Hi,
I had a crash this week with my tarot T960 and can't figure out what happened and need you help with theories?
What happened was that my lipoalarm sounded at 3.7V and I went back for landing (I was only 10m from my landingspot).
- I went back in Loiter mode.
When I was 3m away and 3m over ground my hexa started to spinn in a oscillating way and dropped hight and hit the ground. Broke my landing skid and some propps...
My ESCs seams fine and all motors are spinning correctly.
One thing I have in mine is that maybe my compass calibration wasn't done correctly? When I did it it said it was fine but I remember that it had only a few measuringpoints one spot.
Could a bad compass calibration caused this crash?
I haven't been able to retrieve the telemetry logg from this flight. The only file I can find from this flight is a .bin file, which I can't get any info from. Maybe you guys are more lucky?
I've uploaded it to dropbox: https://dl.dropboxusercontent.com/u/10888145/2014-07-16%2018-52-30.bin
Spec:
Pixhawk with the newest firmware
Frame: T960
Motors: Tmotor 4014 400kv
ESC: ZTW 40A OPTO SimonK flashed
Battery: 6s 8000mah
Power: Via powermodule (home made for 6s with 5v Bec) and power from separate Bec to servorail
5.8ghz fpv equipment (far away from my GPS)
I would really appreciate some help here!
Take care!
Replies
Hi.
The provided log is the only log that matters, Telemetry logs are no good for trying to find a cause.
Unfortunatly, your log ends too soon. Pixhawk that stops logging is something we've seen before, - try a different microSD card - that worked for me.
All I can say, is that already at liftoff, your cell voltage drops from 4v (fully charged) to 3,53 v , this is very, very bad - most likely - you have a bad battery pack, with huge internal resistance, or one or more defective cells in it.
This - and the description of the crash, does point toward too little power, giving PID's that are completely wrong, and crash was the "expected" outcome.
Thank you Andre!
I did a post in the facebook group for Pixhawk/APM and one guy there said that the current went so low that it made the Pixhawk restart. Maybe thats why the telemetry log is interrupted?
Btw, If the voltage dropped from 4v to 3.53v, wouldn't the lipolarm sound then? It was set to 3.7v!
I guess that lipo I used is garbage now... Tanks a lot for you help!
Please note that a standalone LiPo alarm is connected to balancing connector (no voltage drop with load)
Your actual ESC voltage is what's left after voltage drop in cables ,connectors, PDB, and the current sensing shunt.
You may think that (unless you calibrated your voltage-sensing), the measured voltage might be very wrong, in which case the voltage could be different from the logged one, but still - the voltage drop at liftoff seems unusually high.
Aaah, now i'm with you!
Could something else cause this except a bad Lipo? ex bad esc or my home made power module?
too tiny power wires, bad solderings, or partially broken wires (where many of the small threads are broken off near soldering) would result in higher voltage drop than normal, giving such results.