External Dimmer Question

[Dynon101]

I installed an external dimmer potentiometer using PIN 25 and it works however the dimming function seems to be "choppy" meaning that the display brightness goes up and down in large steps and not very smooth,

I fiddled around with the voltages of the various steps however I cannot seem to get it right.

If someone has a 12 VDC airplane and has smoothed out their remote dimmer feature can you please let me know what values you used in the various fields of the external dimmer setup?

THANKS!!!

 

[dynonsupport]

Are you using the default voltage curve in SkyView for an external dimmer, or did you adjust it? Is your potentiometer 0-5V, 0-12V, or ???
Is it a linear pot or a log/audio taper?

 

[CGameProgrammer]

I think this is how it's meant to work...? At least that's how it works for me. You define the volts for 25%, 50%, and 75% brightness, so you just get those exact brightness amounts and not a smooth interpolation.

 

[dynonsupport]

It should smoothly interpolate between those values.

 

[CGameProgrammer]

Well mine doesn't. My potentiometer is about 12V at the 'full' setting, smoothly varying to 0V at minimum, but the HDX display only has 5 possible brightness settings when using it. It does not interpolate. I don't really care because I always have it either at full brightness or minimum brightness and nowhere inbetween, but for what it's worth it does not interpolate.

I configured the display to be, if I remember right, 75% at 9V, 50% at 6V, and 25% at 3V. When I dim the pot the display remains at full brightness until the pot is <= 9V at which point it reduces to 75% brightness until the pot is <= 6V at which point it immediately switches to 50% brightness, etc.

 

[Dynon101]

thanks for the feedback. I have a 0 - 12 volt potentiometer and ithe swiped has a smooth linear change from zero to 12 VDC.

I have since fiddled with the values and therefore do not remember what the default values were so I cannot return to original.

When the values were default it did not dim smoothly and seemed as CGameProgrammer points out to be choppy...about five steps so that is why I fiddled with the values.

QUESTIONS

Can you please tell me what settings you recommend to make the transition smoother?

Can I use the power supplied by the EMS PINS as the power supply for the potentiometer instead of a source from ships power?

Thanks

 

[dynonsupport]

I just tried this on a 15.1 system. The values are linearly interpolated between points. It doesn't only change at the points you have defined.

A few things that might make it feel that way though:

1) It samples at 1Hz, so it only updates the brightness once a second. Move the knob too fast and it will feel like it's stepping.

2) Human perception of brightness is not linear. You need to quadruple the brightness to perceive a doubling. So going from 50% to 100% isn't that noticeable. You probably want your curve to represent a logarithm if you want the knob to feel linear in perceived brightness.

Attached is a video showing that the brightness is interpolated.

If you are looking for a power source that is backed up, then the 8V out to the GPS is most appropriate, which is on pin 29. The 5V out from the EMS could also work.

 

[CGameProgrammer]

You're right, I tested it today and the HDX is correctly linearly interpolating the brightness values; it was just the once-per-second refresh that threw me off.