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Keep smoking GPS modules

Thebigskysky

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Location
Kennewick, WA
I have a Flywoo Explorer LR with the GPS and like may others I was frustrated with the time it took to acquire sufficient sat lock after plugging in my battery (3-5 minutes). So following a video from TMac (link below) I wanted to isolate power to the module so that it can acquire its lock quickly without the EMF noise which in TMac's testing significantly reduced cold lock (down to 30sec) and once it was locked, the rest of the drone can be plugged in and be ready for flight. This is accomplished by pulling power off the balance lead of the battery, stepping it down with a 5V BEC, and powering the module directly with that while the TX/RX wires are still connected to the FC. Below is my most recent attempt...

-Beitian BN-220 GPS
-iFlight 3-6S Micro 5V BEC

The Explorer runs a Flywoo Goku F411 V2.1 FC and the GPS utilizes UART 2 (TX2/RX2) on the board. The GPS module is first connect to my PC and allowed to get a sat lock while I change a few minor settings in U-Center as well as download the U-Blox AssistNow Offline information to the flash memory to further aid in fast acquisition. Once everything is tested and checks out, all my solders are triple checked, voltages are checked, everything is good, I placed the GPS module into the drone and plugged in the isolated power. GPS module lights up like normal and picks up a fix rather fast (warm start), at this point I plug in the XT30 into the quad and the GPS module LEDs flash a few times and then go dark. The unit is dead, confirmed through the PC.

I start my autopsy:
-BEC Voltage: 5.06V (cant replicate a spike no matter what I try)
-TX/RX voltages: 3.15V (again, cant replicate a spike no matter what I try)
-Nothing is shorted, everything is good.

What are the possible causes of this? I contacted TMac and he responded rather fast however he could only offer that maybe the Beitian units aren't good for this (somehow) and suggested i use the Matek SAM-M8Q module with Matek Micro BEC's as that is what he has used with no trouble. I'm just at a loss as to what could be spiking the module or causing the damage, am I missing something really obvious that I should feel dumb for?
I have a few dead GPS modules at this point as I initially figured i wired something wrong, then the second time I DID wire something wrong (checked brand of GPS so for some reason the positive/negative are opposite on the other brand, didnt notice), but this time I was very through and ensured good clean solders, i even siliconed the connection after (rest of my board has a conformal coating I added), and metered out all the wires prior to plugging in the GPS. Everything should be right on paper so I know if I am missing something, its super obvious and I should be publicly shamed for missing it.

Thank you for your time and help in this matter!

 

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My guess would be that when you connect the XT30 the + makes contact before ground, and the current temporarily finds a path to ground through the tx/rx lines to the ground on the GPS module and fries stuff on the way.
 
My guess would be that when you connect the XT30 the + makes contact before ground, and the current temporarily finds a path to ground through the tx/rx lines to the ground on the GPS module and fries stuff on the way.
Would you suppose of a way to fix this? Or a way around it?
 

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