Control DC fan motors with PWM along with a minimum PWM duty before turning on.

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Show/hide line numbers DcFan.cpp Source File

DcFan.cpp

00001 /* Mbed DC fan PWM control.  
00002 
00003 Copyright 2020 Jonathan L. Martin <jon.martini@gmail.com>
00004 
00005 Permission is hereby granted, free of charge, to any person obtaining a copy of 
00006 this software and associated documentation files (the "Software"), to deal in 
00007 the Software without restriction, including without limitation the rights to 
00008 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
00009 the Software, and to permit persons to whom the Software is furnished to do so, 
00010 subject to the following conditions:
00011 
00012 The above copyright notice and this permission notice shall be included in all 
00013 copies or substantial portions of the Software.
00014 
00015 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
00016 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
00017 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
00018 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
00019 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
00020 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
00021 SOFTWARE.
00022 
00023 This library allows setting a minimum threshold for fans to turn on,
00024 but otherwise uses PWM like any other motor.
00025 
00026 */
00027 
00028 #include "DcFan.h"
00029 
00030 #include "mbed.h"
00031 
00032 DcFan::DcFan(PinName pwm, float min_active_pwm):
00033     _pwm(pwm) {
00034 
00035     // Set initial condition of PWM
00036     _pwm.period(0.00005);
00037     _pwm = 0.0;
00038     if(min_active_pwm > 0.0)
00039     {
00040         _min_active_pwm = min_active_pwm;
00041     } else
00042     {
00043         _min_active_pwm = 0.0;
00044     }
00045 }
00046 
00047 void DcFan::speed(float speed) {
00048     // Don't allow an invalid speed
00049     if (speed > 1.0)
00050     {
00051         speed = 1.0;
00052         // TODO warning?
00053     }
00054     if (speed < _min_active_pwm)
00055     {
00056         speed = 0.0;
00057     }
00058     _pwm = speed;
00059 }