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Garmin G3x Experts

rvator10

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:confused::confused:Garmin G3x Experts
Engine Analyzer connector J244 pins 44 MASTER CAUTION & 45 MASTER WARNING, can you please help explain the differences between these two pins.
I have provisioned for one red light on the panel and wanted to use it for say something as simple as ? low oil pressure?.
And is it as simple as connecting it to pin 50, 12V out?
thanks
 
Hello Rvator,

One consequence of having such a voluminous installation manual is that it can occasionally be difficult to find the right information, but we are here to help. :) Here are the relevant passages that describes the master caution and warning outputs from the GEA 24:

15.3.9 Discrete Outputs

The GEA 24 has 2 annunciator outputs, these outputs do not require any configuration and can be optionally wired to an external annunciator. Discrete Out 1 acts as a master warning annunciator and is active any time a warning CAS message (Red Alert) is displayed on the PFD. Discrete Out 2 acts as a master caution annunciator and is active any time a caution CAS message (Yellow Alert) is displayed on the PFD. Reference Appendix E for wiring guidance.

DISCRETE OUT 1 is "master warning" - goes low when a red (warning) CAS alert is active.

DISCRETE OUT 2 is "master caution" - goes low when a yellow (caution) CAS alert is active.

The two states of these outputs are as follows:

INACTIVE: Floating (can be pulled up to externally sourced Vout in the range 0 ≤ Vout ≤ 33 VDC). Leakage current in the INACTIVE state is typically ≤ 10 uA to ground

ACTIVE: Vout ≤ 0.5 VDC with ≤ 20 mA sink current. Sink current must be externally limited to 20 mA max

18.3.2.21 Annunciator Outputs

The GEA 24 and GSU 73 have two discrete output pins, which can be used to drive external indicator lamps. These outputs are optional and do not require any configuration.

DISCRETE OUT 1 acts as a Master Warning annunciator, and is active (pulled low) any time a warning-level (red) alert is displayed on the PFD.

DISCRETE OUT 2 acts as a Master Caution annunciator, and is active (pulled low) any time a caution-level (yellow) alert is displayed on the PFD.

See Figure E-2.2 and Figure E-3.2 for guidance on wiring indicator lamps to the annunciator output pins.

What this tells us is that the Master Caution output pin (J244, pin 45) will be pulled to ground any time a "yellow" CAS message is visible on the PFD display, and the Master Warning output pin (J244, pin 44) will be pulled to ground whenever a "red" CAS message is visible.

Figure E-2.2 shows how to wire a light bulb or LED indicator to the Master Caution and Master Warning pins. You want to connect one side of the bulb to the GEA 24 pin, and the other side to your 12V aircraft bus. If using LEDs, the anode connects to 12V power and the cathode connects to the GEA 24. Also, be sure not to use the 12V transducer power output from the GEA 24 to power your lights... these are intended only for engine sensors, not light bulbs.

Hope that helps, let us know if you have any further questions.

- Matt
 
The way I understand J244/44 and J244/45 is that if you get a master warning or alert they pull low.
Meaning if you have your oil pressure setting for a red or warning below some number, when your oil pressure goes below that number you will get a red warning on the PFD. When the warnng shows it will ground pin J244/44.
This will also happen with any other warning. Say low fuel pressure/ redline rpm or anything you have setup to give a warning. Same goes for J244/ 45 but that will light with a yellow alert.
I find that the annunciator on the PDF is enough.
So to wire the warning light, you would wire 12v to the light and the ground to pin 44 or 45. When the PFD shows a warning it will ground the pin to complete the circuit.
 
I had a customer that used one light so I wired pins 44 and 45 together (diode isolated) so a red or yellow message would trigger the light. The only problem is, unlike in larger aircraft where the Master Warning and Caution lights reset, the discrete is pulled low for the duration of the message.
 
I had a customer that used one light so I wired pins 44 and 45 together (diode isolated) so a red or yellow message would trigger the light. The only problem is, unlike in larger aircraft where the Master Warning and Caution lights reset, the discrete is pulled low for the duration of the message.

The pilot should be able to cancel a Master Caution (yellow) but not a Master Warning (red).
 
I disagree, Walt.

The Master Caution & Warning is designed to get your attention. Once you know of the problem, you reset it, and it is there waiting for your next major problem (if you're having a bad day). If you leave it illuminated, you could potentially miss a more serious issue.
 
If using LEDs, the anode connects to 12V power and the cathode connects to the GEA 24.

Hope that helps, let us know if you have any further questions.

- Matt

Matt,

Just to clarify: you need a current limiting resistor between the led and power, right? Connecting it directly will make it shine very bright only once, and never again... Or is there a limiter inside the internal circuit?

Thanks

Hermann
 
Just to clarify: you need a current limiting resistor between the led and power, right? Connecting it directly will make it shine very bright only once, and never again... Or is there a limiter inside the internal circuit?

Hermann - Correct, if you are using a plain LED (i.e. not a "12V LED" annunciator with a built in resistor) you must provide your own resistor to suit. The GEA 24 does not provide any current limiting, it just switches a pin to ground for your convenience.

Another thing to point out, related to some of the other posts in this thread... the Master Caution/Warning annunciator outputs are tied to the CAS (Crew Alerting System) messages on the PFD display. When a new caution or warning CAS message appears in-flight, it will flash until the pilot acknowledges it by pressing the Enter key or changing to the Engine Page (if the caution/warning message was caused by an engine parameter). Once acknowledged, a CAS message will remain on the PFD without flashing. Similarly, the Master Caution/Warning outputs will flash when a new CAS alert is posted, and will remain on steadily after the message is acknowledged. Hope that clears things up.

- Matt
 
I disagree, Walt.

The Master Caution & Warning is designed to get your attention. Once you know of the problem, you reset it, and it is there waiting for your next major problem (if you're having a bad day). If you leave it illuminated, you could potentially miss a more serious issue.

You're right, however I believe some systems won't reset unless the fault is first cleared.
 
<SNIP>
Asking a question that might have been answered above but isn't quite clear to me;

Is it possible to have a "Master Warning" and a "Master Caution" push-to-cancel switch that illuminates when triggered by an associated CAS message?

I realize the EFIS CAS message will remain until the condition no longer remains, but I'd like to simply have the alert annunciated by an illuminated switch that can be extinguished with a push.

Push.jpg

EDIT: Just found this very recent thread indicating this feature is not currently available but will be in the future, hopefully.
 
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