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  #1  
Old 08-10-2018, 01:52 PM
8 Builder 8 Builder is offline
 
Join Date: Aug 2014
Location: Lowell, MA
Posts: 62
Default GAD 27 and LEDs

I have been researching LED light strips to use in the cockpit that are connected through the GAD 27. The plan is for two dimmer circuits. One under the glare shield and one for cockpit "courtesy" lights, probably under the arm rests. The problem is that the limit for each dimmer circuit is 500 mA. From what I can see, that is not too much light in lumens because you will exceed the 500 mA limit if you use over 2 feet of a standard brightness light strip. That is about equal to a 40 watt incandescent light bulb. I realize that the lights don't need to be bright; especially for night flights but how do users of the GAD 27 feel about the amperage limit and what type of SMD strip lights have you chosen?

Thanks,
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  #2  
Old 08-10-2018, 09:23 PM
Scott Hersha Scott Hersha is offline
 
Join Date: Jan 2005
Location: Cincinnati, OH
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Default

Iím able to dim about 3 feet of LED light strip through the GAD27 using one of the PWM outputs. It dims fine, from full bright down to almost zero. I use the DC outputs to dim my screens. All are controlled with a dimmer kit with 3 controls I got from Stein.
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  #3  
Old 08-11-2018, 07:10 PM
KeithB KeithB is offline
 
Join Date: Mar 2014
Location: Granbury, TX
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Default

I purchased the LED strip from Van's (red and white) and control it using a GAD 27. I have had no issues through the full range. To the previous post, I would add that my range includes a cut-off that allows me to turn the LED strip completely OFF.

I use a DC circuit for the screens (dual G3X touch, GTN 650) on dimmer 1, and another DC for the buttons/key (on the GTN 650, GMA 245, etc.) on dimmer 2. I use the PWM circuit on dimmer 2 for the LED lights in my switches, and another PWM for the LED strip on dimmer 3. On the strip, the white light is powered by a Cabin Lights circuit, the red light is powered by a Panel Lights circuit. With Dimmers 2 and 3 to OFF, only the screens and buttons (G3X, GTN, GMA, GMC) are lit - the rest of the panel is dark.
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  #4  
Old 08-11-2018, 07:29 PM
tgmillso tgmillso is offline
 
Join Date: Nov 2012
Location: Launceston, Tasmania, Australia
Posts: 597
Default

I've got a Van's white strip connected to a GAD27. The current draw is 0.2A at what I would consider a "normal" light setting, and 0.6A at full output (way too bright for normal night ops). I utilize a Sparkfun 10k rotary linear pot to adjust the light intensity through the GAD27.
https://www.sparkfun.com/products/9939
https://www.sparkfun.com/products/9998
Tom.
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  #5  
Old 08-13-2018, 05:36 PM
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g3xpert g3xpert is offline
 
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Location: Olathe, KS
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Quote:
Originally Posted by 8 Builder View Post
I have been researching LED light strips to use in the cockpit that are connected through the GAD 27. The plan is for two dimmer circuits. One under the glare shield and one for cockpit "courtesy" lights, probably under the arm rests. The problem is that the limit for each dimmer circuit is 500 mA. From what I can see, that is not too much light in lumens because you will exceed the 500 mA limit if you use over 2 feet of a standard brightness light strip. That is about equal to a 40 watt incandescent light bulb. I realize that the lights don't need to be bright; especially for night flights but how do users of the GAD 27 feel about the amperage limit and what type of SMD strip lights have you chosen?

Thanks,
Hello Rich,

There is a way to configure the system to make sure you don't exceed the current limitations and possibly damage a lighting bus output.

The cockpit lighting configuration page example on page 35-176 of the Rev. AF G3X Installation Manual explains how to configure the lighting bus output.

The potentiometer control is connected to the 12V reference signal, and provides a 0-12V input to the GAD 27. In a typical configuration, when the control is turned to full brightness and outputs 12V, the output is configured for 100%, which outputs maximum voltage to the light strip.

Since you already know that 100% (maximum voltage) would cause the light strip to draw more than 500 mA, you can set this output percentage to something less than 100% to keep the current draw to under 500 mA.

For example, if you find that a 70% output causes the measured current for the light strip to be 500 mA, you would want to set the output associated with the 12V input from the control pot to be 70%.

As you have said, you likely will need far less than the maximum output of this lighting strip for night operations, so there is no penalty to setting the maximum output to something less than 100% to protect your GAD 27 from damage.

Let us know if you have any questions.

Thanks,
Steve
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Last edited by g3xpert : 08-13-2018 at 07:41 PM.
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  #6  
Old 08-13-2018, 06:36 PM
leok leok is offline
 
Join Date: Apr 2013
Location: Clarkston, MI
Posts: 209
Default Could use a transistor

You could also use the GAD27 output to drive the bias on a transistor. With that set up, you could drive most any LED set up you would ever want in your aircraft
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  #7  
Old 08-13-2018, 07:59 PM
8 Builder 8 Builder is offline
 
Join Date: Aug 2014
Location: Lowell, MA
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Thanks for all the responses. I will have to look at the installation manual on how this will be set up. Will I have to put a meter on the light to measure amp draw or is that part of the setup information as you configure the light output? Asking a lot I know.
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  #8  
Old 08-14-2018, 05:19 AM
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g3xpert g3xpert is offline
 
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Location: Olathe, KS
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Quote:
Originally Posted by 8 Builder View Post
Thanks for all the responses. I will have to look at the installation manual on how this will be set up. Will I have to put a meter on the light to measure amp draw or is that part of the setup information as you configure the light output? Asking a lot I know.
Hello Rich,

You would need to monitor the current with your multi-meter.

Thanks,
Steve
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Please email us for support instead of using Private Messaging due to the limitations of the latter.
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