Hi All,

This is my third crash (repeating the 'exact' same scenario deliberately) in the past two days. I have found the core problem of the issue -> Using camera (RPi camera module) on-board the flight wipes out GPS signal 'entirely'.

Here is my setup:

  1. Autopilot board: 3DR's APM 2.5, with ublox GPS module, 3DR Telemetry EU (900 MHz), RC Txm/ Rx (Flysky) Spread spectrum/Freq.hop ?
  2. Networking harware (with WiFi): Raspberry PI + camera module + Edimax WiFi dongle.
  3. The two boards are NOT interfaced with each other. I am jsut powering up RPi from one of the ESC's BECs 5V.
  4. I just made a shielding for this problem. Improves but with uncertainty (more on this later).

As far as I could see, I could (luckily) not find interference on 2.4 GHz of Txm/Rx and the WiFi (802.11 b/g/n) that I was initially expecting.

But to my surprise, what happens is as soon as I start shooting the video, the 'satcount' goes to 0 for about a few seconds and then starts getting back to normal. Originally I have satcount of 9.. drops quickly to 0 as soon as I start the video shoot and then slowly increases to 7 until video footage is completed.

When the satcount reduces, copter goes CRAZY (yes, literally crazy), 'does not land' but flies away to some remote corner and crashes before I could take back control (Log attached shows the glitch clearly). I cross checked that this happens only in LOITER mode when taking the video; Loiter uses the GPS. Shouldn't it land, when copter loses GPS fix (for 5 seconds)??

I did ground tests without flying, just commanding the video to start, brings down satcount to 0, as seen in Mission Planner.

I used Aluminium shielding, it helps quite a bit, but may make copter drift during flight video unreliably. The cause may also be the camera + camera cable.

I wonder how can this be possible in the first place. uBlox GPS uses 1.575GHz carrier wave and such a popular RPi camera module should come with ISA interference certificate/clearances, I am completely bamboozled!!! Another post issuing similar problem but with HK camera here

Below is my latest setup, still some glitches in satellite count, but yet not the perfect solution. Glitches in satcount is 1 to 3 during video shoot. Did anyone faced this? Looking for a neat solution.

Any suggestions are welcome. 


   

Thanks and regards,
Shyam

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This problem was indicated and solution patented (patent US 6522291 B1) "GPS receiver sharing an antenna ground plane with an EMI shield"

I thing that a DIY drones community using a cheap GPS equipment/modules not take it into account. Patented solution is that shield, possibly can be DIY.

This paper Article Link shpes a solution to, but this in a strange language. Pictures are readable.

Details Below:


Shyam Balasubramanian said:

So, slowly this problem is coming to light.

...... I am saying this as people have not deliberated on this issue too deeply (from the scientific literature I have read till date) 

If I may, I'm going to expand on post a year or so ago :-)

GPS signals reach the earth surface at extremely low levels, in fact so low that they are under the average rf noise level.

Clever mathmatical trickery allows your receiver to extract valid code from this "noise"

But to do this, the signal from the actual antenna, the little brown ceramic block, is highly amplified.

And this is where the problem comes in.

Most digital electronics generate rf "noise", and this noise gets into the sensitive amplifier, after the antenna, and a lot of your cheaper devices, like cameras, have a lot of digital noise.

And it does not even have to be in the same frequency range of gps signals, to completely swamp the amplifier.

Effectively making it "deaf" for the gps signal.

The only option is to get the gps as far away as possible, from other digital circuits on your aircraft.

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