Temperaturabhängige Lüftersteuerung

Der Gate Pin des FETs, der den Lüfter regelt wird an PD7 angeschlossen. Mit dem Skript lassen sich nun die Umdrehungen abhängig von der Temperatur, die am Onewire-Sensor gelesen wird per Hardware PWM regeln.

Das Skript regelt zwischen 28.2° und 60° (darunter ist der Lüfter aus weil hier meist die Raumtemperatur liegt und es dadurch keinen Kühleffekt mehr gibt, darüber läuft der Lüfter auf 100%)

dnl ################################################################################
dnl #                                                                              #
dnl #  Copyright (c) 2011 by Maximilian Güntner <maximilian.guentner@gmail.com>    #
dnl #                                                                              #
dnl # This program is free software; you can redistribute it and/or modify it      #
dnl # under the terms of the GNU General Public License (either version 2 or       #
dnl # version 3) as published by the Free Software Foundation.                     #
dnl # This program is distributed in the hope that it will be useful,              #
dnl # but WITHOUT ANY WARRANTY; without even the implied warranty of               #
dnl # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the                #
dnl # GNU General Public License for more details.                                 #
dnl #                                                                              #
dnl # You should have received a copy of the GNU General Public License            #
dnl # along with this program; if not, write to the Free Software                  #
dnl # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.                    #
dnl #                                                                              #
dnl # For more information on the GPL, please go to:                               #
dnl # http://www.gnu.org/copyleft/gpl.html                                         #
dnl #                                                                              #
dnl ################################################################################
CONTROL_START
THREAD(mainloop)
        ON ONCE (1) DO
                int16_t temperature = 0x7FFF;
                for(uint8_t i=0;i<10;i++)
                {
                        temperature = (ONEWIRE_GET(28a419e002000017));
                        if(temperature != 0x7FFF)
                                break;
                }
                dnl 0.425: x/600*255 (60° will result in 255 => maximum fan speed)
                double newvalue=0.425*temperature;
                dnl Set fan to maximum
                if (newvalue > 255)
                        OCR2A = 0;
                dnl Disable the fan, cooling makes no sense
                else if(newvalue < 120)
                        OCR2A = 255;
                dnl Set the fan to the dynamic value
                else
                        OCR2A = 255-(uint8_t) newvalue;
        END
THREAD_END(mainloop)

ON STARTUP DO
        dnl PD7 has to be output
        DDRD |= 0b10000000;
        dnl FastPWM
        TCCR2A = (1 << COM2A1) | (1 << COM2A0) | (1 << WGM21) | (1 << WGM20);
        dnl Prescaler: 1024
        TCCR2B = (1 << CS22) | (1 << CS21) | (1 << CS20);
        dnl Maximum Speed
        OCR2A = 0;
        THREAD_START(mainloop)
END
CONTROL_END