450 Sized Quad "Grasshopper Effect" Problem

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Pyrslx

Member
Hey everyone, new here but have a question about my new quad I built.

I built a 450 sized quad using:

DJI clone 450 platform
1000kv Motors
1045 Props
KK2.1 Steveis newest firmware
30amp esc's
2200mah Turnigy 3 Cell Battery

When flying I will hover pretty well 20-30 feet in the air, and then dip down all the way to the ground. I will counter it with a throttle adjustment and the amount required will send me up 3x the height if I don't lower it right away and the process continues.

I know there is supposed to be some constant throttle adjustment when flying, but this makes it almost that I cant even go left or right very well without dipping way down and back up.

My only other experience flying was with a Syma x5c, and it had nothing close to this, so it leaves me to think I have an actual issue somewhere with my quad.

Any help will be greatly appreciated, I recorded a video of how it dips quite a bit, and might help get the point across.

Thanks again, and I hope to be an active contributor to this forum :D
 
I spent a good deal of yesterday and today trying out different P and I gains, and none seemed to really change much. It almost feels like the motors lose a bit of power resulting in the drop (without actual power loss).
 
glowingturnip said:
sensor tests ok ? maybe a dodgy accelerometer or gyro
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I checked them and all seem to be working fine, I get "Ok" For them all when tested.

GJH105775 said:
Could be, however most quadcopters with the KK board will go up or down a little when you add yaw/rudder. Have you yet flashed with Stevies pro?
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It will go down when im trying to hover it too, it feels almost impossible to keep it at a decently stable height for more than a second or two, since it will fall, and the amount to counter that will make it go much higher than the altitude I wanted to hold it at.

I have an APM coming and should b here next week and im gonna try it out to see if it has just as much dipping, and I also want to try the altitude hold on it for when I get my fpv gear.

Jackson said:
Probably be best to just reset the KK2 and start over, just a 15 min job.
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Yah im gonna try resetting it today just to see what happens, and hope it helps!
 
What is your weight to thrust ratio, you usually have to compensate with throttle when you yaw or pitch, but if you don't have enough overhead you may not be able to compensate.
 
GJH105775 said:
What is your weight to thrust ratio, you usually have to compensate with throttle when you yaw or pitch, but if you don't have enough overhead you may not be able to compensate.
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Im not actually sure what it is right now, just looked at the weight of my parts and its about 764 grams, probably 800 with the power distribution board.

Could it possibly be my battery not able to supply the amps needed? It's a 20c battery with 30c burst. I looked up the thrust of similar motors (980 kv with 1045 props and it says max thrust of 900 grams) I assume thats per propeller.
 
Pyrslx said:
Im not actually sure what it is right now, just looked at the weight of my parts and its about 764 grams, probably 800 with the power distribution board.

Could it possibly be my battery not able to supply the amps needed? It's a 20c battery with 30c burst. I looked up the thrust of similar motors (980 kv with 1045 props and it says max thrust of 900 grams) I assume thats per propeller.
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The battery will oversupply if you draw it, if you did not have the required amps you'd puff the battery.


What is the capacity of the battery. Also read this to better understand C rate.
 
Its a 2200mah turnigy. The reason I was thinking it could be the battery is because the motors can draw up to 10 amps each apparently, so if the battery can only supply 20 with a burst of 30 then it might be pushing it, of course it wont be drawing that max amperage the whole flight, mainly only if I push the motors to their full power, or if im flying very recklessly. But if they are taking half of their max draw (5 amps) its basically maxing out the battery at its discharge rate.

I don't know if its good to be running at the full discharge rate of the battery. But I could be totally off.
 
Pyrslx said:
Its a 2200mah turnigy. The reason I was thinking it could be the battery is because the motors can draw up to 10 amps each apparently, so if the battery can only supply 20 with a burst of 30 then it might be pushing it, of course it wont be drawing that max amperage the whole flight, mainly only if I push the motors to their full power, or if im flying very recklessly. But if they are taking half of their max draw (5 amps) its basically maxing out the battery at its discharge rate.

I don't know if its good to be running at the full discharge rate of the battery. But I could be totally off.
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You may want to read how C rate works, 44 amps constant and 66 amps ~10 second burst. It would make more sense for them to put actual amps on the battery, but one this is more correct, and the little bit of confusion can make them a little more money anyways.
 
Well then if its not the battery under-powering the motors, and since the motors should have a decent amount of thrust for this configuration, i'm not sure what it is that could be causing this.
 
Try the new FC, or flash the KK. That may fix it. The problem is in the math that the FCB is doing.
 
GJH105775 said:
Try the new FC, or flash the KK. That may fix it. The problem is in the math that the FCB is doing.
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I have my apm coming and should be here next week! Hopefully that keeps things a bit more stable in the rise and fall. Also with the Altitude hold that will be a nice backup for when I get all my fpv equipment. :)
 
GJH105775 said:
Yeah, but try to not rely on alt hold and GPS hold.
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Yah I plan on trying it out stock, and try to hone my flying skills that way, but if the altitude hold works really well with the barometer I might try to learn with it on and just try to learn how to keep my bearings and orientation under control since its a huge issue for me.
 
Pyrslx said:
Yah I plan on trying it out stock, and try to hone my flying skills that way, but if the altitude hold works really well with the barometer I might try to learn with it on and just try to learn how to keep my bearings and orientation under control since its a huge issue for me.
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That is the biggest problem for most people. Yeah, it would be good to start there because you can't learn on a broken quadcopter :).
 
For sure, i'm trying my best to go out everyday and learn, and try to keep myself situated, its super hard for me, but if I don't have to worry about keeping altitude it will be slightly easier. :D

So far I only try keeping my orientation and mess with pitch and roll, and when my quad gets pointed at an angle, turn it back. But boy, when I throw yaw into the mix, with keeping myself level, and pitch and roll, it's gonna be a doozie of a time!! Haha
 
your setup sounds a lot like mine (dets in my sig), only diff seems to be that my ESC's are 25A. So it should fly...
 
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