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Power board problem


After several intensive days with no issue, I suddently had a problem with power to some board. The ROV would not arm unless I ticked off the pre-arm check. After this I got problems with the sensors, depth, gyro and compass. Does anyone know what the problem could be and how to fix it?

(Jacob) #2

Can you post a telemetry log where the vehicle is reporting the issues? The log files are found in Documents/QGroundControl/Telemetry, you should turn on the ‘log while disarmed’ option in the general settings section.


How do I upload these? tlog is not allowed in attachment

(Jacob) #4

I just updated the forum settings, please try again.


My file is too big… 5991 kbit

(Jacob) #6

It will help me if the log is as short as possible while still demonstrating the issue. However, if it is not convenient for you to produce a log like this, I have just upped the max attachment size as well :).


The ROV is not connected now,2017-12-04 15-36-46.tlog (5.9 MB)
so I am trying to upload the last tlog.


I am sorry for the big file, if this one does not help, I will try to make a short file later. Thanks for trying to help me.


Hi Jacob,

Did you have a chance to look at the log file?

(Jacob) #10

This appears to be an issue with the power module. Here is a plot of the voltage measured at the power module port, and at the servo rail where the ESCs connect. Both values should be a steady ~5V. The pixhawk is reading more than 6.5V on the power supply, this is why you had the warning when you attempted to arm.

It looks like something is failing with the power module causing the reference voltage to be incorrect, then the power module fails completely or disconnects, and the pixhawk is now powered by the servo rail with the correct reference voltage.

What I recommend you do now:

  • Unplug the connector that is plugged into the ‘Power’ port on the Pixhawk.
  • Power on the ROV, and get a short telemetry log while the Pixhawk is not connected to the power module to verify that the Pixhawk is functioning correctly.
  • Measure the voltages on the power module connector that you unplugged to verify the issue. Here is the pinout:
  • Contact support@bluerobotics.com for replacements.


The two 5v wires from the power module has been disconnected the last >200 dives with no issue, so I don’t understand this. I will try to measure as you describe though.

(Jacob) #12

Well this is an interesting piece of information.

Can you tell me why/how you disconnected them? Is there any possibility that they could have made electrical contact after being disconnected?


I installed a relay after the power module since that seemed easyer than sourcing the round connecters found before the power module. I then discovered that the power module powered the Pixhawk, thus I pulled out the two wires. I will check if they somehow make trouble now. Sorry for hacking the ROV…