FYI About LED's and GAD27

[Desert Rat]

I ran across something that was new to me and thought I'd throw it out there in case anybody else runs into the same issue;

My cabin lighting is 3 of the LED strips that Steinair sells, run through the 3 knob dimmers to the GAD27.

I hooked up the first one and it was great!

Hooked up the other two and suddenly all 3 of them were only about 1/2 as bright. What the heck?

Got into the book and discovered the lighting outputs for the GAD27 are only 500 millliamps and the strips are approx 800 milliamps per meter.

Ahah! I reasoned that I was pulling too many amps and chopped off the appropriate amount from each strip to get them under 500 milliamps each. Now we're cooking, right?

Nope, still only about 1/2 as bright as before. Again, what the heck? I thought maybe I'd fried something in the lighting circuit on the GAD, but garmin swapped it out with a loaner and nope, still the same thing.

Long story short, I put this on the back burner for a while and only got back to it yesterday; but when all was said and done, the resolution turned out to be simple.

When I originally hooked up all 3, I popped the fuse to the lighting circuit. You would think that if that happened, they would go dark and stay that way, but there was still enough residual current coming through the GAD (?) that they were lighting up, just at about 1/2 of the brightness. I'll be the first to admit that have no explanation for why it works this way, but it does.

So, the moral of the story is that when you're troubleshooting, even if you think theres' no way its causing your issue, start with the simple stuff first

 

[9GT]

I ran across something that was new to me and thought I'd throw it out there in case anybody else runs into the same issue;

My cabin lighting is 3 of the LED strips that Steinair sells, run through the 3 knob dimmers to the GAD27.

I hooked up the first one and it was great!

Hooked up the other two and suddenly all 3 of them were only about 1/2 as bright. What the heck?

Got into the book and discovered the lighting outputs for the GAD27 are only 500 millliamps and the strips are approx 800 milliamps per meter.

Ahah! I reasoned that I was pulling too many amps and chopped off the appropriate amount from each strip to get them under 500 milliamps each. Now we're cooking, right?

Nope, still only about 1/2 as bright as before. Again, what the heck? I thought maybe I'd fried something in the lighting circuit on the GAD, but garmin swapped it out with a loaner and nope, still the same thing.

Long story short, I put this on the back burner for a while and only got back to it yesterday; but when all was said and done, the resolution turned out to be simple.

When I originally hooked up all 3, I popped the fuse to the lighting circuit. You would think that if that happened, they would go dark and stay that way, but there was still enough residual current coming through the GAD (?) that they were lighting up, just at about 1/2 of the brightness. I'll be the first to admit that have no explanation for why it works this way, but it does.

So, the moral of the story is that when you're troubleshooting, even if you think theres' no way its causing your issue, start with the simple stuff first

Timely post Terry. I am deep into GAD27/LED dimmer wiring currently. Good info to know.

 

[Desert Rat]

Great, hopefully it helps eliminate some head scratching, if not for you, then maybe for somebody in the future.

Just to be clear, the GAD27 output is 500 milliamps per channel. 3 channels, one for each dimmer knob that stein sells. I put a meter on the LED strips and as shipped, they came in at about 750 milliamps each. I lopped about 8" off each one to get them below 500 milliamps and they are really bright when turned way up.

Also, you probably already know this, but just in case; you don't need an off switch, if you got into the config menu you can set it up so that when the knobs are turned all the way left the output through the GAD is zero, with linear set points from there. I just went with two set points so you get a nice linear brightness from zero to 100%.

Here's a picture of them testing at 100% brightness. In the picture the white is overwhelming the blue, but in reality they are both super bright.

 

[agent4573]

I just want to correct something you said, the GAD27 doesn't output anything for lighting control. It can SINK up to 500 mA per channel. It acts a a ground, not as a supply. So saying it can "provide" 500 mA is incorrect. If you've got the positive wire hooked up to the GAD27 expecting it to source current, you're going to have a hard time getting it to work. I know this because I absolutely hooked it up backwards at first.

 

[Desert Rat]

You are correct. That’s for bringing up that point

 

[9GT]

Great, hopefully it helps eliminate some head scratching, if not for you, then maybe for somebody in the future.

Just to be clear, the GAD27 output is 500 milliamps per channel. 3 channels, one for each dimmer knob that stein sells. I put a meter on the LED strips and as shipped, they came in at about 750 milliamps each. I lopped about 8" off each one to get them below 500 milliamps and they are really bright when turned way up.

Also, you probably already know this, but just in case; you don't need an off switch, if you got into the config menu you can set it up so that when the knobs are turned all the way left the output through the GAD is zero, with linear set points from there. I just went with two set points so you get a nice linear brightness from zero to 100%.

Here's a picture of them testing at 100% brightness. In the picture the white is overwhelming the blue, but in reality they are both super bright.

I am using one pot for the IP glare shield red lighting and the white interior lighting. Using a DPDT with center off to toggle between red and white led strips.

 

[jliltd]

Are LED strip lights under the glareshield really necessary with the advent of glass panels? I totally get it with steam gauges. But with digital instruments and screens this would be analogous to shining a light on a TV screen in the same way one would illuminate a painting. If nothing else limit the LED strip lighting to darkened areas away from glass panel displays.

 

[JDA_BTR]

I use the red glare shield led strip at night but very dimly since it helps see the switches better and a little cabin light. I never installed true cabin lights because the led strip is so bright it does great work turned all the way up but I only do that on the ground.

 

[Desert Rat]

Are LED strip lights under the glareshield really necessary with the advent of glass panels? I totally get it with steam gauges. But with digital instruments and screens this would be analogous to shining a light on a TV screen in the same way one would illuminate a painting. If nothing else limit the LED strip lighting to darkened areas away from glass panel displays.

I get your analogy, but it's assuming I want light up the screens. Not true, I want to light up the switches and breakers. Also nice to have an unobtrusive way to light up the cockpit for writing down a clearance or opening up a candy bar without having to hold a flashlight in my mouth.

But you're right. It's possible there will be enough light coming off the EFIS screens that I won't even need these LEDS, but I really don't know that one way or another so I installed them.

 

[PilotjohnS]

Pilotjohns

One could add a resistor in line with the LED strip to reduce the current draw (and the brightness) my strips are so bright I dont see how anyone would want them so bright as to pull 600 mA. I guess it depends on the layout. JMHO

I have my instruments dimmers set so that all the way left defaults to the intermal sensor and no longer use the pot setting. Great feature.

 

[9GT]

Are LED strip lights under the glareshield really necessary with the advent of glass panels? I totally get it with steam gauges. But with digital instruments and screens this would be analogous to shining a light on a TV screen in the same way one would illuminate a painting. If nothing else limit the LED strip lighting to darkened areas away from glass panel displays.

With the GAD 27 and dimmer pots, I can adjust the amount of light I want/need to whatever brightness settings I configure in the G3X. Red for night flying and the white for lighting up the front cockpit area. I also have a white led strip in the baggage compartment. Will I ever need it or use it?,,,,maybe maybe not. But it’s there in case I ever do. I also have a dimmer pot for the avionics displays that may never get used.