D37 Pin 26 Dimmer - does it work?

[Mark P.]

I'm using the external dimmer module and I have both HDX screen connected to it and it works great to dim the screens.

In the HDX D37 harness, pin 26 is the Dim Output white wire. I have the Ray Allen trim indicator and the Garmin 175 GPS connected to the D37 Pin 26 white wire but the external dim control has no affect on the brightness of anything I connect to it.

Am I misunderstanding the purpose of Pin 26? Maybe I need to connect the Ray Allen trim and Garmin to the Violet wire of the Dynon dimmer module?

Any help?

Thanks

EDIT: I also wanted to add that the comm panel, knob panel, and AP panel do not dim. Are they suppose to?

 

[John Bright]

You don't need the Ray Allen trim indicator because Skyview shows trim position if you have the EMS module.

SkyView (except the SE version) and GPS 175 have auto dimming. If auto dimming works well you don't need a separate dimmer knob. Have you tried the auto dimming feature?

GPS 175 wants a variable voltage input from what they call the lighting bus if you want external dimming. Search for "lighting bus" in the install manual. The way I read it, you can connect SV-Knob-Dimmer violet wire to the GPS 175 lighting bus input. Do read the install manual about setting parameters for the lighting bus.

The Ray allen trim indicator dimming function is either on or off, full or dim, no in-between. They don't make it easy to find this info but Mr Google found it: "ray allen trim indicator dimmer". Give the white wire nothing and it is full brightness, give it 12V and it is dim. You could connect it to the nav light switch so it's dim when nav lights are on. But really you can remove this indicator because SkyView has it on the engine monitor screen.

The SkyView install manual says SkyView controls dimming of panel modules over the network so yours should dim.

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The dimmer output from SkyView is a PWM square square wave sink to ground. As the SkyView install manual puts it:

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.​

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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.​

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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 behavior.​

 

[Mark P.]

I know I don't need the Ray Allen trim indicator, but I installed it because it's old school and I like it LOL. This airplane is WW2 themed so I sort of liked the old looking LED indicator. They had full glass panels back in WW2, right??

I'll have to figure out why the comm and other panels are not dimming with the Dynon. They are all connected via the hub and I don't think there is anything else I need to wire to have them dim. It could just be a setting somewhere...

 

[maartenversteeg]

Note that the signal from the external dimmer know is clearly an analog voltage, which can't drive any current, this goes to the dim input on the Dynon display pin 25. Then there is the DIMMEr out put pin 26 that is referred above, this is a pulse width modulated signal with an open collector output that can sink upto 120 mA, so this can be used either to dim a lamp directly if the needed current is less then 120 mA. If more lamps need to be dimmed then a amplier may be needed to provide the needed sink current. This output signal though may not be suitable for other avionics boxes to be used as a dim input. AS said this is a pulse width modulated signal, not an analog output voltage. If the external avionics box expects a voltage then this is not the proper signal. This signal really is intended to dim external control lights for which a pulse width control is the propoer way to reduce current through the light