hexacopter help

[Gtriafylos]

Hey guys, i have a home built Tarot 680 (hexacopter) with turnigy multistar 750kv motors and afro 30A escs, with naza v2 flight controller. there is something wrong, i cant seem to get it to fly correctly. i have exhausted all options that i currently know. the flight controller works perfectly fine, but the hex just wont fly. when i take off, it will tilt in various directions and flip, and crash. when i hold it up and control it in manual mode, it seems to be relatively stable. i dont know what to do. please help.
thanks

 

[Motopreserve]

You are going to need to provide more info and specifics.

You mention the Naza works perfectly, was it on on another vehicle????

When does the flip happen? Immediately or after a bit of flignt time?

Are you using the internal PDB?

 

[Gtriafylos]

Hey, thanks for replying.

The naza was on a blackout Mini h and it worked relatively good, put it on tarot 680, changed it to hexacopter mode, turned voltage protection off, set gains to approximately 120% and attempted to fly.

Regarding your second question, I would throttle up in manual mode, and as soon as legs would come off ground, it would become super unstable. I am 100% sure that the motors and props are correct way around, could I have faulty escs or motors?

And yes, of course I'm using internal PCB

This is for a school project and it is stressing me out so much! I'm generally great with this stuff.

Thanks

 

[jfro]

Start with Basics.
Motors connected in right order.
Props on properly, make sure labeling is up, not just the proper clockwise or counter clockwise.

Naza Assistant set up.

Double check that hex is set up
Go to radio / mounting and make sure you have the gps offset setting set up correctly. Double check everything.

Put X2 on a channel 6 knob. x3 on a channel 7 knob if you can.
Set you basic gains to 100 across the board for pitch, roll, yaw, & Vertical
In the drop down box set both pitch and roll to either your x2 or x3 and remember which knob you set up.
Leave yaw and vertical alone for now..
Set you atti to 80 for pitch and roll and assign it the other x2 or x3.

Check your switches when hooked up to the assistant and make sure your manual, atti, and gps switches are working as well as all your channels. Calibrate them as well.

Do the dance to calibrate outside with no metal around, which includes no cell phone or car keys in your pockets.

Take off in ATTI mode.
Take it up 8 -10 feet and then work on adjusting your gains and atti. MR should twitch a bit while hovering when you get to high. Back it off just a bit. Don't tune or fly in manual mode till you are stable in atti mode.

This should get you started.... I"m no guru, but this works for me.

Sorry if it's redundant.

 

[Motopreserve]

It could be intermittent ESCs or motors.

There have been reports of the intrrnal PDB being a little flaky. I never had an issue with the Naza, but I did have issues with my superX on that frame using the internal PDB. Seems the copper runs are not equal in length, and that can cause issues.

Have you tested the motors/ESCs on the bench in manual, to see that they are firing together and there are no inconsistencies? I'm assuming you've done the ESCs calibration?

 

[Gtriafylos]

hey,

jfro, i have done all of these things, multiple times and it doesnt seem to solve the problem, thank you for your input though, ill keep it in storage for a later date!


motopreserve, yes, i did the esc callibration, all with a large array of jumpers to do them all at once. i am going to get a tachometer to ensure that the motors are at the same rpm when CSC commands are executed and at various speeds to ensure that they are all in sync. i notice with on of my motors, it seems to shake quite a bit after a specific RPM, could that faulty motor have caused the problem?

also, i notice that sometimes, when in atti mode, and im holding it above my head, when testing to see if it responds to movement correctly, it sometimes, on its own goes from 50% to 80% throttle and doesnt stop. its really weird! because it works fine on the mini quad.

regarding the PDB, it is being used, and its a big help. many people have used this without any problem, are you sure it could be affecting it?

thanks

 

[Motopreserve]

No, I'm definitely not sure. But figured I'd let you know that it's worth keeping an eye on. They have been problematic - so just be aware that it's possible. Typically it manifests itself by making the ESCs unhappy. Probably not your issue here, but you never know.

If one motor is acting differently, that's definitely a problem. The shaking could be caused by bad bearings in that motor - and is certainly worth checking out. You can check for irregular sound with your ear close - as well as checking for any play in the shaft. You may need to open it up to really inspect the bearings.

If you are holding the MR above your head to test it - always have it in manual mode. The atti mode can be confusing for tests when it try's to correct itself.

 

[Gtriafylos]

i have come to the conclusion that the problem is with my escs. Afro 30A escs work on 1000Hz refresh rate, and the naza v2 outputs 400Hz

probably gonna buy a new set of escs, anyone care to comment before i do so?
thanks

 

[Motopreserve]

id be surprised if that was your issue. Have you found people that have run into a problem with the AFRO/naza combo?

The refresh rate has been a weird marketing deal for a bit - there are no systems, as far as I know, that take advantage of anything beyond 400hz. So despite ESCs that are touting higher rates, it's not being utilized anyway.

 

[econfly]

1000Hz is either meaningless or the problem.

Standard PWM signals are little pulses ranging from 1 to 2 milliseconds in width. So the fastest you can send the signal is at a period of 2ms with a tiny gap between pulses. That means 1 / 0.002 s = 500Hz is the fastest you can send PWM signals, and for practical purposes 400Hz is the top end you see in most ESCs. Here is a one minute video I made a while back on how PWM signaling works:

So, if the Afros really do operate at 1000Hz they are doing something non-standard. However, I bet this is just meaningless marketing and not the actual problem.

 

[Motopreserve]

That's what I was thinking (marketing), but it is odd they would be listed as so high, no? I have seen 600hz (KDE???), but never higher than that. And was pretty sure that the rest of the system wouldn't accept any advantage above 400hz (or I guess 500hz?) anyway.

Regardless, econfly knows his sh*t, listen to him

 

[econfly]

Thanks Moto!

How about a quick video of this thing flying or taking off and a few pics of the build? We may be able to see something obvious that could help. Like Moto says, the ESCs are probably not the problem, but you never know...

 

[Motopreserve]

One thing I wondered about was whether or not the issue might be caused by the ESCs having inconsistent firmware. I recall a while back someone having similar issues - later to find out that 3 of 4 ESCs had one firmware, the last having a different firmware.

Something like that could be as simple as a couple coming from one batch (or period of time) and others from a bit later - but sitting on the shelf together. Order comes in - no way of knowing which firmware you're shipping...

 

[Gtriafylos]

sorry for late reply,
went out and bought the new escs, did what i had to do to get em running, and the multi rotor takes off just fine. roll, throttle and pitch work great, but yaw immediately induces roll and pitch, ultimately resolving to nothing but difficulty and well, a crash. do you think that my zippy 30C lipo isn't discharging enough power to run the motors?


link to battery:
https://www.hobbyking.com/hobbyking...Flightmax_8000mAh_4S1P_30C_AU_Warehouse_.html

link to motor http://www.hobbyking.com/hobbyking/..._3525_750Kv_14Pole_Multi_Rotor_Outrunner.html

i have another battery, should i put em in parallel and see if that fixes the problem?
thanks

 

[Gtriafylos]

i have been studying for my specialist and method test! year 12 aint easy haha!

ok another question and somewhat unrelated, its my 18th birthday soon, and, well, i want an oscilloscope. what should i be looking at? 500 seems a good price.

thank again!

 

[Motopreserve]

Unfortunately there is no data on that motor at the product page (at least I couldn't find it on my phone), so I'm not sure exactly how much amp draw you'd be experiencing.

But I do not believe that a mismatch of battery to motor draw would only create issues on Yaw movement. And 30C is not particularly low - especially at 8A. That gives you a discharge rate of 240A.

What's the radio you are using? If Yaw stick movement causes roll/pitch movement, it sounds like there could be curves/mixes in there or something???

 

[Gtriafylos]

I'm using the taranis x9d and looking at the channel monitor, yaw changes only changes yaw channel. I'm using the x8r SBUS port to send info, and when I click on naza, I choose DBUS as its the only option that works.

 

[Motopreserve]

Yep, sounds like radio is all setup correctly based on checking the channel monitor. It was just a thought.

Are the props balanced and the motors level?

 

[Gtriafylos]

Yep, they are, could unbalanced props really cause the problem?

 

[Motopreserve]

I don't think unbalanced props would cause the issues you are having, but it's always good to get things straight, if only to rule them out as a contributing factor. Motors being un-level could probably cause some issues like this, but I'm not even sure.

Sorry, I'm out of ideas for things to check...

Hopefully someone will chime in here with some ideas.