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Sep 01, 2019, 01:25 PM
Registered User
Hi, can anyone make a summary for beginners? generates noises that affect the Dragon Link?
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Sep 01, 2019, 02:03 PM
hey whats burning?
metalbender4by's Avatar
https://www.rcgroups.com/forums/show...ostcount=79859

This is a post from a well versed DragonLink owner and I would tend to agree with him.

But on that same note there are a lot of other circumstances that can affect the noise floor.

Edit: "Above -90" would be a smaller negative number. Some one correct me if I'm wrong.
Last edited by metalbender4by; Sep 01, 2019 at 11:50 PM.
Sep 01, 2019, 06:11 PM
Foam Snow
@Vantasstic you're a legend, thanks for this! I don't think I need pixhawk anymore!

Where can I buy? Can't find it anywhere on the usual shops.

Cheers,
Hein
Sep 01, 2019, 08:37 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Thread OP
Quote:
Originally Posted by heinduplessis
@Vantasstic you're a legend, thanks for this! I don't think I need pixhawk anymore!

Where can I buy? Can't find it anywhere on the usual shops.

Cheers,
Hein
I don't think it's available for the general public just yet. Hopefully soon. Mine is a pre-production board that's a little different (layout wise of a few connections) from the manual Matek posted earlier.
Sep 02, 2019, 01:53 AM
Registered User
Popped up in Banggood as alert, but the price is almost doubled comparing to F405...


Wysłane z iPad za pomocą Tapatalk
Sep 05, 2019, 04:54 PM
mdv
mdv
Registered User
Where do you suggest to add the filtering? I am guessing that since the noise shows up on the Dragonlink Antenna that it is coming from the switch node and not the output. I could be wrong. Messing with the switch node (slowing down the edge rates) can make the FETs overheat. Matek should be using a shielded power inductor in this application.

Quote:
Originally Posted by alicecooper
I think the BEC would need to go above one or two amps continuous before it starts regulating with PWM which is when the interference hits.
Matec could easily add a layer of RF filtering to the regulator, even just some ferrite bead inductors with a suitable low esr capacitor would do it for anything in the UHF and above region.
It would require some careful layout design work, but easy enough for their talent level.
Sep 06, 2019, 01:45 AM
Registered User
Quote:
Originally Posted by mdv
Matek should be [...]
When I read this I get the impression that you think that Matek has no idea about power design.

I may remind you that Matek also has several BECs / PDBs in his program. They work and have been for years ... Their FCs also work fine and they update their products regularly.

I think there are some capable people sitting at Matek who don't need external help, but need input from users who really use the products and don't just have theoretical discussions.

My two cents ...
Sep 06, 2019, 05:00 AM
Registered User
I am new to iNav and wanted to give it a test on a plane (mini talon or z84 wing for example)
I first saw the F722-wing from matek and then the new F765-wing.

Is it already supported with iNav ?

Is it better to stay with a F722 for the moment ? (or 405 maybe ?)

Thank you
Sep 06, 2019, 08:58 AM
'Extreme Fabricator'
Quote:
Originally Posted by mdv
Where do you suggest to add the filtering? I am guessing that since the noise shows up on the Dragonlink Antenna that it is coming from the switch node and not the output. I could be wrong. Messing with the switch node (slowing down the edge rates) can make the FETs overheat. Matek should be using a shielded power inductor in this application.
Lowering the peak frequency will not cause more heat in the FET's as the controller chip is designed with the ability to program that set point for max efficiency, that relates more to raising the Q in the inductor. After measuring mine with a CRO, I suspect the interference is actually ringing in the PWM signal, it is hard to stop as it's normally associated with layout and device inductance coupled with very low ESL and ESR capacitors, the ringing frequency is usually a product of the layout more than component selection, but to filter it properly, it would need to have a carefully designed RLC filter to work immediately at the power supply output to minimise signal radiation from the circuit (tracks) in between. It can be done, I just don't think Maytec were aware the problem existed with this board.
Sep 06, 2019, 09:08 AM
'Extreme Fabricator'
I will try a few simple mods to try moving the interference frequency down, it may end up futile but it's worth trying a few tricks.
Sep 06, 2019, 10:19 AM
mdv
mdv
Registered User
I have a lot of experience designing switch mode buck power supplies. I believe the ringing that is causing the interference is on the switch node. This is difficult to control without access to the FET gate drives which are inside the IC on this controller. In this case, the best way to control the radiated emissions is to keep the routing to the inductor as small as possible and use a shielded inductor.

The ringing on the output, if any, should be much smaller amplitude than the ringing on the switch node. Generally, the switch node ringing does not make it past the primary LC filter but it is present inside the inductor. I have solved several radiated emission problems by switching to a shielded inductor for the main LC filter. These generally cost more and are larger than unshielded inductors.



Quote:
Originally Posted by alicecooper
Lowering the peak frequency will not cause more heat in the FET's as the controller chip is designed with the ability to program that set point for max efficiency, that relates more to raising the Q in the inductor. After measuring mine with a CRO, I suspect the interference is actually ringing in the PWM signal, it is hard to stop as it's normally associated with layout and device inductance coupled with very low ESL and ESR capacitors, the ringing frequency is usually a product of the layout more than component selection, but to filter it properly, it would need to have a carefully designed RLC filter to work immediately at the power supply output to minimise signal radiation from the circuit (tracks) in between. It can be done, I just don't think Maytec were aware the problem existed with this board.
Sep 06, 2019, 10:33 AM
mdv
mdv
Registered User
Quote:
Originally Posted by alicecooper
Well, the F405 employs a MP9447 regulator
There are likely several power supplies but I don't think the large one is using a MP9447. Looking at the layout on the Matek website, there is a large, possibly shielded, inductor with what looks like external MOSFETs which wouldn't be the case for the MP9447 which has the MOSFETs built in.

After looking at the MP9447 datasheet, it seems this is definately NOT the one used for the Vx rail; at least I hope not. the MP9447 is only rated to 5A. Matek rates the Vx rail as 8A-10A. Of course, the Vx rail is not the only one which could cause interference.

[edit] to add that the Vx rail power supply controller is too large to be the MP9447. The other two rails, BEC 9V and BEC 5V, are probably using the MP9447.

BTW, the higher the input voltage, the more RF noise that will be radiated from the switch nodes. If we do end up seeing interference from this flight controller, it would be a good idea to keep track of what input voltage is being used.
Last edited by mdv; Sep 06, 2019 at 11:37 AM.
Sep 06, 2019, 11:30 AM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Thread OP
Quote:
Originally Posted by zebu
I am new to iNav and wanted to give it a test on a plane (mini talon or z84 wing for example)
I first saw the F722-wing from matek and then the new F765-wing.

Is it already supported with iNav ?

Is it better to stay with a F722 for the moment ? (or 405 maybe ?)

Thank you
Matek has a link for development iNav firmware for the F765 Wing FC. I'm not an iNav user so don't really know what is/isn't available for their firmware targets. http://www.mateksys.com/?p=5159#tab-id-9
Sep 06, 2019, 01:50 PM
UAV Flight Operations Manager
Any suggestions on what GPS antenna to use for this (or the 405 Wing board)with Ardupilot (ChiBios)?
Sep 06, 2019, 03:08 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Thread OP
Quote:
Originally Posted by philthyy
Any suggestions on what GPS antenna to use for this (or the 405 Wing board)with Ardupilot (ChiBios)?
I use the BN-220 GPS. Small, inexpensive, comes with dupont connectors to attach to the FC pins, gets good satellite lock pretty quick. It doesn't have a built-in mag sensor, but for fixed wing the mag sensor is not needed anyway.


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