Building a hexacopter

[ladykate]

Sony nex 5 or EOS M. Some camera for FPV.


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Curiously, why Sony Nex 5? What advantages does it have over a GoPro (that you will take advantage of, of course). A medium length lens was my conclusion earlier - but that can be had with GoPro, too - and at a fraction of the weight. I'm trying to figure out if I want to go this route with my machine.

 

[extrememc]

I really want the raw capabilities. The jpegs that come from GP are not sharp enough. I have a EOS so I will probably go with it. My plan is to build first then fly for awhile before I add a $1000 underneath it. I am hoping that GP will release a camera with raw capabilities and save me some $$$.


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[extrememc]

Woah... lots of questions from everyone

OK - the terms AUW stand for All Up Weight. Basically if you get your hex and put it on the ground ready to take off so it's loaded with batteries, camera gimbal - everything you are going to fly with on it then put your hex on a set of scales that would be your AUW. It's a very important number because it is fundamental on how long you are going to get in the air, how many amps you are going to draw from your packs and how much strain you are going to put on your motors.
With any Hex you need to establish your AUW first. Then divide this number by 6 (or 8 if it's an octo). The resultant number will tell you how much thrust each motor has to produce to enable hover. However, nobody wants to just hover, we all like to fly around a bit and assuming you want your craft to hover at around mid stick you need to double these numbers and add 10-20% overhead.
eg; If your AUW for your craft was 3kg (3,000g) then your motors would need to produce 500g thrust each just to get airborne. In order to achieve meaningful flight you would need 6 motors that can achieve around 1.1kg (1,100g) of thrust each.
The amount of thrust a motor can achieve will be laid down by the manufacturer and will depend on voltage (3s or 4s pack etc) and prop length and pitch.
Too steep a pitch and you will draw too much current through the motor and it will overheat. Too little and the motor will need to spin faster and you will lose efficiency - all of the above effect your flight times.
A very good tool is eCalc -> http://www.ecalc.ch/xcoptercalc.php?ecalc&lang=en . It DOES have it's deficiencies but it will give you an idea of what combos work and what are way out of whack.

BEC stands for Battery Elimination Circuit. It's basically a regulator that will provide (in esc cases) a stabilised 5v supply. This can be fed to the flight controller and/or receiver but you should be mindful of how much current an esc bec can provide. If you over stretch them they will fail. I use the Naza M v2 with PMU. The PMU is in itself my bec so I use opto isolated esc's with no bec whatsoever.

@mediaguru - If you are going to use the 5v supply from one of your esc's the reason you should cut the other 5 positive leads off and only use one is because if you don't you will have 6 becs in circuit. Each bec will differ in voltage by a very small amount and you will have a conflict going on with all six in circuit - hope that makes sense. I AM NOT talking about cutting the wires that feed the motors here I am ONLY talking about the bec outputs.

@wkf9425 - Max flight time is such a variable because every component plays a part in a self build craft. However as a guide, my FY690s has an AUW of around 3.5kg and I get a comfortable 20 mins in calm conditions and around 18.5 mins in windy/gusty conditions. This pulls around 7,800mah from my packs so well within the 80% rule.
With regards to payload... the bigger the hex, the bigger the payload (generally). A criteria for my was portability so I didn't want to go huge. I also knew I was only going to be using a GoPro with this set-up so I designed the whole hex around theose sort of weights (including the Arris CM3000).
I favour T-Motors for motors and props - they are not the cheapest but they are VERY good quality and at the end of the day the only thing that is keeping your money aloft is the motors and the props !! :shock:

Hopefully that's answered your questions guys - anything else shout.

Thanks for the information. Definitely bookmarked!

After reading this I am starting to feel like getting a ARTF kit may not be best or am I taking this wrong. I am thinking that I need to be sure that the kit I am getting will carry the intended payload. Even if it says it will. Do the math anyways.


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[wkf94025]

Noob question of you Hex Jedi: assuming you are NAZA based, are you subject to all the same issues as those of us in Phantom land? J hook, TBE, descent speed limits, and now with v3.04 firmware, horizontal speed limits? Confess I have no concept as to what your flight controller's brain and its configurability are all about. Do you have a Assistant software similar/identical to that in Phantom land?

If you are stuck with all the limitations/flaws that Big Brother has inflicted on us in Phantom land, whatare the non-DJI options you considered, or perhaps chose?

 

[The Editor]

Noob question of you Hex Jedi: assuming you are NAZA based, are you subject to all the same issues as those of us in Phantom land? J hook, TBE, descent speed limits, and now with v3.04 firmware, horizontal speed limits? Confess I have no concept as to what your flight controller's brain and its configurability are all about. Do you have a Assistant software similar/identical to that in Phantom land?

If you are stuck with all the limitations/flaws that Big Brother has inflicted on us in Phantom land, whatare the non-DJI options you considered, or perhaps chose?

I am Naza based but do not suffer any of the TBE or J Hook problems simply because with a Naza M v2 the GPS puck and compass are combined in a single puck which you mount on a Carbon Fiber pole about 150mm up and out of the way of the rest of the craft. It's very easy to set a declination offset simply by rotating the puck the required number of degrees.

On the Naza v2 we are on firmware v4.02 and there are NO no-fly zones or any limits put on decent speed or anything else for that matter.
As an aside - A 700mm span hex is way, WAY more stable in decent and general flying than a Phantom which is a 300mm quad. It IS still possible to suffer VRS if you really brought it down quick but you get used the signs of unstable air and avoid it before it happens!
The Naza assist is pretty much like the Phantom 2 software in Naza mode really - Not an awful lot different.

I did consider the Wookong (but thought it was too pricy for what it was) and Arducopter APM 2.5. What I love about the Naza though is:
1) It's very easy to set-up
2) It has great connectivity via CANBUS
3) It has the ability to provide a feedback loop to the IMU's on the Zenmuse gimbals which give the camera stabilisation greater accuracy.

 

[wkf94025]

Thanks Editor. Good intel as always. Two follow-on questions:
1) so I assume you have no practical need to fly your bigger more expensive machine in Manual mode? (About to try Manual mode with my Phantom as a work-around on the 2m/sec descent speed limit);
2) I assume you do NOT have an easy way to do POI (circular pan around a point of interest) at this time? I believe some of the more expensive DJI flight controllers have that native?

Kelly

 

[The Editor]

Hi Kelly,

I come from a background of flying collective pitch R/C heli's for years so manual mode is no stranger to me. I HAVE flown it in manual mode just to see how she handles and also I have manual as an option on my TX just in case there should ever be a 'fly-away' moment - It seems the only documented way of forcing an errant Naza out of 'fly-away' is to flick the flight controller to manual for a few seconds and then back to Atti of GPS.

With regards to POI flying, again since I have been used to 3D heli flying I suppose muscle memory has helped me there - I have done years of flying nose in, tail in, inverted etc. You just have to put enough stick time in until it becomes second nature to you. If you have to think about it, it's too late! :lol:
When you fly 3D it all starts off in a normal world.... Left is left, right is right, up is up and down is down
As soon as you go nose in Left becomes right, Right becomes left, up is still up and down is still down
Flip it upside down and left is right, right is left, up is down and down is up
Things get really interested when you go inverted nose in... then Left is left, right is right up is down and down is up.
Now, the thing I haven't mentioned in all of that is yaw !! That inverts and becomes opposite rotation upside down !!!!

Like I say.... If you have to think about any of that while you are flying then it's way too late. Sometimes brain freeze kicks in on even the best pilots !!

If you take a look here there is some 3d flight showing stick movements! -> https://www.youtube.com/watch?v=it0C1TXEzck In comparison multirotors fly themselves!

I suppose what I'm getting at is if you put in enough stick time then flying quads/hex's is really simple and you can concentrate more on getting the shot you want (which is what I enjoy) more than the actual flying as this becomes second nature to you.
Instead of thinking about which way and how you are going to fly round that church spire, you just take the machine up and position it to get the shot you are after then bring it back to you.

I think FPV is very useful and helps a lot of people not just because what you see is what you get on screen but with FPV you are immersive flying so left is always left, right always right etc. The problem comes if your FPV fails and you have lost orientation - YOU SHOULD ALWAYS BE ABLE TO REGAIN YOUR ORIENTATION and bring your bird home !!

 

[wkf94025]

Thanks Editor. I totally get it on stick time as the best way of getting smooth POI shots. With FPV goggles on, and my Futaba sticks set to de-sensitized "filming" gains, I have become reasonably proficient in smooth shots such as POI. However the perfectionist and math/software geek in me knows that the right HW/SW/FW can do some amazing mathematical curves in the sky, and I like the idea of flying over to that spire, pointing the quad/camera at it, and in some very high level language telling it to circle left at 3m/sec and 30m radius, perhaps with a 1m/sec climb thrown in. I believe that day is not far off, even at the Phantom entry level.

My brain is reasonably trained on the left/right reversal when bringing my P2 toward me. But I recognize that's only a small part of the brain training you're referencing, and have logged.

I am looking forward to flying Manual mode on my stripped down P2 with a cheap non-gimbaled FPV cam and iOSD as the only components on board. Then maneuver at sufficient altitudes to hopefully recover before expensive things happen.

Kelly

 

[ladykate]

FWIW, you can get TBE with NAZA 2 (non-Phantom) (or WKM or A2M). The TBE has been well documented in non-Phantom varieties. If you doubt it, then just turn your GPS puck slightly one way or the other from dead ahead and watch the effect. A poorly calibrated compass (calibrated over metal or in an interference area) will cause it, too.

TBE doesn't have to be the exact way described by Ianwood in his long thread about it. It can be simply an inability to yaw in place (creating a big circle instead). An impromptu POI if you will.

If you want to fly manual, you can learn by just going to manual and flipping the switch to ATTI or GPS when you get in trouble (which you will the first few times).

 

[wkf94025]

Yes, counting on quick flip back to ATTI or GPS to save my bacon while learning nuances of Manual mode.

 

[The Editor]

FWIW, you can get TBE with NAZA 2 (non-Phantom) (or WKM or A2M). The TBE has been well documented in non-Phantom varieties.

You are correct but the question was DO I SUFFER from TBE? The answer to that is no because I have set my magnetic declination correctly.
It is a lot easier to do on a Naza M v2 with GPS and takes seconds (once you know your declination angle for your geographic location)

You are right though - The Naza M CAN suffer TBE if not set up correctly (but avoiding or correcting it is very straightforward).

 

[ladykate]

You are correct but the question was DO I SUFFER from TBE?

Nope. That was your answer. The question was whether Naza V2 (non-Phantom) has TBE issues (among other things). To that question, the answer is yes... they all do depending on several issues.

One which drove me nuts for a long while:
I ran into a problem with both my Naza and A2 machines. Found I had to get out of my neighborhood to do a compass alignment. Just too darn much interference. Once I got out into a field clear of everything, I was able to get an alignment that would allow me to yaw 360 without a big TBE swirl.

As Ian pointed out, TBE instances so far reported are a result of misalignment of the compass and the GPS which can happen with any of the control systems. Specifically WHY they are misaligned can vary - from magnetic declination issues to just interference when doing a compass alignment. While one might dream up a mechanical problem that would cause it - it would be in a very small subset.

 

[The Editor]

You are correct but the question was DO I SUFFER from TBE?

Nope. That was your answer. The question was whether Naza V2 (non-Phantom) has TBE issues (among other things). To that question, the answer is yes... they all do depending on several issues.

One which drove me nuts for a long while:
I ran into a problem with both my Naza and A2 machines. Found I had to get out of my neighborhood to do a compass alignment. Just too darn much interference. Once I got out into a field clear of everything, I was able to get an alignment that would allow me to yaw 360 without a big TBE swirl.

As Ian pointed out, TBE instances so far reported are a result of misalignment of the compass and the GPS which can happen with any of the control systems. Specifically WHY they are misaligned can vary - from magnetic declination issues to just interference when doing a compass alignment. While one might dream up a mechanical problem that would cause it - it would be in a very small subset.

Semantics - Not getting into that one!

GPS is not directional so has noting to do with it. It is the magnetometer alignment that causes the problem.

Edit: Sorry, I just re-read my post above and it came across a bit rude - that was not my intention! I Am correct though

 

[ladykate]

Semantics - Not getting into that one!

Yep. That is what all discussions are about. I was answering the original question - not addressing your post/answer (as much). Semantics are important. Our language is full of nuance and it doesn't hurt to be precise.

GPS is not directional so has noting to do with it. It is the magnetometer alignment that causes the problem.

Edit: Sorry, I just re-read my post above and it came across a bit rude - that was not my intention! I Am correct though

I'm not an expert on the exact cause but if you haven't read through the pages on the compass issues, you might want to take a look. GPS can play a part if the compass is wonky. GPS tries to correct based on the compass reading - which is wrong - which causes more error - which results in a big swoop. Hence, in GPS mode (not ATTI or manual) you can get TBE when trying to do a 360 yaw in place. This is another one of those nuance things - TBE can be attributed to several things.

 

[mediaguru]

Build update.

Stumped for two days now trying to throttle calibrate my ESC's. They just beep beep beep forever.

Currently troubleshooting all that. May need to rewire the power setup or perhaps my TX/RX setup is not configured properly.

 

[The Editor]

Build update.

Stumped for two days now trying to throttle calibrate my ESC's. They just beep beep beep forever.

Currently troubleshooting all that. May need to rewire the power setup or perhaps my TX/RX setup is not configured properly.

Disconnect them all and do them one at a time. Make sure you have full throw on your throttle - i.e you have no subtrims or throttle curves or anything set on your TX. Then connect the esc's up one by one and do your calibration. The esc needs to 'see' full throttle travel from 0 - 100% before it will calibrate.

Once you have calibrated them, connect them all up and fire up your machine (minus props) then do several ramps from idle to full throttle at various speeds. You need to be ABSOLUTELY certain your esc's are syncing with your motors. You will hear a ticking sound if they are not - DO NOT ATTEMPT TO FLY if you are suffering sync problems.

 

[wkf94025]

Stumped for two days now trying to throttle calibrate my ESC's. They just beep beep beep forever.

I feel your pain. Each time I undertake some modification/upgrade to my quad, I wonder if the RC Karma gods will be with me or against me. I dread the sink hole of time when they're against me.

Thankfully there are black belts like The Editor out there when that happens...

Kelly

 

[The Editor]

@ mediaguru,

Did you manage to get your esc's calibrated ok?

Are they running SimonK firmware?

 

[mediaguru]

After doing some real dumb things, I realized some of my problems...

I've now gotten 5 of the 6 esc's calibrated. ESC #3 has a problem and will not go into calibration mode. I suspect perhaps a bad ESC wire. Next step is to bust out the multimeter and start testing for shorts or bad wires.

 

[mediaguru]

Multi-tested the motor #3 ESC wires. The signal wire on that motor is bad. So I tied a whole new esc wire to the old one and pulled it through. Then resoldered the new ESC wires to the ESC. That all resolved the motor #3 calibration issues and I now have all motors throttle calibrated.

Last night I also finalized the ESC wiring to confirm all motors are spinning up, and rotating the right direction. All good!

Now reading up on what's next, probably tweaking my SuperX flight controller. Maiden flight coming soon.