The idea behind the system.

Дата на публикуване: Sep 22, 2010 10:18:51 AM

This type of system will be used to keep the temperature in the vivarium as close as possible to the temperature of the real world tropical area.

To do this I decided to use termo - electric cooler.This is a PN element that when there is a current across it one side of the element gets hot, another one get cold.

I decided to use this one, because there is no moving parts, it's cheep and silent.

The disadvantage of using this TECs is that there are not so effective as compressor stage coolers but for small project like this I think it ok.

I choose a city named Libreville in Gabon for a temperature example.The city is located in the west coast of Africa, few degrees north of equator.I did this because there is a big airport in Libreville and I was able to download the meteo data for this airport for few days.So I was able to calculate the average temperature in each half hour.

I used this temperature to create next graphics :

On the Y axis is the temperature in mC, on the X axis is the time i 1/2 hour.

Next I used the trendline option in Excel and I make a equation from this graphics.

On the top left right corner is the equation of the changing of the temperature.I simplify it a little bit, so it will take only 300 instructions to be calculated.

Before I reach the process of calculating the current temperature I use another variable which I named simply "D".This is necessary because the controller will have an option to select sunrise and sunset.So "D" will be 1 at sunrise and will be increase at each 30min with 1.

So the final formula for calculating the current temperature using the sunrise time as a variable is :

temp = ((D^3)-(99*D^2)+2500*D+44942)/2

I used a division by 2 because it's simple rotation to right in the ASM and the numbers are only integers.

So at the end I will try to make temperature swinging between 32 and 24 C.