How can I write a Delphi program to control the CPU fan speed and monitor the temperature?

Question

I want to use Delphi to create a program that controls the fan speed of my computer and monitors the temperature.

What API calls are involved in doing that?

Are there any good code samples that you can share?

Answer 1

You can use the WMI classes Win32_TemperatureProbe and Win32_Fan, from delphi you must import the Microsoft WMIScripting V1.x Library using Component->Import Component->Import type library->Next->"Select the library"->Next->Add unit to project->Finish.

See this code. is just a simple example.

program GetWMI_Info;

{$APPTYPE CONSOLE}

uses
  ActiveX,
  Variants,
  SysUtils,
  WbemScripting_TLB in '..\..\..\Documents\RAD Studio\5.0\Imports\WbemScripting_TLB.pas';

procedure ShowTemperatureInfo();
var
  WMIServices: ISWbemServices;
  Root       : ISWbemObjectSet;
  Item       : Variant;
  I          : Integer;
begin
 {
 http://msdn.microsoft.com/en-us/library/aa394493%28VS.85%29.aspx
 The Win32_TemperatureProbe  WMI class represents the properties of a temperature sensor (electronic thermometer).
 Most of the information that the Win32_TemperatureProbe WMI class provides comes from SMBIOS.
 Real-time readings for the CurrentReading property cannot be extracted from SMBIOS tables.
 For this reason, current implementations of WMI do not populate the CurrentReading property.
 The CurrentReading property's presence is reserved for future use.
 }

  Writeln('Temperature Info');
  Writeln('----------------');

  WMIServices := CoSWbemLocator.Create.ConnectServer('.', 'root\cimv2','', '', '', '', 0, nil);
  Root  := WMIServices.ExecQuery('Select * FROM Win32_TemperatureProbe','WQL', 0, nil);
  for I := 0 to Root.Count - 1 do
  begin
    Item := Root.ItemIndex(I);
      Writeln('Accuracy                        '+VarToStr(Item.Accuracy));
      Writeln('Availability                    '+VarToStr(Item.Availability));
      Writeln('Caption                         '+Item.Caption);
      Writeln('Config Manager Error Code       '+VarToStr(Item.ConfigManagerErrorCode));
      Writeln('Config Manager User Config      '+VarToStr(Item.ConfigManagerUserConfig));
      Writeln('Creation Class Name             '+VarToStr(Item.CreationClassName));
      Writeln('Current Reading                 '+VarToStr(Item.CurrentReading));
      Writeln('Description                     '+VarToStr(Item.Description));
      Writeln('Device ID                       '+VarToStr(Item.DeviceID));
      Writeln('Error Cleared                   '+VarToStr(Item.ErrorCleared ));
      Writeln('Error Description               '+VarToStr(Item.ErrorDescription));
      Writeln('Install Date                    '+VarToStr(Item.InstallDate));
      Writeln('Is Linear                       '+VarToStr(Item.IsLinear));
      Writeln('Last Error Code                 '+VarToStr(Item.LastErrorCode));
      Writeln('Lower Threshold Critical        '+VarToStr(Item.LowerThresholdCritical));
      Writeln('Lower Threshold Fatal           '+VarToStr(Item.LowerThresholdFatal));
      Writeln('Lower Threshold NonCritical     '+VarToStr(Item.LowerThresholdNonCritical));
      Writeln('Max Readable                    '+VarToStr(Item.MaxReadable));
      Writeln('Min Readable                    '+VarToStr(Item.MinReadable));
      Writeln('Name                            '+VarToStr(Item.Name));
      Writeln('Nominal Reading                 '+VarToStr(Item.NominalReading));
      Writeln('Normal Max                      '+VarToStr(Item.NormalMax));
      Writeln('Normal Min                      '+VarToStr(Item.NormalMin ));
      Writeln('PNP Device ID                   '+VarToStr(Item.PNPDeviceID));
      Writeln('Power Management Capabilities   '+VarToStr(Item.PowerManagementCapabilities));
      Writeln('Power Management Supported      '+VarToStr(Item.PowerManagementSupported));
      Writeln('Resolution                      '+VarToStr(Item.Resolution));
      Writeln('Status                          '+VarToStr(Item.Status));
      Writeln('Status Info                     '+VarToStr(Item.StatusInfo));
      Writeln('System Creation Class Name      '+VarToStr(Item.SystemCreationClassName));
      Writeln('System Name                     '+VarToStr(Item.SystemName));
      Writeln('Tolerance                       '+VarToStr(Item.Tolerance));
      Writeln('Upper Threshold Critical        '+VarToStr(Item.UpperThresholdCritical));
      Writeln('Upper Threshold Fatal           '+VarToStr(Item.UpperThresholdFatal));
      Writeln('Upper Threshold NonCritical     '+VarToStr(Item.UpperThresholdNonCritical));
      Writeln('');
  end;
end;

procedure  ShowCPUFanInfo();
var
  WMIServices: ISWbemServices;
  Root       : ISWbemObjectSet;
  Item       : Variant;
  I          : Integer;
begin
 {
  http://msdn.microsoft.com/en-us/library/aa394146%28VS.85%29.aspx
  The Win32_Fan WMI class represents the properties of a fan device in the computer system. For example, the CPU cooling fan.
 }
  Writeln('CPU FAN Info');
  Writeln('----------------');
  WMIServices := CoSWbemLocator.Create.ConnectServer('.', 'root\cimv2','', '', '', '', 0, nil);
  Root  := WMIServices.ExecQuery('Select * FROM Win32_Fan','WQL', 0, nil);
  for I := 0 to Root.Count - 1 do
  begin
    Item := Root.ItemIndex(I);

    Writeln('ActiveCooling                     '+VarToStr(Item.ActiveCooling));
    Writeln('Availability                      '+VarToStr(Item.Availability));
    Writeln('Caption                           '+VarToStr(Item.Caption));
    Writeln('Config Manager ErrorCode          '+VarToStr(Item.ConfigManagerErrorCode));
    Writeln('Config Manager UserConfig         '+VarToStr(Item.ConfigManagerUserConfig));
    Writeln('Creation ClassName                '+VarToStr(Item.CreationClassName));
    Writeln('Description                       '+VarToStr(Item.Description));
    Writeln('DesiredSpeed                      '+VarToStr(Item.DesiredSpeed));
    Writeln('DeviceID                          '+VarToStr(Item.DeviceID));
    Writeln('ErrorCleared                      '+VarToStr(Item.ErrorCleared));
    Writeln('ErrorDescription                  '+VarToStr(Item.ErrorDescription));
    Writeln('InstallDate                       '+VarToStr(Item.InstallDate));
    Writeln('LastErrorCode                     '+VarToStr(Item.LastErrorCode));
    Writeln('Name                              '+VarToStr(Item.Name));
    Writeln('PNPDeviceID                       '+VarToStr(Item.PNPDeviceID));
    Writeln('PowerManagement Capabilities      '+VarToStr(Item.PowerManagementCapabilities));
    Writeln('PowerManagement Supported         '+VarToStr(Item.PowerManagementSupported));
    Writeln('Status                            '+VarToStr(Item.Status));
    Writeln('StatusInfo                        '+VarToStr(Item.StatusInfo));
    Writeln('SystemCreation ClassName          '+VarToStr(Item.SystemCreationClassName));
    Writeln('SystemName                        '+VarToStr(Item.SystemName));
    Writeln('VariableSpeed                     '+VarToStr(Item.VariableSpeed));
    Writeln('');
  end;

End;


begin
  try
    CoInitialize(nil);
        ShowTemperatureInfo();
        ShowCPUFanInfo();
        Readln;
    CoUninitialize;
  except
    on E:Exception do
    Begin
        CoUninitialize;
        Writeln(E.Classname, ': ', E.Message);
        Readln;
    End;
  end;
end.

Answer 2

You can use WMI to gain access to the fan speed (and other statistics such as temperature). A good example of using WMI in Delphi is available from Magenta Systems.