I’ve been running my new rover using Pixhawk, 3DR radio, and uBlox + Compass on top of a Exceed RC Mad Torque for about a week now and finally have it fairly well tuned. After driving around for about 36 minutes this morning via Droid Planner I had something odd happen…midway between waypoints the truck stopped and although it was a long ways away and hard to hear it sounded like the Pixhawk bootup sounds. DroidPlanner never indicated that it disconnected but almost immediately said it was in initializing mode. I was able to immediately set back to auto mode and set it to the next waypoint (defaulted back to #1) and away it went. Approximatly 1 minute later it did the same thing. Each time this happened home was reset to the point where it appeard to reboot.
The only change between this set of waypoints and the previous 20 minutes worth was that I had set a delay before moving to the next waypoint although I hadn’t yet reached the waypoint with this set. I brought it back to me again using DroidPlanner, checked connections and reloaded a new set of waypoints this time without a delay at any waypoints. Again shortly into the trip the same thing happened. I cleared and loaded a new waypoint to bring it back then proceeded to run for another 19 minutes with no further glitches.
Battery voltage was fine the entire time and ended at ~7.6V, per the logs it looks like the lowest it ever dipped was 7.1V and that was not during the run, I verified this voltage with a multi-meter. Each reboot started a new log however DroidPlanner never indicated that it disconnected. Each new log seems to show a very brief period without GPS.
I’m using the rover to prepare to build a quad and a shutdown like this could have been catastrophic had I been in the air, but what I’m trying to figure out is if this is a hardware problem or possibly a Rover firmware problem.
Has anyone experienced a similar problem? Any ideas where to look to determine what could have caused the issue?
I was wondering that myself but I’m not quite convinced of that for a few reasons, for one I thought that the power module that comes with the Pixhawk was supposed to prevent that. In addition the log doesn’t seem to show anything although it may not have been able to write that to the log. Since the rover was driving across a baseball diamond under very little load I don’t believe it was a load issue causing the brownout.
I also drove for an additional 19 minutes with no problems and stopped because I ran out of time, not because of low voltage on the 6 cell NiMH pack.
How are you powering the steering servo? If it’s drawing on the Power Module, that could be your problem.
Do you have the BEC wire from the ESC on the servo rail? It should be fine to power the servo from that. At the same time, that should actualy provide a back-up power supply to the Pixhawk. It can switch from the servo rail, to the PM on the fly. But only if the servo rail is less than 5.7V.
Personally, I don’t recommend people use the PM on 2S battery supply. It’s a little bit low. The dropout voltage on that regulator 1.1V, and the output voltage is set at 5.3V. That means that the minimum voltage input is 6.4V. It is conceivable to get spikes this low when operating around 7V.
The battery is connected to the PM which connects to the Pixhawk via the 6 pin power port and also passes through to the ESC/BEC that came with the Mad Torque. The servo cable from the ESC/BEC including the power pin is connected to servo port 3 on the Pixhawk, so as I understood it and as you seem to indicate this results in redundant connections for power.
Also this is a single servo steering and each time it happend the truck was already turned to the next waypoint and was headed straight so the servo should have been drawing very little.
I’m not sure if this has anything to do with it, or if it is how things are supposed to work but this is what happens when I power on for the first time:
Plug battery into PM
Pixhawk boots and gives the everything is working tones
Arm the pixhawk
ESC/BEC gives its tones that would normally have sounded on first power on and signal from RX
Pixhawk appears to reboot as it produces the tones again like it had been powered on
From that point everything works as anticipated. I can disarm the pixhawk and re-arm it without the ESC or Pixhawk reboot tones. However if I power off the ESC with its remote switch the pixhawk stays on (which tells me the PM 6 pin cable is working) and if I then turn on the ESC again the Pixhawk reboots. Is this normal?
Should I power the Pixhawk from my 3S Lipo via the PM and connect the NiMH 6 cell directly to the ESC then out to the servo ports?
I’m going to head out right now and do some tests with the waypoint hold times to see if I can cause the problem to repeat.