined 'darkness' threshold.  
     A LED will be lit & the fact recorded on EEPROM in binary form (1 = open).


** A Serial Monitor connection enabling retrieval of the recorded data on a signal from the serial connection (via SM).


** A software delay enabling the project to be set up & connected to its power source - nothing will happen for about 5 minutes - then the program starts recording data.


** The software delay can be over-ridden by a signal from the SM, when the project is connected to a PC; data retrieval can then begin.


** Data retrieved from the EEPROM is written to the SM, appropriately formatted.
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