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  #1  
Old 12-10-2017, 09:23 AM
TShort TShort is offline
 
Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
Posts: 1,024
Default G3X and GTN 650 lighting / dimmer control

I'm in the process of installing a 3 screen Garmin system (GDU460 x2 and a GDU450) plus a GTN 650.

In terms of dimming / lighting control, the G3X install manual states:

"For providing this reference signal to more than one device, a commercially available regulated backlight voltage reference is recommended."

I found reference to this for dimming the GTN650 in previous posts:

https://www.digikey.com/product-deta...103C-ND/222834

Can I use the same potentiometer to dim the GDU screens? Are others just relying on the automatic dimming, and just having a panel mounted dimmer control for the GTN?

Not sure the best way to handle this.

Thanks in advance.

Thomas
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KUMP - Indianapolis, IN / KAEJ - Buena Vista, CO
RV-10 N410TS bought / flying
RV-8 wings / fuse in progress ... still
1948 Cessna 170 N3949V
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  #2  
Old 12-10-2017, 09:43 AM
krwalsh krwalsh is offline
 
Join Date: Nov 2009
Location: San Francisco, CA
Posts: 351
Default Flight Data Systems

Try one of the lighting controllers from Flight Data Syatems:
http://www.fdatasystems.com/lc-lighting-controllers/
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  #3  
Old 12-10-2017, 10:17 AM
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Jeff A Jeff A is offline
 
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Location: Dallas, TX
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Default

I'm in the process of doing the exact same thing right now. Hope to have the lighting buses calibrated today or tomorrow. It already works well with the GMC307 Autopilot panel.

http://www.aircraftspruce.com/catalo...?clickkey=4042

or

http://www.aircraftspruce.com/catalo...?clickkey=4042
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  #4  
Old 12-10-2017, 10:57 AM
gblanck gblanck is offline
 
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Location: Redwood City, CA
Posts: 98
Default PWM dimmers need a filter

I used the PWM dimmers to control G3x lighting- it didn't work well . Particularly at lower levels the display light level was unstable. Adding a simple RC filter solved the problem. PWM dimmers are effectively digital dimmers providing a variable width pulse, most lighting control inputs are expecting a true analog voltage.
-Greg
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  #5  
Old 12-10-2017, 01:26 PM
tgmillso tgmillso is offline
 
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Location: Launceston, Tasmania, Australia
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Default

I too was going to install separate pots for my Garmin devices as I had the GAD27 with PWM to vary device lighting. Everyone I subsequently spoke with who had GTN650's installed were quite satisfied running of their internal photocells. Thus the only 10k potentiometer I am now installing is the one for Van's LED lighting strip and and all the Garmin devices (GDU460, Aera 660, G5, GTN625, GTR200) are running off their photocells, however I have reserved space in my panel for post if required in the future, but frankly I'd prefer to rely on the photocell as it's one less thing to think about when flying, and when maneuvering the lighting intensity can change quite significantly on the panel as a device goes into or comes out of shadowing.
Tom.
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  #6  
Old 12-10-2017, 02:14 PM
TShort TShort is offline
 
Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
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Default

Thanks for the input.

I had wondered if I could rely on the photo cells to adjust the brightness, but am about to have the panel cut and wanted to add the hole for the potentiometer if necessary.

All I have are the GDU screens, the GTN 650, and a G5, so I guess I could just rely on the internal auto adjust...

I'd read about the FDS boxes, but want to keep things as simple as I can, and would like to avoid mounting another box (things are getting crowded)
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RV-10 N410TS bought / flying
RV-8 wings / fuse in progress ... still
1948 Cessna 170 N3949V
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  #7  
Old 12-10-2017, 04:19 PM
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wjb wjb is offline
 
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Location: Half Moon Bay, CA
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Default

If you're electronics inclined, a simple emitter follower transistor buffer (two components), or a simple unity gain op-amp (one component) would be all that's needed to buffer the output of the pot to supply a low impedance voltage to the G3X and others (I'm building a similar setup).

The pulse width modulated (PWM) signal is NOT the correct one for this HW, but as noted by Greg, a RC low pass filter would serve to convert the PWM into a pseudo-analog signal.
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  #8  
Old 12-10-2017, 06:46 PM
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Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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I always install simple 10k pots for dimmers on big screens and GTN's.

All 3 G3X screens be dimmed from the same pot then another one for the GTN. Flying at night with a screen that is too bright or dim is not the time to try to be setting up an internal dimmer IMO, nothing easier than twisting a knob and setting the brightness level exactly where you want it.
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  #9  
Old 12-10-2017, 07:03 PM
TShort TShort is offline
 
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Location: Indianapolis, IN (KUMP)
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Walt-

So the dimmer referenced in my first post would work (I copied that from another thread where you referenced the dimmers)?

Just connect it to the lighting control pin(s) on the GDUs and /or the GTN, and that's all that is needed? I'm just not 100% clear on how things are connected.

Thanks
Thomas
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KUMP - Indianapolis, IN / KAEJ - Buena Vista, CO
RV-10 N410TS bought / flying
RV-8 wings / fuse in progress ... still
1948 Cessna 170 N3949V
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  #10  
Old 12-10-2017, 07:46 PM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Default

Quote:
Originally Posted by TShort View Post
Walt-

So the dimmer referenced in my first post would work (I copied that from another thread where you referenced the dimmers)?

Just connect it to the lighting control pin(s) on the GDUs and /or the GTN, and that's all that is needed? I'm just not 100% clear on how things are connected.

Thanks
Thomas
Yes.
One end of the pot to 12 volt power (fused or CB); other end to ground; middle ?slider? to GTN(s).
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