We need to talk about the dimming problem

[chriscalandro]

I have been complaining to Dynon about this for a while, but at this point I don't have a lot of confidence in the code behind the dimming functions, to the point where now I believe it's a safety issue.

I routinely fly over the everglades at night. So far I have never been able to get the screens to dim below 3.5%, which for that flight is still about 1.5% too bright. The other night's flight had be dodging some weather I couldn't see because of the glare from the screens and forced me to turn them off and fly with the D10 so I could see outside.

First thing I did when I got back was wire a dimmer to the displays (I have 2 HDX displays) so I no longer had to rely on the auto dimming functions, that's where things got interesting. With the dimmer all the way down the screen will not dim below 4.5%. The voltage on the display reads 0. Currently I have minimum brightness at 0v and 25% at 1v. Then I turn off the right side display - target brightness goes to 0. Turn the right display back on, target brightness goes to 4.5. Voltage on both displays is reading 0 and the targets are all set exactly the same. I repeat the same test the other direction, turn the left screen off, right side goes to 0% brightness. Turn it back on, back to 4.5. I put my finger over the ambient light sensor (hanger is closed, it's 10pm, and the lights are off) screens dim to 4%. Remove my finger, Screen goes back to 4.5. Double check my settings and 100% both displays are set to external for dimmer source.

I need 2%. That's where flying over the everglades on a moonless night is not a full IFR trip on a clear night. The dim functions on these displays in my opinion does not function properly. In addition, I do not want to ever see 0% as I did when I turned one of the displays off. I want to be able to set a minimum brightness target along with my voltage targets.

Anybody have any thoughts or have this problem? The everglades at night is very dark. If I can get these displays dim enough, for sure I can see on a clear moonlit night, probably I can see on a no moon night. Right now I can't see anything on either without turning off my HDX displays and flying with the D10.

 

[DBRV10]

So have you previously with the auto dim manually turned the back light down via the DIM function?

I have done a bit of night flying with the HDX and never found this a problem when dimmed down.

One more thing to consider. What other instrument panel lighting, or cockpit lighting are you using? The reason I say this is as you have more panel or cockpit light, even the red light, the HDX will ramp up. So it is a force feedback loop you get into.

 

[chriscalandro]

I can get my panel and entire airplane down to only the HDX and D10. The HDX is by far the brightest. I have been playing with the autodim settings for the last 3 or 4 months but have never been happy with as dim as it got me so I put in the dimmer.

Do you have 2 displays?

 

[djones]

Chris,
How old is your HDX? Serial number? I have now heard this a couple of times and will try to get to the bottom of it.
Shoot me an email to support@dynonavionics.com with the info. I have a theory I want to pursue.

 

[chriscalandro]

The left display was just replaced due to a issue with the touch function, the right side is the original from the installation in May. The replacement and the old one don’t seem to have different behaviors, I’m happy to help any way I can to get this resolved.

the Everglades are very dark and that 1-2% is the difference between seeing upcoming clouds and weather and not.

 

[XPRSAV8R]

Just a note of caution, it's not wise to configure dimmed settings only while on the ground. Your battery puts out ~12.8v. However, your alternator puts out ~14v while in flight. I've had to adjust and readjust my settings after multiple flights. Even then, retarding the throttle on long descents can affect the alternator output which changes the voltage and possibly the dimming of the displays.

That said, I've also noticed a difference in voltage and brightness in my 2 display configuration at very low, dimmed voltages. In fact, my right screen will go black before my left screen.

@Dynon, is there a serial range that this problem was reported for?

 

[chriscalandro]

I actually built a custom LED controller that fits into a Dynon button panel hole. I’m using a PWM with a low pass filter to drive the dimming function off an AVR, regulated at 5v, so the variation isn’t a factor for me.

I’ve used the push button on the encoder to toggle between no duty cycle and full duty cycle (0v / 5v). It works really well, minus the Dynon side issues.

 

[scrollF4]

Well I have the same problem as Chris. Can't get my two HDX screens dim enough, and went to Dynon's manual dimmer with no success. I called Dynon Tech Support and told them my numbers from the Brightness Setup, and they said this should be good:
Brightness Source: External
External Brightness Voltage 14.4v
Brightness Target 100%
100% Brightness Voltage 12V
75% Brightness Voltage 7V
50% Brightness Voltage 4V
25% Brightness Voltage 1.5V
Min Brightness Voltage 0.1V

I bought these two 10" HDX screens last summer 2020, so they aren't old.

Don Jones, you mention a possible solution in your post above. I'll email you with a photo of my Brightness Setup screen. I've GOT to get these screens dimmer for night flying (particularly night IFR). It's making night flight quite difficult.

Scroll

SID MAYEUX
RV-7A

 

[chriscalandro]

Well I have the same problem as Chris. Can't get my two HDX screens dim enough, and went to Dynon's manual dimmer with no success. I called Dynon Tech Support and told them my numbers from the Brightness Setup, and they said this should be good:
Brightness Source: External
External Brightness Voltage 14.4v
Brightness Target 100%
100% Brightness Voltage 12V
75% Brightness Voltage 7V
50% Brightness Voltage 4V
25% Brightness Voltage 1.5V
Min Brightness Voltage 0.1V

I bought these two 10" HDX screens last summer 2020, so they aren't old.

Don Jones, you mention a possible solution in your post above. I'll email you with a photo of my Brightness Setup screen. I've GOT to get these screens dimmer for night flying (particularly night IFR). It's making night flight quite difficult.

Scroll

SID MAYEUX
RV-7A

I’ve been working with Don on this and I think we believe it’s a software bug with 2 HDX networked together.
If you turn 1 display off does the other dim all the way? And the other way around?

hopefully Don can chime in but the bug was repeatable and I believe they are going to be talking about what’s needed to fix it.

Personally I think someone added when they should have rounded when doing the brightness target calculation.

 

[scrollF4]

I copy all, Chris. They said they're looking at it, and I can expect a reply soon.

 

[djones]

Here is an update.....
It is actually a hardware issue. We are getting light leaking into the light sensor from the button board back lights. I did lots of testing on a 2 screen system and had one screen that would not go below 19% Brightness Target when the other would go to .2%. I did a bit of a farmer mod to the one that wouldn't go as dim and now both go to .2%. When you have one screen that say 20% is as low as it will go, when networked with another screen neither will go below the 20% value as software doesn't let any screen dim below the level of the brightest screen.
It is in the hands of engineering to come up with a final fix, but I should have a solution available soon, along with a plan to make it as painless as possible. Trust me when I say that if they go down to .2% they are dark enough

 

[scrollF4]

Here is an update.....
It is actually a hardware issue. We are getting light leaking into the light sensor from the button board back lights. I did lots of testing on a 2 screen system and had one screen that would not go below 19% Brightness Target when the other would go to .2%. I did a bit of a farmer mod to the one that wouldn't go as dim and now both go to .2%. When you have one screen that say 20% is as low as it will go, when networked with another screen neither will go below the 20% value as software doesn't let any screen dim below the level of the brightest screen.
It is in the hands of engineering to come up with a final fix, but I should have a solution available soon, along with a plan to make it as painless as possible. Trust me when I say that if they go down to .2% they are dark enough

Thanks, Don.
To be sure we're talking apples and apples, are you describing the dimming with the MANUAL dimmer? That's my setup: I wasn't aware the light sensor still had an effect when MANUAL dimming is selected.

 

[chriscalandro]

Don, is there a way we can remove the sensor influence when using an external control? That would easily solve the problem for me.

Also I’m not 100% sure but I think I see a difference in behavior if I turn the display on with internal battery before I hit ship power. Changing the minimum target way above the minimum value I see doesn’t seem to result in a brightness that goes to minimums.

I’m looking to get down to .5. I agree the .2 is too dim, would also be nice to have a minimum brightness target in addition to the minimum brightness sensor value.

 

[djones]

Actually, yes the light sensor is still active even with the external dimmer. I suspect we will look at changing that behavior, but no promises
yet.

 

[Raymo]

Actually, yes the light sensor is still active even with the external dimmer. I suspect we will look at changing that behavior, but no promises
yet.

Better yet, an option to honor the light sensor, or not.

 

[sven.jerlhagen]

I have a HDX1100 which does not dim in a dependable way. In order to make it dim enough I have increased the minimum brightness sensor value to 250. The sensor value is around 250 when it is dark. I believe I have the light leakage issue mentioned above. Any update on what to do about it ?

 

[djones]

Update: It takes a hardware mod to fix this issue, contact support@dynonavionics.com to set up a RMA to get the screen back for repair.

 

[chriscalandro]

Update: Got my displays back from Dynon and all is well. My displays now dim as expected. This has been a concern since last years installation and I'm glad to have it resolved.

Thanks!

 

[bruceh]

I just installed the manual dimmer knob and have tried to get it to work as I would expect. The Brightness menu has it set to external and moving the knob does make the screen (10" touch and a 10" classic SV display) go dim and bright.
The issue is the dim is way too dim and by barely moving the dimmer knob it goes from there to way too bright in about a micron. I have played around with the various voltage settings to no end and it has no gradualness to the dimming curve. About 0.25V would be good for night flying, and it goes from 0.1V to 0.4V on the dimmer knob with the slightest movement. It is either way too dim, or way too bright.
If I change the Brightness setting to internal, and use the buttons to INC or DEC the dimming it works as you would expect. Very easy to adjust the brightness to your liking with just a couple of stabs at the buttons +/-.

This $90 knob is worthless if you can't get a nice gradual increase or decrease by turning it.

Anyone else having this issue? Do I really need to pull both screens and have a hardware fix done, or is that just for HDX?

 

[Rhino]

Something is not right. You should have 0 to 36 volts on the dimmer, not less than one volt. How did you connect it? It should NOT be connected to pin 26.