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G3X TOGA SPST Diode orientation?

Jesse

Well Known Member
Those that read the title should know what I mean. Which way do the diodes orient?
 
I've never used any diodes, are you tieing a 650 to a SPST toga as well?
Even though I think Garmin said it was ok to tie the 2 together I still use a DPST pushbutton for the toga to keep them isolated.
If you still want to use diodes the anode would go to the unit (G3X/650) and the cathode to the switch, other side of sw goes to grd.
 
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Hello Walt,

When connecting a TO/GA pushbutton to the G3X system and to a GTN navigator, the two discrete inputs in question must not be connected together. Otherwise, the operation of the flight director could be affected if the GTN is powered off. That is why figure 26-1.7 of the current G3X installation manual (rev AB) shows a DPST switch, and specifically states "do not use a single pole switch".

The G3X installation manual does not show any diodes involved with the connection of the TO/GA pushbutton.

- Matt
 
Thanks for setting the record straight Matt.


Below is the old thread that talked about tying these togther, I knew I'd seen this come up before:


g3xpert

06-26-2014, 01:40 PM

Steve,
I know we talked about this in a separate email, but has the Garmin team concluded that both the G3X and 650 TOGA lines can be tied together using a spst switch?

Hi Bill,

As we discussed, we have been using a simple SPST button in our G3X show displays for the TO/GA button wired to input discretes on the GEA24 or GSU73, and GTN 6XX/7XX for some time with no problems.

We studied the electrical design of these inputs and decided that it was fine to tie these pulled-up input discretes together and use a SPST button switch to ground instead of the DPDT that isolates the two input discretes.

Thanks,
Steve
 
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Hi Walt,

My bad. It is best to provide good isolation between the GEA and GTN inputs so neither can affect the other. This is why it is shown this way in the installation manual.

Thanks,
Steve
 
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Referencing that old thread, I have done numerous installations with the SPST switch with excellent results including my own RV8. I have incorporated the DP switch the last 4 installations only because I try to comply with Garmin recommendations, and Stein sells a really nice one!
 
The reason I ask is that I am using a stick grip button for TOGA. There was a reference to using diodes, but I couldn't find the details about orientation. I'll use Walt's recommendation.
 
We have switched long ago to a DP switch (for several reasons) for the TO/GA function switch. It fits in the same hole and has a nice positive click to it. Can't say we've ever used any diodes in that installation....

Cheers,
Stein
 
Coming up on this TO/GA wiring question now.
I will use the DPST switch (harder to find) for GTN & GEA TO/GA connection.
I believe the diode (pull-up resistor?) reference is in the install manual when you choose to use one of the GP discrete terminals (GP 1-5) instead of one of the four discrete IN terminals.
Is this correct?
If I use GEA Discrete 1-4 terminals, then I may just connect the TO/GA DPST switch to one of those. (Pins 40-43)

REF: G3X IM (AF) Fig. 30-2.2
 
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