Help me understand the HDX dimming operation!

[mwtucker]

I have been researching the dimming operation of the Skyview HDX system and I keep finding differing opinions on how it works. Dynon has told me different things... Does anybody really know how the dimming circuits work? For example, I have a two-display system. Is it possible (without using an external dimmer knob device) to connect the two displays in such a manner that one display can control the brightness of both displays? Dynon's first answer was to connect the DIM OUT pin from one display to the DIM IN pin on the other display and that allows either display to control the brightness of both displays. As an electrical engineer knowing about the open-collector circuit and pulse-width modulation (PWM), I couldn't see how that would work. Dynon later said that only the display whose DIM OUT pin was connected could control the brightness of both displays (i.e. a master/slave topology). I have read in forums that the SV-INTERCOM-2S has no backlight (but a DIM IN pin). I have also read that the SV-INTERCOM-2S does have a fixed intensity backlight. I am totally confused. Can someone with knowledge about this please explain what a Dynon system can and can't do (dimming wise)? I have not found any clear wiring diagrams.

Thanks!
Mike

 

[tniel7331]

SkyView System Installation Guide – Revision AM 4-19
DIM INPUT (Pin 25) The backlight level on a SkyView display can be increased or decreased using a varying DC voltage of 0 to 36 volts DC, such as provided by the Dynon Avionics SVKNOB-DIMMER – see Accessory Installation and Configuration, SV-KNOB-DIMMER for details. See Display Setup, External Brightness Management later in this section to configure brightness levels for specific voltages. DIM OUTPUT (Pin 26) The DIM OUTPUT signal is an approx. 120 Hz (may change in future Software revisions) Pulse Width Modulation (PWM) signal directly proportional to the screen brightness – 100% to 0.02%. This output is designed to directly control the dim level of devices such as LEDs; a common use is for the back-lighting of switches in a panel so that they dim at night in conjunction with SkyView’s automatic dim levels.
The DIM OUTPUT (Pin 26) signal is an open collector to ground - it acts as a switch to ground, and does not source any power itself. Pin 26 can sink a maximum current of 120mA and a maximum voltage of 40V. The DIM OUTPUT signal is not analog and cannot be used to control the dim level of devices that expect 0-5V, 0-12V, or a resistance as their dimming input. Do not connect the DIM OUTPUT (Pin 26) signal from multiple SkyView screens in parallel. The DIM OUTPUT signals from each display is not synchronous, and this will lead to inconsistent

 

[mwtucker]

SkyView System Installation Guide – Revision AM 4-19
DIM INPUT (Pin 25) The backlight level on a SkyView display can be increased or decreased using a varying DC voltage of 0 to 36 volts DC, such as provided by the Dynon Avionics SVKNOB-DIMMER – see Accessory Installation and Configuration, SV-KNOB-DIMMER for details. See Display Setup, External Brightness Management later in this section to configure brightness levels for specific voltages. DIM OUTPUT (Pin 26) The DIM OUTPUT signal is an approx. 120 Hz (may change in future Software revisions) Pulse Width Modulation (PWM) signal directly proportional to the screen brightness – 100% to 0.02%. This output is designed to directly control the dim level of devices such as LEDs; a common use is for the back-lighting of switches in a panel so that they dim at night in conjunction with SkyView’s automatic dim levels.
The DIM OUTPUT (Pin 26) signal is an open collector to ground - it acts as a switch to ground, and does not source any power itself. Pin 26 can sink a maximum current of 120mA and a maximum voltage of 40V. The DIM OUTPUT signal is not analog and cannot be used to control the dim level of devices that expect 0-5V, 0-12V, or a resistance as their dimming input. Do not connect the DIM OUTPUT (Pin 26) signal from multiple SkyView screens in parallel. The DIM OUTPUT signals from each display is not synchronous, and this will lead to inconsistent

Thanks tniel7331. I found out today from Dynon that the Skyview Network controls dimming across (all?) the Dynon devices that connect to the network. I couldn't find that anywhere in the documentation (I have missed a good bit, though because of the amount of info in those documents!) That makes sense because the only Dynon device I see with a DIM IN input is the SV-INTERCOM-2S.

 

[Rhino]

The intercom backlight is not fixed. Pin 5 is used to dim it just like DIM INPUT on pin 25 of a Skyview.

 

[mwtucker]

The intercom backlight is not fixed. Pin 5 is used to dim it just like DIM INPUT on pin 25 of a Skyview.

I have read on forums that the only thing that dims is the POWER/TX LED. Since I have not yet powered up my system, I am not sure if there is a backlight for the legends on the SV-INTERCOM-2S.

 

[Rhino]

That's all the manual mentions, so apparently I was mistaken. Sorry. I assume they don't dim the backlight because it's not a screen or indicator they think could be too bright.

 

[mwtucker]

I spoke with Dynon tech support this afternoon and learned some good things...

1. The SV-INTERCOM-2S does not have a backlight--only the POWER/TX LED dims.
2. The Dynon Network transmits brightness settings to all network devices. Those that have backlighting will be dimmed.
3. You can adjust the brightness of either screen (in a two-screen install) and the brightness of all network-connected devices will follow.
4. You can dim external (i.e. non-Dynon) devices by connecting their dim circuit to either DIM OUT pin on the displays.

 

[Rhino]

4 is only true if the external devices accept a PWM signal for dimming. Some stuff still looks for a variable voltage for dimming.

 

[mwtucker]

4 is only true if the external devices accept a PWM signal for dimming. Some stuff still looks for a variable voltage for dimming.

I agree with you on this. Thanks.