Hi,
I had recently swapped out my APM 2.5 with a new Pixhawk on a DJI 550 that is pretty stock (DJI motors, esc). I had successfully tuned it and had flown it several times without problems. I added a camera to it using a servo to trigger the camera. I was testing the function by manually triggering the camera. The camera was set to my channel 7 into the Pixhawk and then using RC10 to move the servo. Everything seemed to work fine, I had triggered the camera several times in loiter mode then all of the sudden all motors stopped and it dropped from the sky. I looked at the logs and didn’t see anything immediately that would indicate why this happened. I would be greatly appreciative if someone with a bit more knowledge might be able to help me out with the log. I really want to know why it decided to do this all of the sudden. Thanks in advance for any help.
Hi Cstallings,
After looking at your log, it seems you lost connection with your transmittor, as all RCIN dropped to zero at line 13249 around the time (just before) you switched to Stabilize at 13275…
Usually this could happening if you forget to throttle up after switching from Loiter to Stabilize, but this was not the case…
I guess that you didn’t have FS_THR_ENABLE enabled, which would have initiated an RTL in this case…
See line 64 FS-Throttle enable = 0 (not active)
I also see that you don’t have a failsafe on your battery see FS-BATT-ENABLE at line 42, which means at low battery no RTL, but just drop out of the sky…
Hope your drone survived the drop…
Good luck,
Erik
Thanks Eric,
I unfortunately did not set up my fail safes before doing my testing. The Hex did survive with minimal damage which has been repaired. I have a theory what I did wrong. I think I may have created a brownout on the system based on how I wired the servo for the camera I added. The receiver is powered by the PPM encoder thus being powered by the autopilot’s 5v. I had placed a regular servo wire on channel 7 and brought that into channel 8 on the pixwawk and then plugged the servo into AUX10 which I now suspect was pretty stupid thing to do. I am guessing this was way to much power and triggering the servo eventually caused the brownout? I noticed that I was able to move the servo about 5 times normally but the drop at 13275 appeared to correlate to triggering the servo again. I have since installed a separate BEC for power and am now only using signal from the pixhawk and receiver. That way the servo has its own independent power source. I’ve bench tested it and it appears to work. I have not tried to fly it yet however. If I indeed caused a brownout like I believe will it cause any permanent damage to the autopilot system? Also based on how I have it wired now do you believe that this is the correct way to do it? Again I greatly appreciate you taking the time to look at the logs and help me out with this.
Thanks
Thanks Erik,
I think I may have solved the issue but I’m not 100%. I may have created a brownout situation the way I was powering the servo. I was using power from the receiver which was in turn powered by the ppm encoder. I think that when I used the servo it eventually caused a brown out. I have since installed a separate BEC for the servo power and the servo works however I have not flight tested it. Unfortunately I got a bit ahead of myself and didn’t set up the fail safes before I tested the servo. fortunately the damage was very minimal. If you don’t mind, I would be greatly appreciative to hear your thoughts on this. Does this sound like a plausible explanation?
Thanks
Hi,
Ok had a look at CURR (vcc component) which is your PIXHAWK 5v, around the 13249 area.
If you right click the Value Graph area there is a option to show point value’s which makes it easier to find the line number in the graph, to correlate to an eventual drop in power…
By doing this everything on the power side seems to be fine (no drop under 5v), so you didn’t lose PIXHAWK control.
But connecting a SERVO Wire from PPM input channel 7 to the PIXHAWK output channels 8 doesn’t sound correct to me. ( I guess you are trying to get output from PIXHAWK mixed with input from your Receiver to generate a SUM Signal which has receiver content, and PIXHAWK content…) and send that back to the PIXHAWK by using the PPM sum…
Your PPM out goes to the PIXHAWK PPM input (SUM signal) and that should be the only link between PPM decoder and your PIXHAWK.
If you want to control a real SERVO from the PIXHAWK output channels (AUX 10) you will need to use an external BEC to feed the powerrail of the PIXHAWK independent from the 5v which feed the flightcontroller itself.
So I think you may have caused this by drawing more current from the PIXHAWK output channels at the time of the switch, and by doing that dropped all output’s (Motor Output as well) to zero…
Even a Failsafe would not have saved your Copter in this case…
Why not using your Channel 7 on the transmitter, to Pass through the PPM into the Pixhawk and onwards to the output channel 7 and use that to control the servo?
I am doing something similar with my Channel 6 -> Pass through to control the position of a Gimbal Pitch value…, works like a champ…, and no need for extra wiring.
See Gimbal Setup in MP, and the activation of Pass Through options…
Remember that you will need to pre-arm the PIXHAWK with the safety switch before it is passing through the signals to your camera (Took some time for me to figure that one out…)
Baed on the fact that testing this new approach (external BEC) seems to work, tells me that you didn’t create permanent damage to the PIXHAWK controller…
Hope this helps…
Hi FpvDrone-EG,
I think you are absolutely right. I’m about 90% that’s exactly what happened. I have it set up correctly now with a second external BEC that I am using to draw power from and am only receiving signal from the PIXHAWK to control the servo. I’ve tested it without any problems. Not sure what I was thinking the first time, I think I was just getting ahead of myself and wanted to see the camera trigger. Thanks for everyones help.