Sinister 770 Quad Build

[Derek]

Went to my local DIY store and found 8 lock nuts. I was impressed! Ive got them installed and, although they dont look the prettiest, they are quite tight. Im happy.

Now i need to ask....how do i range check my rx on a quad? Range checking a plane is easy...step back and move the control surfaces. Quads dont have control surfaces. If i step back a good distance and arm/disarm the board (props will spin when armed), will that be suitable?

[Derek]

Ok guys...im being faced with something i dont understand. What is "motor desync'ing" mean? Ive been told that, although esc's can be sync'd in blheli suite, the motors can desync and shut off. I dont understand this nor do i want this to happen with my build.

Also....my Little Bee esc's are soldered to my KISS fc....how can i get them connected to the blheli suite? Ive been told that the only way to do so would be to flash the KISS fc with Betaflight and then set up a passthrough. This is getting confusing to me and i dont understand.

[Graham Lawrie]

https://github.com/betaflight/betafligh ... ss-through

[Graham Lawrie]

https://www.youtube.com/watch?v=YWLk4qcQcvw

[Graham Lawrie]

You have probably seen Painless 360 stuff but the has most things on Kiss on his channel:)
https://www.youtube.com/watch?v=q__qSBw8RQ8

[Derek]

Lol.....why didnt i think of Painless360? That guy is brilliant! Thanks Graham!

[cml001]

That's where I learned.. & still reference most of my FPV/quad info.. that guy rocks!

[Derek]

Well thats unfortunate! I wanted to maiden hover my 770 for the first time. Plugged in battery number 1 and esc number 1 went up in flames. Im gonna check over the wires and see where i messed up

[Graham Lawrie]

not so good Derek:(

[Derek]

Nope lol....not good at all. Its odd....all the wires are soldered where they are suppose to be, too. The 22 gauge negative wire shows a lot of hot spots. I had it piggy backed to the negative wire that get soldered to the PDB. I have all the wires like that.

Oh well....its a part of the process, i guess lol. New esc's will be ordered and then the wait begins again.

I did speak with the guy, Brian, that inspired my build. He tells me that this build is not a mini quad and should not be treated as one. All the settings need to be slowed down and D Shot is probably not going to benefit my build at all. He also tells me that the KISS fc is probably too fast for this build. Brian has 6 Super Class builds and each one is running either CC3D boards or some sort of F1 board.

So, id like to ask this....do you guys think the KISS fc is "too much" for my build?

[cml001]

I wouldn't think so... ur settings in the FC(any FC) will dictate the response via stick input.. is just keep it toned down... but to be honest I know nothing about building a large quad as the one u r building.

[Derek]

Lol....in truth...i know nothing about building a large quad too. Ha ha ha

[cml001]

In my mind, the newer, faster boards would be better. They have faster gyros... so they would better stabilize...

[Derek]

I agree with you, Clay. In my mind, newer and faster would be better. But Brian is telling me the the newer fc's compensate so fast that they cause the motors to desync....therefore the quad falls out of the air. I dont fully understand how a motor can desync....but this info is coming from a guy that has built several big beasts.

Im trying to absorb the info that he's giving me but, in the end, I think its gonna come down to my own "trial and error" experiences.

[KevG]

With a betaflight fc you can turn down the refresh rate Hz of the gyro and loop time, don't know if you can with the kiss setup though

[Derek]

You're right, Kev. That's exactly why im gonna take the kiss fc off and put it in my parts bin for now. I have 2 Flip32 boards in my parts bin and im gonna install that. I dont know much about turning down the refresh rate Hz nor the looptime but im gonna research those. At the very least, ill be more familiar with the firmware and I can use my laptop for field tuning because I know Cleanflight/Betaflight can be used on my Windows 10 laptop....the kiss gui doesn't work on my laptop..just my windows 7 PC.

[KevG]

its easy Derek its all on the config screen left side about half way down, and I think its a drop down menu, the higher hz the faster the refresh rate is.

[pvolcko]

When we talk about "dsync" it can actually be two different things now that we're in the world of high rate ESC protocols.

It used to be that this referred only to the issue of the ESC losing track of where the motor can was, resulting in it misfiring the motor and causing huge electrical issues in the ESC that would result in it overloading and potentially starting on fire (if protection mechanisms didn't cut motor power entirely in time).

Now, though it can also refer to the issue of an ESC losing sync with the time base of the flight controller in it's signaling to the ESC. With the advent of oneshot and multi-shot protocols which strive to greatly speed up the rates of signaling from the FC to the ESC, but ultimately still relying on PWM type signaling that involves ESCs measuring pulse durations to determine throttle levels, it becomes increasingly possible for the ESCs to get their timing circuits out fo sync with the FC (and with each other). With slower protocols this isn't a problem because the errors between ESCs and between FC and ESC result in far less impact on the final detected throttle value in each ESC. But as you increase the signaling rate, the errors become larger pieces of each transmitted throttle value. As an aside, this is why DSHOT was created, to overcome the reliance on pulse width timing as the means of conveying the throttle value. DSHOT actually uses a more typical binary signaling scheme, which means it's more robust against oscillator frequency drift between the components (as well as electrical noise) and it can incorporate checksums and other means to allow the receiver to verify that the received value is correct.

How does all this apply against your mega quad project?

Big means slow. Not necessarily in raw velocity of the quad, but in terms of how fast things can react and effect changes in direction, speed, and momentum it is going to be slow compared to a 150 or 250 class quad setup. The rotating mass of the props is huge by comparison, same for the rotating mass of the model about it's axes. As a result all the one shot/multi-shot/dshot stuff is kind of wasted and even counter productive on a machine this big. The protocol speed itself isn't so much the problem as is the fact the ESCs are trying to actually utilize the fast changing throttle values on a big slow to react prop. If the firmware doesn't fully decouple the motor control logic from the throttle input logic, and allow the throttle value to latch against when the ESC can actually use it with the motor it's controlling, then there will be problems. And then there is the motor/esc timing issue. Because it's such a large prop a 20A class race style ESC really has no chance of doing what it would normally be able to do with a 150-250 class prop. Unless you size up the motors and ESC to keep the same kind of power/mass ratio as on the smaller class quad, you're going to end up needing to run an ESC more in a traditional airplane type of mode and set up the FC to deal with the slower reactions on the motors.

Active braking probably isn't advisable. Use the slower protocols ESC (pwm, oneshot125) and slower ESC refresh rates (the rate it tries to control the motor at). Etc. This thing is a lumbering giant compared to what all this new fangled control tech is designed for. You're going against the trend of smaller, faster, more nimble, twitch response, etc. so don't feel compelled to use the latest and greatest, it may well fight against you in this case.

[Derek]

...and in usual fashion, Paul chimes in with a very lengthy explanation....but this time, I think I understood "most" of what he was talking about, lol.

Paul....thanks very much for that! Yes, I am going against the grain with this build. I've been the target of quite a bit of negative comments on Facebook. But, I've seen many other very large builds fly and I was immediately mesmerized....meaning, I had to have one. I know that I probably don't have a proper knowledge base to pursue such task but I really want this build so, in the end, I'm thinking that I"ll learn something.

Active braking is not going to be used. That's probably one of the few things that I was 100% sure of. Slower protocols and refresh rates....that's something that I've recently been aware of (didnt know any better). This is one of the biggest reasons that I am going to remove the KISS flight controller and install a Flip32 fc with Cleanflight. Going back to Cleanflight will be a positive change, I'm thinking, because I'm more familiar with the firmware and the setup.

I did order more esc's, because one of them caught fire the other day when I attempted a hover test. I think I mentioned that above. I ordered 3 esc's....one of them to replace the burnt one and the other two esc's are for spares....just in case. Once I get the Flip32 and new esc installed, I'll quickly take the esc protocol down from DSHOT300 to OneShot125. I'll have to research a bit about slowing the esc refresh rates.

[cml001]

U can adjust it in KISS.