Sleep apnea is not normally a good thing, but I needed to prevent our workstations from going to sleep. Our domain workstations were going to sleep in the middle of 3rd party model runs, and group policy overrode any local power settings.

What problem does this solution solve?

This Visual Basic (2010) utility uses the SetThreadExecutionState API to inform the system that it is in use, thereby preventing the system from entering sleep or turning off the display while the application is running. The system automatically detects activities such as local keyboard or mouse input, server activity, and changing window focus (which all will keep a system from going to sleep). But disk, CPU activity and video display are activities that are not automatically detected (and a long running process is not enough to keep a system awake).

How does the code work?

The application calls the SetThreadExecutionState API once when the form is loaded. The system will not sleep (or turn off the display) as long as this application is running.

  ' API call to prevent sleep (until the application exits)
  Private Declare Function uses the SetThreadExecutionState Lib "kernel32" (ByVal esflags As EXECUTION_STATE) As EXECUTION_STATE

  ' Define the API execution states
    ES_SYSTEM_REQUIRED = &H1    ' Stay in working state by resetting display idle timer
    ES_DISPLAY_REQUIRED = &H2   ' Force display on by resetting system idle timer
    ES_CONTINUOUS = &H80000000  ' Force this state until next ES_CONTINUOUS call and one of the other flags are cleared
  End Enum

  ' Prevents sleep as form loads
  Private Sub Form1_Load(sender As Object, e As System.EventArgs) Handles Me.Load
  End Sub

  ' Call API - force no sleep and no display turn off
  Private Function No_Sleep() As EXECUTION_STATE
  End Function

API execution states (ES_SYSTEM_REQUIRED, ES_DISPLAY_REQUIRED, and ES_CONTINUOUS) are explained at

A button on the form flashes red every five seconds (users like to know something is happening)


  ' Flash button (so users know it's still running)
  Private Sub NoSleep_Timer_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NoSleep_Timer.Tick
    Dim Save_Backcolor As Color = Status_Button.BackColor
    Status_Button.BackColor = Color.Red
    Thread.Sleep(500)   ' keeps button red for time
    Status_Button.BackColor = Save_Backcolor
  End Sub

Users can double click on the application to minimize the application to the system tray. A balloon tip is displayed when it's minimized so users know which icon is used.


  ' Minimize to tray if form double clicked
  Private Sub Form1_DoubleClick(sender As Object, e As System.EventArgs) Handles Me.DoubleClick
  End Sub

  ' hide application form
  Private Sub MinimizeAppToTray()
    NoSleep_NotifyIcon.Visible = True
    ' Show ballon text for time when app minimized
  End Sub

Users can double click on the system tray icon to show the application window again, or right click on the icon to close the application (see full source code for these functions).

Points of Interest

This was tested and works on Windows XP, (and both 32/64 bit) Vista and Windows 7 systems.

Here are the check sums of the no_sleep.exe compiled application (VERIFY FILE INTEGRITY PRIOR TO EXECUTING, or recompile to be on the safe side).

		MD5				SHA-1
-------------------------------- ----------------------------------------
8397eb0bd800b2ed16dce95c92d2646c 0e679fcb8ef3e34f7528ecb72f963b7d33810a37


Version 1 posted 25 Nov 2011

Version 2 posted 27 Nov 2011 (changed source code zip file name - with same code)

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