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  #1  
Old 08-24-2019, 10:32 PM
JDA_BTR JDA_BTR is offline
 
Join Date: Dec 2013
Location: Baton Rouge, LA
Posts: 821
Default EngineBridge Integrated into G3X

I bought the latest EngineBridge to monitor my two PMAGs. Wired it up (power/ground, one channel for each PMAG). In this config it was pretty easy to use the WIFI network broadcast by the EngineBridge to monitor and change PMAG settings.

Learned while troubleshooting intermittent right PMAG indications to the EngineBridge that my right PMAG has a slight tendency to fail the mag sensor check on startup and flash yellow on its LED. Turns out if it starts in this condition it will run just fine, but it won't send data on its serial line until it is powered down and restarted without the mag sensor check failure. At least I think that's true. If I spin the prop a little the flash yellow LED on the PMAG doesn't come up on power-up; so I work around it a bit. I never knew I had this going on until I installed the EngineBridge.

Subsequently brought two analog outputs from the EngineBridge to the GEA24. Each output is a 0-5V signal corresponding to 18-48 degrees of PMAG advance. I used the Pos6/7 ports on the GEA24 J243, making sure to ground the ground pins for each port in the process. I did this by solder shrinking a shield ground onto the GEA24 side of the wire, and then solder shrinking to that ground two leads for pins at the GEA24; so I had two signal and two ground wires to connect, with a shield ground I screwed to the back shell. At the EngineBridge side I only connected the two outputs to the two conductors of the shielded cable, leaving the shield to float on that end. I could probably have added two wires into the shield ground solder shrink to make the ground pins but I had already made up a cable with the shield ground done prior to realizing about the ground pins. The way I did it worked better for the fittings I had on hand too.

In G3X config mode, I selected Pos6 and Pos7 as "custom" analog inputs, and in the calibration put 0 for 18 deg and 5 for 48 deg. I have my advance limited to less than 29.4, so I made the gage range 18-29.4 and that is the band displayed in the gage. I used the slider in the EngineBridge app to calibrate 0 and 5, since a 0 on the EngineBridge was really 0.005 at the GEA24, and a 5 on the EngineBridge was approx 4.985 at the GEA 24. But these actual numbers for the 18 and 48 deg advance analog voltages will vary on ground quality, length of wire, wire quality, etc.

What I got for my work is a left and right gage that shows the R/L PMAG Advance from 18-29.4, and it seems to read pretty accurately. It will swing in practice because the PMAG seems to not stay fixed on one thing and moves between two settings a lot even when everything in the plane and engine is very stable.

One thing I noticed in flight with this is that when I'm cruising at low altitude the advance might be 21 or so. Then when I pull back power to slow for landing the advance goes up to 25 because it is sensing the lower MP. I don't think this is avoidable given the way it works. Not sure it is a desirable feature or if it doesn't matter; but it is definitely there and no way around it.
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  #2  
Old 08-25-2019, 10:45 AM
Waiex-guy Waiex-guy is offline
 
Join Date: Oct 2012
Location: Rocky Point, NY
Posts: 25
Default

Excellent write-up. Thanks for the effort and detail.

Gordon
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  #3  
Old 08-26-2019, 02:26 AM
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Erimo Erimo is offline
 
Join Date: Jul 2015
Location: Marcoussis, France
Posts: 110
Default EngineBridge

Thanks for your feedback.
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