Maximum and Minimum thermometer

Hi to Everyone this is my very first question in the forum. I hope that I am in the right area to put my question.

I wonder if it's possible to construct a maximum and minimum thermometer using the Raspberry Pi, if so what is required as regards hard ware etc and skill level of course?

My thanks in advance.

0 iagorubio over 11 years ago

If you mean a thermostat, yes it's possible.

I use usually the DS1620 Maxim digital thermometer as it have thermostat but it's a bit complex.

The 1-Wire DS18B20 is much easier and there is a lot of work done to make it work with raspberry.

Look here for more information
Raspberry Pi 1- Wire Digital Thermometer Sensor | Raspberry Pi Spy
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0 Former Member over 11 years ago in reply to iagorubio

Many thanks for your prompt reply.
I had in mind something that would display the maximum and minimum, with the sensor outside and the Raspberry Pi on the window sill.
Thanks once again
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0 johnbeetem over 11 years ago

Here's another project using the DS18B20 1-Wire temperature sensor with RasPi: https://learn.adafruit.com/large-pi-based-thermometer-and-clock/
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0 Problemchild over 11 years ago in reply to johnbeetem

Yep follow John's idea with the Dallas 1 wire sensor this is already well supported so you will find drivers already about making your life much easier.
You can then read the values from the sensor using say a Python program or what ever language you are experienced in
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0 Robert Peter Oakes over 11 years ago

and if you want to have a small LCD display to keep the power lower then this would be relatively easy to add

http://canada.newark.com/adafruit-industries/1115/blue-white-16x2-lcd-keypad-kit/dp/52W9087
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0 Former Member over 11 years ago

I'm using the 18B20 with the Pi (with Raspbian) at the moment: very simple to interface and to use. This bit of PHP works to get min/max readings (the 28-000.... file corresponds to the 1-bit identifier of the temperature sensor):

<?php

//Init sensors if necessary
$dir=scandir("/sys/bus");
if(!array_search("w1",$dir)){ // devices not there yet
    exec("modprobe w1-gpio");
    exec("modprobe w1-therm");
}

$device="/sys/bus/w1/devices/28-000005a1fbf8/w1_slave";
$highest=-1000;
$lowest=1000;

while(true){

    $lines=explode("\n",file_get_contents($device));
    if( preg_match_all("/YES/",$lines[0],$matches) ){   // CRC is good
        if( preg_match_all("/t=(\d+)/",$lines[1],$matches) ){
            $pf = round( $matches[1][0] / 100 )/10;
            $highest = $pf>$highest? $pf:$highest;
            $lowest = $pf<$lowest? $pf:$lowest;

            printf("Highest = $highest, Lowest = $lowest\n");
        }
    }
    sleep(1); //wait until next reading

}

?>
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0 Former Member over 11 years ago in reply to Former Member

Many, many thanks for all your replies quite a lot to take in I'll read up on all of the links. Thanks once again
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