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  #21  
Old 03-21-2021, 11:54 PM
jliltd jliltd is offline
 
Join Date: Sep 2013
Location: Rancho San Lorenzo
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Thanks, Walt. I went and changed my settings to match yours. Seems to help. However, I found one issue with the dedicated backlight dimmer. The Bus input voltage provided by the dimmer starts at 0.05 volts but the Garmin minimum dim value Bus Voltage value can only go as low as 0.30 volts in the settings. So if I crank the dimmer all the way counterclockwise for maximum dimming I get the opposite once the value falls below 0.30. In other words the lower output of the mechanical dimmer pot provides a way lower voltage than the Garmin can natively detect, more specifically as soon the voltage goes below 0.30 volts the GDU makes the assumption voltage has been lost and goes to full backlight for what I can only assume is a failsafe mode. So at night I will have to be careful not to turn the dimmer all the way down or I will get full backlight brightness instead of the desired eye-friendly dimming.

Maybe using a lower-sensitivity dimmer pot is more compatible with the G3X display and is friendlier to a pilot who tries to go to minimum screen brightness.
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  #22  
Old 03-22-2021, 06:51 AM
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Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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Quote:
Originally Posted by jliltd View Post
Thanks, Walt. I went and changed my settings to match yours. Seems to help. However, I found one issue with the dedicated backlight dimmer. The Bus input voltage provided by the dimmer starts at 0.05 volts but the Garmin minimum dim value Bus Voltage value can only go as low as 0.30 volts in the settings. So if I crank the dimmer all the way counterclockwise for maximum dimming I get the opposite once the value falls below 0.30. In other words the lower output of the mechanical dimmer pot provides a way lower voltage than the Garmin can natively detect, more specifically as soon the voltage goes below 0.30 volts the GDU makes the assumption voltage has been lost and goes to full backlight for what I can only assume is a failsafe mode. So at night I will have to be careful not to turn the dimmer all the way down or I will get full backlight brightness instead of the desired eye-friendly dimming.

Maybe using a lower-sensitivity dimmer pot is more compatible with the G3X display and is friendlier to a pilot who tries to go to minimum screen brightness.
Jim, you are correct that is somewhat of a limitation on the lower end, never really thought much of it as in reality the display is so dark at that point I don't think you would ever turn it down that far when actually using it at night.

Adding a small resistor to the ground side of the dimmer pot could raise the lower value to say .5 or 1v without much problem. I will experiment with that and perhaps make that a normal addition to the dimmer circuit.
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
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Authorized Garmin G3X Dealer/Installer
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  #23  
Old 03-22-2021, 09:13 AM
PilotjohnS PilotjohnS is offline
 
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Location: Southwest
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Quote:
Originally Posted by Walt View Post
Jim, you are correct that is somewhat of a limitation on the lower end, never really thought much of it as in reality the display is so dark at that point I don't think you would ever turn it down that far when actually using it at night.

Adding a small resistor to the ground side of the dimmer pot could raise the lower value to say .5 or 1v without much problem. I will experiment with that and perhaps make that a normal addition to the dimmer circuit.
This topic comes at a good time. I am just about to wire in my dimmers. I will add 500 ohm, 1/4 watt resistors to the ground end of each 10K pot so that the lowest voltage would be about 0.6V

Edit: no need to add resistor. See post below from Garmin tech support
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Last edited by PilotjohnS : 03-22-2021 at 03:50 PM.
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  #24  
Old 03-22-2021, 10:18 AM
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g3xpert g3xpert is offline
 
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Location: Olathe, KS
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Default Lighting Bus Settings

Quote:
Originally Posted by jliltd View Post
Thanks, Walt. I went and changed my settings to match yours. Seems to help. However, I found one issue with the dedicated backlight dimmer. The Bus input voltage provided by the dimmer starts at 0.05 volts but the Garmin minimum dim value Bus Voltage value can only go as low as 0.30 volts in the settings. So if I crank the dimmer all the way counterclockwise for maximum dimming I get the opposite once the value falls below 0.30. In other words the lower output of the mechanical dimmer pot provides a way lower voltage than the Garmin can natively detect, more specifically as soon the voltage goes below 0.30 volts the GDU makes the assumption voltage has been lost and goes to full backlight for what I can only assume is a failsafe mode. So at night I will have to be careful not to turn the dimmer all the way down or I will get full backlight brightness instead of the desired eye-friendly dimming.

Maybe using a lower-sensitivity dimmer pot is more compatible with the G3X display and is friendlier to a pilot who tries to go to minimum screen brightness.
Jim,

For some reason, Walt's pictures are not showing up for me, what value do you have assigned to Lighting Bus Off Threshold?

Lighting Bus Off Threshold–Sets the lighting bus off threshold input level. At the threshold level, the backlighting is turned on per the Lighting Bus Min setting. Below the threshold level, the backlighting defaults to using the photocell. If the value is set to 0 V, the value will be ignored and the display brightness will remain at the Lighting Bus Min level for any input level between 0 V and the Min Brightness level.

Thanks,

Justin
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  #25  
Old 03-23-2021, 08:41 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Originally Posted by g3xpert View Post
If the value is set to 0 V, the value will be ignored and the display brightness will remain at the Lighting Bus Min level for any input level between 0 V and the Min Brightness level.[/b]

Thanks,

Justin
I am sure this is obvious to most, however, the reason this default exists is that if you lose your dimmer power supply for any reason, you will likely be unable to see your efis during the daylight if you follow the above approach.

I once thought my mnin-x had died. Turns out that I had turned the dimmer way down (via the menu; no dimmer pot) during a night flight and during the day, it looked like the unit wasn't working. Didn't remember the button presses, so had to push it into the hanger to be able to see it well enough to reset the dimmer value.
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Last edited by lr172 : 03-23-2021 at 08:44 AM.
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  #26  
Old 03-23-2021, 09:58 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by g3xpert View Post
Jim,



Lighting Bus Off Threshold–Sets the lighting bus off threshold input level. At the threshold level, the backlighting is turned on per the Lighting Bus Min setting. Below the threshold level, the backlighting defaults to using the photocell. If the value is set to 0 V, the value will be ignored and the display brightness will remain at the Lighting Bus Min level for any input level between 0 V and the Min Brightness level.

Thanks,

Justin
So after looking at this a bit closer, the minimum/off threshold setting of 0.3 works perfect.
If you set it at 0v then the switch back to photocell does not occur when you turn off the dimmer and the display remains dark (to the minimum level set).
When set to 0.3v and you turn off the 'dimmer' the screens revert back to auto-dimming, so I wouldn't change a thing.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1900+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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