Sunday, November 6, 2011

Project 4 -- Major Project: initial survey..

Since this project involves THERMISTORS, i've gone to my other tech blog to see what i've done there.

And this entry has a handy data-table ^..^ .

The idea is to make a strip of about 4 or 5 thermistors to hang inside the door of my fridge; i want to see how much colder it is at the bottom compared to the top.

I know it is colder at the bottom, because meat keeps longer there, & sometimes starts to freeze, whereas it never does  that nearer the top.

I need some of that ribbon cable to 'insert' the thermistors into, & also to transmit data to the analog pins on my Arduino.  i also have a USB power supply, so i could actually do some data-logging over an extended period & save the data to EEPROM for later retrieval & display (& just by chance i've found a LED-strip with about 10 LEDs on it that i'd forgotten i had!).

I'd like to add TWI to a 24LCxx if i can, as that would allow more data to be stored.

A photo-cell (these entries) could tell me when the fridge door was opened.

Another little wrinkle would be to average all the thermistor readings at any one time, &  switch on a motor, say, if the average temperature rises above a preset value.

First things first, however: i need to set up the thermistor strip, write the basic software, & get that part working;  i can add bells & whistles later.

3 comments:

  1. got a bit mixed up with Polling Routines & the need to suspend timer routines while polling.

    TWI doesn't require this so i won't have to start/stop TWI while setting a delay between thermistor readings..

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  2. however, i don't want to be 'interrupt'ed while actually logging data (stopping in the middle of a TWI cycle is not good for reliablility) so we say:
    noInterupts()
    .
    ..some datalogging software
    .
    interrupts()

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