Hello all,
I have been working on a VTOL modification for a couple of weeks now, and had just gotten to the point of conducting a few hover tests. The night before I went through and checked to make sure everything was properly functioning, and all was well. On the day of the test however, I began running into issues. At first, the ESCs started giving the error beeping tones on two of the motors; however, after unplugging the ESC from the battery (Turnigy 5000 mAh 4 cell) and Pixhawk and reconnecting them, all was well. I then went to go run the flight test, and one motor began spinning with much higher thrust than the others. The day before I had checked these and the limits were configured. To resolve this I simply reconfigured the limits. Now we get to the interesting part. After these issues were resolved one of my ESCs stopped sending power through the BEC, and would not emit any startup tones in the motors. I attempted to reprogram it with the use of a program card, also to check to see if it was sending signal to the motors, which it was not. This started with just one ESC, but has now affected a total of three. I can't seem to understand what the issue is. Any ideas or help would be greatly appreciated!
Replies
Im happy to help. Lots of good advice and support on this site and the others. I have learned everything from the wikis and the blogs.
Good luck moving forward!
Harry, ultimately I just ended up replacing the ESCs. I received information that these were poor ESCs from someone who had also tried them. I replaced the shot ESCs with 60a Turnigy Plush ESCs and have had much more success with it. Here recently I have done several successful tests with them. Also, I did apply several of your suggestions. I ended up making the ultimate battery parallel connector and ESC splitter and it works great. I also removed the BEC wires from all but three ESCs like you suggested. Thank you for all of your help!
Even, I just came upon a video in the wiki that may help address your issue. In the wiki, search for " ESC sync issues" If this is actually your issue, this will confirm it.
Harry,
These are all wonderful suggestions. I will certainly check out the batteries. That could be the cause of the issue. The multiple BECs could be flooding the board and have caused damage to the ESCs also. That is something I will fix.
Like you said with the ESC extensions, I did purchase a larger AWG wire for them because I wanted to minimize resistance. It never really dawned on me that the separate lengths could cause timing differences. It makes perfect sense though. If timing becomes and issue that will be the first place I look.
Thank you for all of your help! I will post an update once I make these changes!
A few items. from your diagram it looks like you have two batteries, not in parallel, but independently supplying power to two motor / ESC 's each. This could be causing trouble as the batteries are not equal. I have a parallel battery arrangement and the discharge is never equal, even when you might think it should be. In other conversations when others have had trouble initializing the ESC's it came up that a common ground is required for all the motors, from your diagram it looks like you have two separate grounds. Might work, Not proper.
My build also had extensions on the ESC wires. The advice I collected recommended that I oversize these wires and keep them the exact same length to avoid resistance from interfering with the timing.
Also important and easy, only use one set of BEC wires. DO NOT tie them together, or use different BEC wires for different tasks. This creates multiple grounds in the low voltage. You don't have to cut the wires, just don't use them.
IMHO I would try the following.
1. make sure the entire system uses only one BEC. Then try everything again.
2. change your battery setup to be wired in parallel so that you have one battery system and one ground.
3. I would not face the issue of equal length ESC wires until you've exhausted all other possibilities. Then, perhaps a bench test. In this case it may be best to test moving the ESC's out on the booms so the ESC wires can be really short. three feet is really long for ESC wires, I think pushing the limit.
To answer your question Harry, three of the ESCs ended up refusing to send power through the BEC. When this happened the ESCs stopped working altogether. I didn't remove all but one of the voltage wires from the ESCs in case it would affect the signal. A friend of mine said that I only need one similar to what you said. Unfortunately I'm unsure where the issue with the ESCs is stemming from. Below is just a rough diagram of my layout. I extended the motor wires to reach out to the motors on the motor booms. I wondered if this could have caused the issue. The lengths were 3 foot extension for the back motors and 2 foot extensions for the front. The frame is a Skywalker X8 with the ESCs & batteries in the front. The weight is probably close to 4.5 - 5 kg.
VTOL Diagram.jpg
Martin, the "jump start" seems to work for most, however, I have found that with a heavy lift beast anything fast during the maiden flight is terrifying. some manual tuning is needed prior to being airborne.
Evan, has 70A esc's so I figure he has a heavy beast...
"I have found that the initial spin up of the motors is not usually consistent. In other words all the motors don't have the same power level just before takeoff."
I agree. Maiden flights, I select an open turf field and "jump start" take-off with quick throttle-up. Rather than the slow "cautious" application of power which has a greater potential of the "flip over kiss of death".
I have found that the initial spin up of the motors is not usually consistent. In other words all the motors don't have the same power level just before takeoff. Prior to tuning a custom setup this effect is much worse and cause flipping.
It sounds like you reconfigured the motor limits for only one of the motors. Perhaps this is causing the flight controller to contribute to the problem.
On another issue, you stated, "one of my ESCs stopped sending power through the BEC." How meany ESC's are you useing the 5v supply. My understanding is that only one of the ESC's should use the 5v supply.