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G3X and dimmers

flysrv10

Well Known Member
Anyone connecting G3x to dimmers? If so, what brand and model dimmer you would recommend. Thank you.
 
I'm still waiting on my panel, so I have no experience with G3Xs.

But I have a ton of experience with G1000 screens in certified planes. I know the G1000 has a menu for dimmers and is controlled by those settings with itself.

Is the G3x different and requires an external switch?
 
Just go to Mouser or Digikey and order any 10K, panel mount, single turn, potentiometer. Bourns makes high quality units.
 

So is it for sure 1K?

I've been chasing an issue with mine since the panel re-do 3 years ago. It is SUPER sensitive, and only works through ~5-10% of the range. I've not troubleshot it much as I don't need to adjust the lighting often.

I just looked, and I bought that same model in 10K.

So, if it is supposed to be 1K, I may have found the problem...
 
So is it for sure 1K?

I've been chasing an issue with mine since the panel re-do 3 years ago. It is SUPER sensitive, and only works through ~5-10% of the range. I've not troubleshot it much as I don't need to adjust the lighting often.

I just looked, and I bought that same model in 10K.

So, if it is supposed to be 1K, I may have found the problem...

I think I switched to the 1K models to help with resolution but the 10k should work just as good and I believe it is what Garmin calls out.
More importantly you also have to go into the dimmer menus and adjust the curves/set points to make them operate properly.
 
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These dimmers were recommended to me by the large avionics shop doing my harness. I bought the two pot model for my flood lights I have in my RV8. you can get one to four circuits. They will prefab the harness for an extra fee if you want them to.

https://www.aircraftspruce.com/catalog/elpages/sptdimming.php

G3X and GAD 27...these are the dimmers SteinAir sent me for my setup.

You don't need big voltage regulating dimmers for the G3X/GTN equipment, the above are for light bulb style dimming where the unit being dimmed is actually drawing current from the dimmer to control it.

The G3X/GTN stuff is voltage sensing and doesn't actually draw any current from the dimmer circuit, it just tracks the voltage which is why a simple pot works fine.
 
G3X Touch Backlight

So is it for sure 1K?

I've been chasing an issue with mine since the panel re-do 3 years ago. It is SUPER sensitive, and only works through ~5-10% of the range. I've not troubleshot it much as I don't need to adjust the lighting often.

I just looked, and I bought that same model in 10K.

So, if it is supposed to be 1K, I may have found the problem...

Hey Thomas,

Can you email us a screenshot of your Backlight Configuration Menu? We can take a look at the settings and see if there is any room for improvement.

Thanks,

Justin
 
GTN Self dimming?

You don't need big voltage regulating dimmers for the G3X/GTN equipment, the above are for light bulb style dimming where the unit being dimmed is actually drawing current from the dimmer to control it.

The G3X/GTN stuff is voltage sensing and doesn't actually draw any current from the dimmer circuit, it just tracks the voltage which is why a simple pot works fine.

Can you go in and dim the GTN or G3X within the unit? If so, is there a real need other than convenience to have the dimmer?
 
You don't need big voltage regulating dimmers for the G3X/GTN equipment, the above are for light bulb style dimming where the unit being dimmed is actually drawing current from the dimmer to control it.

The G3X/GTN stuff is voltage sensing and doesn't actually draw any current from the dimmer circuit, it just tracks the voltage which is why a simple pot works fine.

Well bummer... these dimmers were expensive...

So will these work with the GAD 27?
 
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Every time I have played with my external dimmer pot during daylight my G3X screen intantly goes so dim it is effectively blacked out where I cannot see anything. Not just gradually but instantaneously. Then the dimmer pot does nothing to help bring it back up. I have to pull the breaker on the GDU dispaly and then reset the breaker to re-boot it in flight. As such I don't ever touch the dimmer knob any more as I would rather not loose primary flight instruments in the air.
 
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Check your settings Jim, here's a couple of pics to help, these are my settings and should work for most foks, mine works perfect, the first 2 pics are with dimmer bus off, the last pic is with the dimmer 'bus' on at about the 50% dim level.

i-4bdf2hv-XL.jpg


i-6JLHq2d-XL.jpg


i-bCt2J87-XL.jpg
 
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Hey Thomas,

Can you email us a screenshot of your Backlight Configuration Menu? We can take a look at the settings and see if there is any room for improvement.

Thanks,

Justin

Justin-

Will do - thanks for the message.
This has been on my to-do list for a while, but I just keep putting it off and using the time to fly instead!
I'll get some screenshots when I am at the airport next.

Thomas
 
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.
 
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.
 
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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Lighting Bus Settings

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
 
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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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.
 
Dumb wiring question on the GTN650 lighting bus. For the LO circuit, does that mean it provides the ground to the Pot switch and there is no need to ground the Pot switch to a grounding bus?

Seems a bit different from the G3X which only has the one output to the Pot switch
 

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