4-11: Day/Night Mode Colors and Backlight Dimming

Powervision provides a Day and a Night operating mode each with their own backlight settings and color schemes. The color scheme is inherent in the graphical widgets used in the page designer. There is typically a day color and a night color for the various elements that comprise the widget. This is designed so a display can instantly change to a color scheme appropriate for the ambient light conditions. For example when operating a display at night to preserve the operators night vision the display backlight should be dim and the colors should be blacks and darker shades of greens and or reds. The colors you choose will allow a certain amount of the white backlight to pass through, for night mode choose colors that have low RGB values, especially Blue values. 

Download the Example created in 2.9.23044 for a PV780B.

Switching Day/Night Modes

Use a calculation event tied to a menu button or connected to the status of a digital input to change the value of the system variable Day/Night between 1 and 2. See Enumeration tab.

Backlight Dimming

There are separate dimming variables for day mode and night mode, these are Brightness.Day and Brightness.Night . Values are in units of percent. Set these dimming values independent of each other. Night mode works bets with low dimming values around 20-30%. After changing values the variables must be stored in non-volatile memory using the NVMgr->Save action. Verify the variables Save Values property is set to "Survives Power Cycle".  After making changes call the action System->UpdateBacklight to pass the new variable value down to the driver.

Startup Brightness

Starting in Powervision 7, Startup Brightness was introduced to allow the bootloader to use a brightness level separate from the runtime brightness. This brightness level starts at power up and continues through the boot cycle until the CCM is running and the event Screen.ScreenReady fires.

Set the variable Startup.Brightness to the desired value then call the action SaveStartupData(Empty) to save the value.

Day/Night Mode Color Selection

Set the desired colors for each widget for day and night modes. Run through the entire list of widget properties with "Show Advanced" selected to verify they are all set. Keep the color scheme consistent.

Simulating Day/Night Mode

To verify the colors have all been properly set, select the sun icon at the bottom of the window to toggle between day and night modes. The widget colors will change to the mode selected.

Blackout Mode

To prevent the screen from dimming all the way off and the operator not being able to recover, the lowest actual dimming value is limited between 5-10% even though the variable is set to 0%. To allow full blackout the variable BlackoutMode.Enabled must be set to "1". To power up in backlight "off" mode enable this variable and save it to non-volatile memory and set the dimming level to 0%. This is sometimes needed where night vision goggles are used. Use care when implementing this feature to provide a simple way to restore the backlight.

Startup Brightness must also be set when using Powervision 7.x or newer.

Backlight On/Off Actions

These two System Manager Application actions allow you to turn the backlight completely off and back on. They do not survive a power cycle and the backlight will default to the on condition.

Auto Brightness

This feature applies to displays equipped with a Ambient Light Sensor (ALS) like the PV-P70 and U35 displays. When Auto Brightness is turned on, the display backlight will automatically dim based on the ALS value, here is a description of how it operates.

• Variables Used
  • System.AutoBrightness: 0 = Off, 1 = Enabled
  • System.ALSValue: see chart below                        

• Auto Brightness affects only the Brightness.Day variable as shown in the table.
• In Auto Brightness mode, the Brightness.Day value is used for both day mode and night mode.
• When in Day Mode and turning Auto Brightness Off, the Brightness.day variable must be manually restored to a desired value and the action UpdateBacklight called to set the new brightness value.
• When in Night Mode and turning Auto Brightness Off, only the action UpdateBacklight needs to be called to set the backlight to the current Brightness.Night value.

Color Selection Tip

The higher the RGB value the more  backlight will pass through, for example white has a RGB value of 255,255,255 whereas black has values of 0,0,0 (no light). To see the RGB value of a color select the desired color from the standard list then switch to the Color Selector tab, the RGB values will be displayed. This allows you to quickly determine how bright a color will be for day or night use.