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Dimming the G3X

SPark

I'm New Here
Hi there,

I'm currently building a RV7 with a G3X suite. I would like to manually dim the G3X 460 Display, the G5, GTN625, GTR200 and a few LED Light strips.

If possible I would like all the LRUs on one dimmer and the LED lights on another.

My question is, can I dim the LRUs with a simple Potentiometer or do I need other equipment?
 
the garmin components should be done with a potentiometer, its the LED lights that need a PWM (pulse width modulator) to dim them.
 
You might want to consider installing a GAD27 controller, very versatile box for light control, it also does some cool other functions like controlling trim/flap/ldg light wig wag.
 
As Walt mentioned the GAD 27 is a great unit if you are building an aircraft with the G3X Touch. It is a smart dimming controller which has multiple PWM and voltage reference outputs to connect to your different avionics. Using the GAD 27 you can individually balance each circuit and use one, two, or three pots to control these circuits.

In addition, the GAD 27 has a flap controller, extra discrete inputs, wig-wag controller, and trim mixing (to allow you to easily wire your stick grips for trim control)

All of the Garmin LRUs listed above except for the G5 have the lighting bus. The G5 is primarily controlled by the photocell, but also has a manual backlight mode. The G5 was designed this way to bring independence to your backup instrument.

Thanks,
Levi
 
As Walt mentioned the GAD 27 is a great unit if you are building an aircraft with the G3X Touch. It is a smart dimming controller which has multiple PWM and voltage reference outputs to connect to your different avionics. Using the GAD 27 you can individually balance each circuit and use one, two, or three pots to control these circuits.

In addition, the GAD 27 has a flap controller, extra discrete inputs, wig-wag controller, and trim mixing (to allow you to easily wire your stick grips for trim control)

All of the Garmin LRUs listed above except for the G5 have the lighting bus. The G5 is primarily controlled by the photocell, but also has a manual backlight mode. The G5 was designed this way to bring independence to your backup instrument.

Thanks,
Levi

Just wanted to confirm that the G3X dimmer input is looking for variable voltage from the potentiometer.

Larry
 
So I thought I would ask the question here...

instead of starting a new thread.

Garmin says there can be no more than 10mA per pin on the GAD 27.
Garmin also doesn't publish the milliamp ratting for all of their displays. I did find the GDU-4XX are 1mA per unit for the lighting bus but could not find the milliamp rating for anything else.

Seeing that I have 7 units with lighting buses and want all of them on one dimmer...I don't want to exceed the max 10mA draw on one pin and screw up the GAD 27.

Any insights??
 
Michael,

I think you can actually use multiple outputs that are controlled via a single input pot. That allows you to split up the units to different outputs. To be honest I haven't looked at this a ton. I think in general though the DC outputs normally only provide a reference voltage and very little drive current is required. You can also use the PWM outputs for cases where more current is actually required. I think those outputs can drive 500mA.
 
Michael,

I think you can actually use multiple outputs that are controlled via a single input pot. That allows you to split up the units to different outputs. To be honest I haven't looked at this a ton. I think in general though the DC outputs normally only provide a reference voltage and very little drive current is required. You can also use the PWM outputs for cases where more current is actually required. I think those outputs can drive 500mA.

According to the G3X tech I talked to today, I can split up the displays to more pins but that means more dimmer controls. I’d really like to just have on dimmer control for the displays. You’re correct that the PWM outputs can be used for powering LED strip lighting.

You are also correct that it’s just sensing voltage running through the dimmer switches but they can’t have more than 10mA run through an individual pin, or to put it another way, through a single dimmer switch.

My dilemma is how to find or calculate the individual displays milliamp draw.
 
instead of starting a new thread.

Garmin says there can be no more than 10mA per pin on the GAD 27.
Garmin also doesn't publish the milliamp ratting for all of their displays. I did find the GDU-4XX are 1mA per unit for the lighting bus but could not find the milliamp rating for anything else.

Seeing that I have 7 units with lighting buses and want all of them on one dimmer...I don't want to exceed the max 10mA draw on one pin and screw up the GAD 27.

Any insights??

I can't imagine what those 7 units are?
I run 2 screens on one output, a GTN on another, CP lights on another.

Things like audio panel, GMA, GTR units really don't need dimmers, their internal ones work just fine.

I don't think you could ever get everything balanced perfectly using just one dimmer pot.
 
Last edited:
Lighting Bus Input

instead of starting a new thread.

Garmin says there can be no more than 10mA per pin on the GAD 27.
Garmin also doesn't publish the milliamp ratting for all of their displays. I did find the GDU-4XX are 1mA per unit for the lighting bus but could not find the milliamp rating for anything else.

Seeing that I have 7 units with lighting buses and want all of them on one dimmer...I don't want to exceed the max 10mA draw on one pin and screw up the GAD 27.

Any insights??

The lighting bus inputs are typically very high impedance, most installations don't come anywhere near the 10mA limit. If you are putting 7 LRU's on one pin, we can double check just to be safe. Let us know what units you want to connect and we can calculate the max current draw the lighting bus inputs are capable of, collectively.

Thanks,

Justin
 
I can't imagine what those 7 units are?
I run 2 screens on one output, a GTN on another, CP lights on another.

Things like audio panel, GMA, GTR units really don't need dimmers, their internal ones work just fine.

I don't think you could ever get everything balanced perfectly using just one dimmer pot.

The 7 displays are:

GDU460 PFD
GDU470 MFD-1
GDU470 MFD-2
GNX375
GTR200B
GMC507
GI260

So the interconnect drawing I have from SteinAir shows all those units connected to dimmers through the GAD 27.

I never considered just having the GDUs on the dimmer and the rest operated on the photocell. You're saying that setup works OK.

If everything not on a dimmer could be adjusted with the setup mode to be not too bright at night... that could work...


The lighting bus inputs are typically very high impedance, most installations don't come anywhere near the 10mA limit. If you are putting 7 LRU's on one pin, we can double check just to be safe. Let us know what units you want to connect and we can calculate the max current draw the lighting bus inputs are capable of, collectively.

Thanks,

Justin
Walt recommended having just the GDUs on dimmers.

But, it would seem that if the manual gives us a limit on the milliamps through a single pin, the information should be available somewhere in the install manuals. The only reference I could find was the GDUs page 26-26 highlighted in green. The other displays did not have this info that I could find.

By the way, what does that sentence highlighted in blue mean?? It seems to suggest that more than on display per pin needs some sort of regulator.
 

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The 7 displays are:

GDU460 PFD
GDU470 MFD-1
GDU470 MFD-2
GNX375
GTR200B
GMC507
GI260

So the interconnect drawing I have from SteinAir shows all those units connected to dimmers through the GAD 27.

I never considered just having the GDUs on the dimmer and the rest operated on the photocell. You're saying that setup works OK.

If everything not on a dimmer could be adjusted with the setup mode to be not too bright at night... that could work...



Walt recommended having just the GDUs on dimmers.

But, it would seem that if the manual gives us a limit on the milliamps through a single pin, the information should be available somewhere in the install manuals. The only reference I could find was the GDUs page 26-26 highlighted in green. The other displays did not have this info that I could find.

By the way, what does that sentence highlighted in blue mean?? It seems to suggest that more than on display per pin needs some sort of regulator.

In your installation, the regulated backlight voltage reference is the GAD 27. You can use a simple rheostat to provide a reference voltage to a GDU, but you would not want to use the same to provide a reference voltage to several different units, you want to use a GAD 27 or something similar.

Thanks,

Justin
 
I have a GDU460, a GPS 175, A GTR 200 that I would like to all dim on one 1.5A rheostat. I am looking for the amp draw on the dimming wires and can't seem to find it. I am not installing a GAD 27. Would that 1.5A be sufficient to dim them all together?

I also have a GMA 254 and a GMC 507 but from what I read here should leave them dim on their own with the internal automatic dimmer?
 
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