Revolution with GPS HELP!!!!
« on: December 04, 2017, 11:04:47 pm »
Hello everyone.

I recently built a quad and i need some help with the GPS and Mag. I bought a 500mm frame, i am using Revolution as FC, RadioLink SE100 GPS module, QBrain 4in1 ESC and Multistar 700Kv motors. I will post the links for everything below.
So when i had build with no GPS everything was fine. I balanced the pros just fine and even from the first flight it was perfect. No drifting, no vibrations no nothing. Just spot on. I believe it is also important to say that when i used the vehicle setup wizard i chose the current tuning as model and then i left everything in default and i was very surprised with how much stable the quad was. Later i also tested different modes (AttitudeHold, Vario etc.) with no problems and no tuning.

After that i wanted to go to the next level by adding a GPS. After reading in this Forum and on LibrePilot Wiki i bought from HobbyKing the RadioLink SE100 GPS module with Mag. I had to change the connectors a bit to fit to the smaller ports on the Revo and i placed the GPS on the frame with no mast. I didn't place it on the mast because the frame is big and i believe i have no interference. Then i began to calibrate the sensors. I was quite successful from the start with the aux Mag between 0,2%-1% error. Yesterday i went for a test flight to see what that GPS can do. It was a DISASTER. When i arrived to the "test" field i powered everything up and connected the opLink to the laptop to see the data. It quickly locks 17 sats but the Mag was to 2,5% error. After that i tried to fly. I tried to fly three times and three out of three the quad started to climb with nose up. At the fourth try i applied throttle more aggressively and more instantly at around 50% and i managed to get the quad of the ground. After that it started to drift relative fast backwards, meaning the motors to the nose was spinning more quickly. I got frustrated and i decided to change from GPS Outdoor to Basic Complementary just to play a little. It was a little better but still the nose wanted to go up first. I successfully take it off and when i put it in AttitudeHold everything started to falling apart. When i changed to AttitudeHold i was around 8 meters above ground. The quad gone up and dove very aggressively +- 3 meters i believe and then i landed it.

So. Before i installed the GPS everything was perfectly fine. After the GPS everything went sideways. If i had problems only with the GPS i would search it more but now the whole quad is completely uncontrollable. Also after the first mag calibration after a while the error goes up and up around 8% and stays there. I recalibrate and it happens again. The only calibration i haven't done is the thermal, because to be honest i am scarred a little. Unfortunately i haven't enable logging at the GPS test flight so you can see what's going on. I find it very difficult to calibrate that stupid aux Mag and it keeps need to calibrate every time.

Please help me because i am ready to throw everything away and buy different FC and GPS.   


Re: Revolution with GPS HELP!!!!
« Reply #2 on: December 05, 2017, 01:47:49 am »
Is your GPS/mag mounted with arrow or whatever pointing forward?  It is critically important to mount it pointing in the correct direction.

Please post your settings file (uav file) from file -> export uav settings

When you go to Attitude->Magnetometer you should have:
mag usage: auxonly
mag type: flexi

your aux mag orientation should be 0,180,0 or 180,0,180

and look at the blue axis bars on the right side as you rotate the model around.  Numbers there should stay very low, like +-2 or so?

and when you look at Flight Data page, the PFD (upper left) might jitter a tiny amount, but not be flipping all over the place.

and it looks like this GPS does Ublox protocol.  I have had problems trying to get NMEA stable use Ublox protocol, not NMEA.
« Last Edit: December 05, 2017, 02:04:30 am by TheOtherCliff »

Re: Revolution with GPS HELP!!!!
« Reply #3 on: December 05, 2017, 11:21:50 am »
The GPS is mounted correctly and the three bars are at zero with 0,180,0. In the PFD tab when i am outdoors everything is perfectly fine and stable but indoors i have some tilt problems but i believe that is to be expected. The GPS is indeed Ublox and is working great with the sats.
The uav file i will post is with I2C disabled (but i am not sure) because i was trying some things and the second one is after i reset the whole board but i haven't the time to calibrate the mags.
Also after i reseted the board i have some strange behaviour from the motors, like at very low throttle input they are turning fast. Not very fast but fast. At the calibration the starting point of the motors is around 1380 μ/s

Re: Revolution with GPS HELP!!!!
« Reply #4 on: December 05, 2017, 06:49:24 pm »
Also today i performed a indoor test flight after the reset of the FC. Everything was perfectly fine. The quad even indoor with the ground effect was very stable and with no sudden moves and no drift. I believe given the results that when i go outdoor the flight will be excellent.
The one thing i can't understand is the mag calibration. Let's say i calibrate the mags outdoor in one random location and then i go to another location to fly it. Why when i change locations the mag error goes through the roof? I am talking about 5-10 km between the two locations. Should i calibrate the mags every time i go to fly the quad?

f5soh

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Re: Revolution with GPS HELP!!!!
« Reply #5 on: December 05, 2017, 08:15:48 pm »
Calibration should be ok when you move to another place.
Some thing to consider is calibrate Mag with all the accessories and battery same as when you do the flight.

A simple Lipo saver can disturb the mag and if mounted differently can change all the Mag reading.

It should be great if you can post some log files.

Edit: About config file you should set the mag usage to "AuxOnly"
Be sure the auxmag/GPS is away from strong currents and all the magnetic sources when you calibrate. (Gimbal, lipo saver, buzzer....)
Please post pictures for your setup.
« Last Edit: December 05, 2017, 08:21:18 pm by f5soh »

Re: Revolution with GPS HELP!!!!
« Reply #6 on: December 05, 2017, 09:57:03 pm »
Calibration should be ok when you move to another place.
Some thing to consider is calibrate Mag with all the accessories and battery same as when you do the flight.

A simple Lipo saver can disturb the mag and if mounted differently can change all the Mag reading.

It should be great if you can post some log files.

Edit: About config file you should set the mag usage to "AuxOnly"
Be sure the auxmag/GPS is away from strong currents and all the magnetic sources when you calibrate. (Gimbal, lipo saver, buzzer....)
Please post pictures for your setup.

Thanks for you advice. Always i am selecting the aux mag and also i now all about how to calibrate and how to install the gps module. But besides that even if i do everything right when it is time to fly everything are bad. I need ideas expect the usual.

Re: Revolution with GPS HELP!!!!
« Reply #7 on: December 05, 2017, 10:19:27 pm »
I added the third layer you see in the photos to get extra space because of the gps. The only thing that is somewhat close to the gps is the Lipo checker that has two beepers on it, but i only use it to check the battery on the ground and not while i am flying.

f5soh

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Re: Revolution with GPS HELP!!!!
« Reply #8 on: December 05, 2017, 10:25:24 pm »
You need to put your GPS/AuxMag in a mast, away from Magnetic sources.
Better for Mag and also GPS receiving, this is too close from others components.

Quote
Lipo checker that has two beepers on it
There is magnetic material inside the two buzzers so put away while calibrating or flying.

Re: Revolution with GPS HELP!!!!
« Reply #9 on: December 05, 2017, 10:53:00 pm »
You need to put your GPS/AuxMag in a mast, away from Magnetic sources.
Better for Mag and also GPS receiving, this is too close from others components.

Quote
Lipo checker that has two beepers on it
There is magnetic material inside the two buzzers so put away while calibrating or flying.

Are you sure?? The frame is really big. Also there is not enough electricity through the wires to create so much big magnetic fields. But i will try it. I will change the position of the checker to the back of the quad and add the mast

f5soh

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Re: Revolution with GPS HELP!!!!
« Reply #10 on: December 05, 2017, 11:03:02 pm »
Quote
Are you sure??
Yes.
The cause of magnetic fields is not 'electricity' but current and how many space there is between wires (so solution can be reduce space by twisting wires)
Battery can create magnetic fields and can vary from one battery brand to another.
Power PCB where you connect power wires can create trouble as well.

One test you can do is monitor the Mag using the scope tab and Magnetometer scope (enable the Window > Enable the "Edit gadgets mode" to choose scopes to display) and move your checker around the Mag.

Re: Revolution with GPS HELP!!!!
« Reply #11 on: December 05, 2017, 11:08:37 pm »
Quote
Are you sure??
Yes.
The cause of magnetic fields is not 'electricity' but current and how many space there is between wires (so solution can be reduce space by twisting wires)
Battery can create magnetic fields and can vary from one battery brand to another.
Power PCB where you connect power wires can create trouble as well.

One test you can do is monitor the Mag using the scope tab and Magnetometer scope (enable the Window > Enable the "Edit gadgets mode" to choose scopes to display) and move your checker around the Mag.

Because i know some things about magnetic fields except the beeper i don't believe the wires from the motors are the problem. Nothing else i close enough. But thanks again and i will try tomorrow to fly and get back with the results.

f5soh

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Re: Revolution with GPS HELP!!!!
« Reply #12 on: December 05, 2017, 11:12:29 pm »
If you are sure about magnetic fields and power wiring, don't try :)

Re: Revolution with GPS HELP!!!!
« Reply #13 on: December 05, 2017, 11:45:51 pm »
If you are sure about magnetic fields and power wiring, don't try :)

I will try because i can't be 100% sure  ;)

Re: Revolution with GPS HELP!!!!
« Reply #14 on: December 06, 2017, 12:52:22 am »
At the calibration the starting point of the motors is around 1380 μ/s

That is very high and is probably exactly this problem.  After ESC calibration you should do ESC neutral setting.  Most people find that about 1070us is a good value.  I recommend using about 20 higher than "good smooth low value" to help when the ESC gets warm and the timing changes.