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12-10-2017, 09:23 AM
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Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
Posts: 1,024
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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
__________________
Thomas Short
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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12-10-2017, 10:57 AM
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Join Date: Nov 2010
Location: Redwood City, CA
Posts: 98
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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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Greg Blanck
RV-8 Completed March 2014
Redwood City, CA
RV-8 Build Log
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12-10-2017, 01:26 PM
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Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 774
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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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12-10-2017, 02:14 PM
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Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
Posts: 1,024
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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)
__________________
Thomas Short
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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12-10-2017, 04:19 PM
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Join Date: Nov 2012
Location: Half Moon Bay, CA
Posts: 1,035
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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.
__________________
Bill Bencze
N430WB RV-7 #74152 @ KHAF, tip-up; IO-360-M1B; Hartzell CS. !! Phase 1 !!
2357 hrs over 8.5 years to get to flying. Log at: http://rv7.wbencze.com
VAF 2020 donation happily made
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12-10-2017, 06:46 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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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.
__________________
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, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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12-10-2017, 07:03 PM
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Join Date: Jan 2005
Location: Indianapolis, IN (KUMP)
Posts: 1,024
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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
__________________
Thomas Short
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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12-10-2017, 07:46 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Quote:
Originally Posted by TShort
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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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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