Scott Hersha

Scott Hersha

Well Known Member
I have a couple G3X install questions maybe somebody can help me with. I have one mag and one Light Speed plasma III. I don't have the UMA mag sensor I need to provide magneto RPM and for now only using the LSE for indication. So far, that isn't providing anything either - I get no RPM indication at all. I had a Dynon FlightDek 180 before and both systems provided indication without a sensor. My LSE is connected to pin 8 (GEA24) with the shield grounded at the backshell. The Garmin manual says I may need a 10K resister connected for Lightspeed ignition lead. Anyone know if that is a requirement or why I get no indication from that lead when it worked before?

One other question: My magnetometer failed the magnetic interference test with the tail strobe on. I have AerLeds with the Suntail on my rudder bottom. I've disconnected the lead for the strobe going to the tail and it passes. No interference with just NAV light, or normal NAV/strobe elsewhere, but with the tail strobe during the test oscillates between a fairly low number to over 400 during the flash. The shielded wire going to the tail strobe/NAV light passes along the upper longeron about 8 inches from the GMU22, which is mounted on a bracket in the aft fuselage spanning the upper longerons back near the bulkhead half way to the tail section. The shielded 3 conductor wire for the light fixture is grounded on both ends, as called out in the AeroLed installation instructions. The lights work great and put out absolutely no noise in my headset, but apparently have a strong magnetic field around the wire. Does anybody know if moving the lead down along the bottom of the aft fuselage will make any difference? It would be maybe 18-24 inches away if I did that. Any suggestions? I don't want to drag my old carcass back in the tail again if I don't have to.

Thanks. I know somebody will have an idea/advise on these issues.
 
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Scott,

Just passing along my G3X experience: one, an advantage of the mag sensor is that you will always have an RPM indication, even when you turn the mag off on an engine run-up. I don't have an answer for you on the LSE ignition hookup, but I'm pretty sure you will lose your RPM indication when you turn off your E.I. on run-up. The mag sensor has worked very well so far.

Two, I had a failure on my magnetometer check as well. I think it was the nav light in the tail. I went out and flew and if I turn the nav lights off and on, it doesn't have any discernible effect on the heading indication. I'm not sure if moving your wire will help, but I would fly first to see if it's a factor before subjecting myself to another round of torture in the tail. :)
 
Thanks Pat. I think the RPM indication (lack of) is probably installation error. I'll find out in a couple hours when I get to the hangar. Probably using the wrong pin and not setup properly. I didn't get the slick tach sensor (yet) because I didn't know I needed it. It wasn't necessary before (Dynon) to show mag rpm.

I'll try flying it with the tail strobe on and off to see what difference it makes in heading. The install/setup says a pass is important because it directly affects attitude and heading. Not sure what it has to do with attitude, but I'll see if the G3xperts have an idea how this should be addressed.

Thanks for the response.
 
I have your answer!

Scott Hersha said:
I have a couple G3X install questions maybe somebody can help me with. I have one mag and one Light Speed plasma III. I don't have the UMA mag sensor I need to provide magneto RPM and for now only using the LSE for indication. So far, that isn't providing anything either - I get no RPM indication at all. I had a Dynon FlightDek 180 before and both systems provided indication without a sensor. My LSE is connected to pin 8 (GEA24) with the shield grounded at the backshell. The Garmin manual says I may need a 10K resister connected for Lightspeed ignition lead. Anyone know if that is a requirement or why I get no indication from that lead when it worked before?
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I have your answer! Just 2 weeks ago I spent a ton of time trying to get the indication to work. Talked to Garmin and they solved it right away. The LightSpeed does not take it's tack signal low enough during the low to trigger the G3X. So by wiring a resistor to ground, that is lowering the voltage on the line, allowing the G3X to see the high part of the pulse. Manual calls for a 10K resistor, that did not work for me (guess not pulling the voltage down enough). Tech support said to try between a 2K and 5K resistor, that one somewhere in that range would pull the low down enough, without pulling the high down too much. Snipped my 10k resistor out and attached some alligator clips to a 2K (so I could change it out if needed while the engine was running). Started it up and immediately got a tack signal. Then had to change it to 3 pulses per revolution so that it did not show me idling at 3000 RPM.

I originally only installed the Lightspeed as my only tach sensor. When doing a mag check, you do loose the RPM indication all together. I have ordered (but not yet installed) a mag tach sensor (~$100)
 
Thanks Bill! I was going to try that next. I happen to have a couple 10K resisters, but also found a 3.3K. I think I'll try the 3.3K first. Maybe stop in to radio shack tomorrow and get a pack of 2K's. I'll get one of them to work this weekend. Haven't decided about the tach sensor yet. I'm thinking it might have limited value. When I turn off the LSE during run up, the RPM drops, but stays smooth. I'm not sure having a magneto RPM value is important in this case. Loss of my LSE in flight would involve flying without RPM until I land. Not an emergency and I wouldn't be going far with an INOP ignition system.

Thanks
 
Scott Hersha said:
Thanks Bill! I was going to try that next. I happen to have a couple 10K resisters, but also found a 3.3K. I think I'll try the 3.3K first. Maybe stop in to radio shack tomorrow and get a pack of 2K's. I'll get one of them to work this weekend. Haven't decided about the tach sensor yet. I'm thinking it might have limited value. When I turn off the LSE during run up, the RPM drops, but stays smooth. I'm not sure having a magneto RPM value is important in this case. Loss of my LSE in flight would involve flying without RPM until I land. Not an emergency and I wouldn't be going far with an INOP ignition system.

Thanks
Click to expand...

Hello Scott,

We note in your first post that you have a GEA24 engine interface. You will notice that in both the Rev. L and newer Rev. M G3X Installation manuals we don't show any external components being used with the GEA24 - just the older GSU 73.

Can you tell us the model designation (A,A1,B,C) on the side of your Plasma III?

It is highly recommended to install the hall effect sensor on the magneto and be done with it. There is very little value in monitoring the LSE output when you have a magneto with the hall effect sensor. The hall effect sensor in the magneto outputs a signal anytime the magneto is turning, so you can turn off either ignition and still have a RPM reading when you use just the UMA hall effect sensor in your magneto.

Thanks,
Steve
 
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Sorry Scott

I had missed that you had then new engine interface, I have the GDU73, so it may be different.

I was not planning the mag sensor either, but after a few runups, I really did not like the lack of RPM indication while doing my mag check, so I ordered one. Not rushing to get it installed, but will the next time I have my panel open.
 
Steve,
G3X installation manual, Rev. L, page F-2, Figure F-2.1 show wiring details for the GEA24 and Light Speed Electronic ignition, with reference to NOTE 15 (previous page). This note, same as the one for the GSU73 - 'A 10K external resister may be required for Light Speed Engineering interfaces'.

I don't know the model designation on my Plasma III, and I'm away from home today. I'll check it tomorrow and get back to you. I've had it for about 5 1/2 years. I'll go to the Garmin site and see if I can find the new Rev. M.

I assume you are saying I shouldn't need an external resister? JT is having a similar issue with a new panel in a Rocket he is working on. The guys at Stein told him he would need a resister somewhere between 2 and 10K. Have to try one until you get one that works. I think that Rocket has a Jeff Rose ignition.

Thanks for you help. I just bought some 2K resisters today so I would have an array to pick from.

On my other issue with magnetic interference when testing the GSU22 relative to my tail strobe, Dean Wilkinson from AeroLed told me today via email that I can isolate the Suntail ground from the tail structure by running my grounds back to the source via the shield. I'll try this before re-routing the cable.
 
Steve,
I just downloaded Rev M. Wow!! An extra 200 pages! What have I been missing? Rev M just came out in march, so I hope not too much. The note referencing the resister is still there on the GEA24 Lycoming interface diagram. It isn't shown on the diagram in L or M, but the note is there so I assumed it would be connected the same as in the GSU73 if needed.

I didn't know the magneto sensor would still supply a signal with the mag off - it's different than what I had before - no sensor. That would be a good reason to have the UMA sensor. One not so good reason is the $100 cost for the sensor v.s. $.99 for 5 resistors. The other reason is what do I do when I ditch the old technology mag that requires frequent maintenance and get a second EI?
 
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Hello Scott,

Yes, we don't show or need any pull down resistors when using the LSE ignition connected to pin 8 on the GEA 24. We probably shouldn't have referred to that note on the GEA 24 page.

Since your Plasma III isn't working, there is a possibility it is a rare "A" model with an open collector output which is why we asked about your model. We just recently learned that some of these models exist. This would require a pull up.

Thanks,
Steve
 
"Pull up"? What is that? Why didn't I need that with my Dynon 180? Doesn't it just read a pulse?

If you think I need a 'pull up', please explain.
 
Thanks for the email Steve. I can be pretty bull-headed sometimes when I want to do things a certain way and it doesn't work out. I have finally seen the light (thanks to my sensible wife) and will order the mag sensor today.
 
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