Rotax 914 TCU Warning and Caution Lights

[JohnH]

I am installing an SV with a Rotax 914, and I would like to have the TCU warning and Caution lights on the Skyview instead of separate lights on the panel.
From what I read, it seem that the contact function in the EMS on any available GP input should do the trick.
What I don't understand is how to hook it up. The Rotax diagram shows 2 wires for each lamp with a 12V output to illuminate the lamp. The Rotax Installation manual clearly says not to hook the negative wire to ground anywhere.
Will this work if I only hook up the 12V output to a GP input to funtion as a contact?

 

[dynonsupport]

Tricky.... If the TCU has two wires coming out and both are supposed to go to a lamp, there's no way to know which has the switched power on it unless this is specified explicitly. Plus, if he switch is between 12V and open, then SkyView will see it as the same level, as open is 5V to SkyView, and 12V is open to Skyview as well. In this case, you'd need a pull-down resistor to make it work.

 

[JohnH]

Thanks for the information. I will do some more research on the Rotax side and try to find out which one of the wires is switched.
Failing this, perhaps I will just put in the normal lamps.
It would be nice to have a nicely integrated system with the same warnings and alarms for all the systems on the aircraft.

 

[JohnH]

Is it possible to have a simple schematic to see how the contact input should be wired. I am struggling a little to get my head around this (call me dumb).

If I find out which wire is switched, perhaps I can make it work with a resistor between the 2 wires, but it seems that this may not be reliable as it will not necessarily be the same ground shared with the Skyview.

Another thought I have had is to wire a small relay into the warning lights and then use the relay as a contact for the Skyview?

 

[dynonsupport]

It's not obvious from the installation documentation (we looked) if the + terminal is switched, or the ground, or other, and the actual wiring that will work depends on the answer to that. We have an email out to try to find out what's going on there. You might give your Rotax support channels a call to see what you can come up with. We'll post back here when we hear back.

 

[JohnH]

I have sent the forum discussion to our local Rotax distributor. I will wait to see if they can come up with an answer.

I have had no joy on the Rotax engine forums yet.

 

[JohnH]

Feedback from the Rotax distributors here and the factory. They say the ground wire is switched with the positive remaining static with 12V or whatever the TCU voltage is at the time.

 

[dynonsupport]

In that case, you just need to hook the EMS' wire to the TCU's switched ground with no external components needed. All the needed resistors and such are already inside the SkyView.

 

[JohnH]

Great, hope this helps someone else hoping to do the same thing.
Thanks.