I set up dual batteries yesterday and did some test flying, got two 5 minute flights in with no payload on the same batteries. Was stoked, but wanted to go back today to test with a 5lb payload. Running QC 3328 motors, APC 14x4.7 Slowfly props (for testing), two 4S 8000's and the 5lb dumbbell. I had just done a full update and changed most settings in MK tool using this tutorial: https://vimeo.com/43066036 Not sure if I had done something wrong or what, the GPS was working great and it seemed to be flying better than ever. Heres what happened... First Flight: Took off in manual, switched to GPS and she was super steady considering the wind. Took her around for a bit, really feeling good! However, about 2.5 minutes in, the copter just dropped down from about 6 feet (was hovering low luckily!). If you are looking at the ass of it, it leaned right and booms 6/7/8 when into the dirt. Luckily no damage just needed to readjust motors and landing gear. I checked my new cable to run the dual batteries, it was a little hot (Using 14AWG wire), so I switched back to one battery thinking that the dually might have been the problem. Decided to switch on the iPhone on for the next flights, good idea! Video of flights: Second Flight: Took off in GPS mode, running just the single battery. Flew nicely for about 30 seconds, then as you can see in the video, it did the same thing again. I noticed (after impact) that motors 6 and 7 both were stopped, while the others kept spinning. After the copter settles, motors 6 and 7 want to power on again and spin. Third Flight: Ok, maybe its something with the GPS (since I was just fiddling with it earlier). Took off in manual, got about 10 seconds and bam. Same thing. Motors 6 and 7 seem to be powered off and then try to power on once its settled. Decided to call it a day after that! Other facts: 1) Did not have an SD card since I left them at home, so no GPX. Will put one in there next time...but hopefully the video can help shed light on the situation. 2) Could the 5lb payload have been too much for the APC props? I was flying yesterday with no issues at all, however no payload. I wonder if the stress of the 5lb dumbbell made the motors fail briefly. 3) The copter suffered a crash over a month ago, and booms 6/7/8 were damaged, wondering if the motors got messed up too. Going to put some replacement motors on 1,6,7, and 8 tonight and try again tomorrow. In the meantime, any help would be appreciated! Need to solve this problem ASAP!
I did a compass calibration not too long ago, and she was flying just fine until the failure. Another thought, I zip tied the dumbbell to the bottom of the frame of the copter, could the payload's center of gravity have caused it?
It'd be interesting to know your BL temperatures, as the first thought I had was that the BLs (the brushless controllers) for the 2 or 3 motors on that side might have overheated and shut off. There's little other explanation in my mind. If you shut off the GPS and it still did it, then it has nothing to do with the GPS. And the dual batteries also are unlikely to do with anything. But you said you ran 14 gauge wire to the LiPos...that's a little thin, but I doubt that's significant, either. I really think there's an issue with your BLs.
I will check the temps tomorrow, is that something I do in MK tool? I know when I went into the OSD mode today to check GPS/Altitude Hold switches, the motor temps ranged from 29-32 Celsius, compared to the tutorial that had 26-29 Celsius, both at idle. I wondered if that was a little warm...
Also forget to mention, no errors in MK Tool. I checked immediately after the first crash and nothing, ran a scope and everything seemed in order.
Ok so I did a motor test, motors cut off and stop if I get up to around 175 on the throttle for a period of time (about a minute). BL Temps are : 37,40,39,39, 39,34,35,38. Definitely looking like this may be the source of the problem. Solutions?
Here's what the scope looks like, you can see at 0:18 the motors cut off and gas drop, then it tries to cut back on a moment after. I have a spare BL board, should I just go ahead and try to swap them out and see if that works?
Are those motor temps bench only right? I would say it be much higher flying with that payload. I with Steve here that its a BL over temp and cut off problem. But in saying you get up to 175 throttle it could be a EMI problem. I had something similar where i couldnt even get my heli to take off in some areas. My solution turn your compass effect to zero and "ignore magnet error at startup" but if you not flying with gps/navi you can disconnect them and try.
Yes these are bench temps, no payload. I'm sure it was higher while flying, but they seem to cut off almost right away (same as when I was flying with payload today). What do you mean by EMI problem? I have already had some compass errors before, I wonder if this is a lingering issue... :/
EMI from battery wires not twisted to long, motor wires to twisted. buzzer placement the list goes on!! The highest Interfering Magnetic field is generated by: Buzzer, Motors, Power Cables and Metal Parts (in approx. this order). If problems with the MK3Mag are only noticable at higher throttle, it is likely that the interfering magnetic field is generated by power lines. Ideally the individual DC-lines should have very few bends and Plus/Minus should be routed parallel as their magnetic fields are then compensated by each other
So you are saying the wires may be causing problems? All motors and wiring are the same as they've ever been, however I added an FPV camera and cable today, could that be causing an interference? I wrapped excess cable from that around the frame. Seems so minuscule, but that sounds like what you a talking about.
Yes wires placement can cause it. If you add that fpv set-up take it off and see if makes a difference. You might need to re-route the wires make them shorter and if you put a transmitter close to something with the same frequency it could cause interference with your rx/tx at higher rpms
Removed all FPV stuff and its still cutting power to the motors. I'll have it a 175 on the throttle and it cuts off every 5 seconds or so. Stays off, then powers back up. Is there some setting I might have mistakenly hit in MK? I also noticed in my Channels, that Channel 5 randomly goes from 0-245, and I can't find the source. One moment is 0, the next its maxed to 245. Tried to disable but it still does that...
Omg lol what I would do is start over make a new model in your tx and assign all your poti to correct switches. Load mk tools double check everything flick all the switches making sure nothing random happens and go from there.
It's not heat with those numbers. And I doubt it's EMI either. Maybe it's current limiting? What does your current graph look like? Or it could be marginal motor bullets. That did this to me once.
Alex: If you remove the props and run up the motors to simulate "flying" do you still see the same effect? If so, can you post a GPX file. The hope is that that GPX file will give additional diagnostic data. Also, using MKTOOL you can copy GPX files from the microSD card without ever having to remove it from the NC board -- to avoid the situation that you have a crash and don't get a GPX file. Andy.
Hello Alex, What transmitter are your using to control the kopter? The intermittent status on Ch.5 is concerning. Is the transmitter set to "Acro" and not "Heli" Greetings, Adam
I am using the Graupner MX20. I seemed to have gotten the intermittent Ch.5 thing fixed, but it has not solved the problem of my motors cutting off. Trying to get an SD card formatted to put into the Navi, hopefully that will tell us more. Whats strange is that the motors seem to be a little more reliable when I am testing them with the TX. It's only during Motor Tests that they constantly fail, when they are pushed a little more.
Are you testing the motors with props on or off? And this is a 4S system with BL 2.0, right? Are you testing with a bench supply or a LiPo?