Question Problem with interferences on servo with lighthouse

Hey friends,

today is my first Testday with my new Servodrives https://de.aliexpress.com/item/3272...chweb0_0,searchweb201602_2,searchweb201603_53

Now i have a big Problem. my Index Lighthouse boxes, immediately break their bluetooth Connection as soon as the Servo is in Operation. Does anyone have any Suggestion on how i can get around this? I have absolutely no Idea what i can do.

I’m guessing the servos don’t use Bluetooth? If not, it sounds like the motors are electrically very noisy. You may be able to add filter caps, add grounded shields on the motor cables or replace with shielded cables, maybe add clamp-on ferrites at one or both ends of the motor cabling. High current chokes inline on the motor cabling similar to how Avenga76 puts them in his fan circuits might also work. Not sure what your controllers are or can handle, though.

As a last resort, and I don’t remember where I saw it, but I believe you can use USB cables on the Lighthouses instead of a Bluetooth connection but that may limit where you can put your Lighthouses. It’s been a while and there may or may not be any truth to that.

Welcome to the world of RFI!

Hey Bastiuscha, I have no idea how much the power chokes I used clamp RFI, but I would guess a lot. The function in your case would be similar to clamp-on ferrites but probably more effective (but I don’t know that for absolute fact). If your motor controllers are regular PWM H-bridges, you might be able to use inline chokes. I used these guys (but not for noise - I added these to help minimize inductive kickback into my JRK motor controllers to help them better cope with being run out of spec, but they would also help to attenuate RFI: http://www.coilws.com/images/HF5712-700M-60AH Rev.A.pdf. One in series with each motor lead. Build details here: https://www.xsimulator.net/communit...-20-strut-jrks-wind-flying-driving-rig.11281/

Those chokes are rated for 60A 70uH and knocked the peaks off the kickbacks as the PWM did its thing with the motor current. All I can say is I’ve never had issues with RFI on my rig and I also have Lighthouses. These chokes may or may not have had anything to do with that but easily could be.

Much thanks for your awesome help. Lighthouse with usb is not that bad Idea. But i have not found any Instructions on how to do this.

For the Moment i will try EMV Tape.... or a Copper Braid Hose. If this does not help, i will also buy such a Power Inductor. One Question remains: my motor is three-pole...do i use then three of them?

A definite maybe? Not knowing your setup, it’s hard to say. Can you post info? Is this an H bridge setup? Sounds like it might not be with three wires.

But least invasive would be shielding then ferrite chokes. Unfortunately, the most expedient way to go is just try stuff until the Lighthouses work. I think to not use Bluetooth, you just plug the USB cables in but it’s been a long time since I heard this. It could be just a figment of my imagination from years ago. In the RFI (radio frequency interference) even just relocating things can change the effect.

If it is RFI, you could also move the Lighthouses closer to the system to see if they start working. Not as a fix because presumably you like the Lighthouses where they are, but just as a test because radio waves obey the inverse square law. Cut the distance in half and you get four times the signal. If they (or it) start working, it can give you a way to test how effective your shielding or other measures are.

It could also be something as minor as a loose connection or even wire routing. If you can run wires that have the same but opposite current flow (like two motor leads) right next to each other, or better - twist them together - each one’s field will better cancel the other and reduce RFI.

RFI (if that is what this is but it sounds like it is) gets a lot of discussion in amateur radio circles and there are guides for finding and eliminating it. http://www.arrl.org/radio-frequency-interference-rfi

Oh yes, i did a Test with Lighthouse and simply plug usb, but the BT connection was still used.
In my tests, The Lighthouse connection breaks immediately, as soon as the Motor is active. No matter how close I bring the Lighthouse box to the HMD. Sounds like STRONG EMI.

This is a Servodrive. In my first Post is a link of my Motors. I think that could be answer your Question. And one the last Itempicture, you can the the Motor Powerwire(The right one).

Twisting cables is an interesting Idea. Unfortunately, this is also only possible to a limited extent. But I could also include that at the end.

Hey there.
On those AASD controller/motors it's recommended to replace the power cable from the controller to the motor with a shielded one or at least wrap it in grounded aluminium tape or sth.
The EMI-field from those is strong enough to disrupt USB connections. Unfortunately they all come unshielded from the factory unless it's a special order.

@Thanos made a video about it:

Excellent information, @Sverenja! Thanks!

And thanks @Bastiuscha - now I know I was remembering wrong. Sorry about the bad lead.

I would do all the things I did in this post to fix the emi. You can use one choke on each motor, put the three power wires through the choke but not the ground wire as shown in the post.

https://www.racedepartment.com/thre...motion-controller.168360/page-20#post-3047521

@cfischer - that thread is very interesting! For others, one poster found he could cut RFI by 90% just by wrapping his cables in aluminum foil and tying that to ground, but all seemed to agree that stock unshielded cables radiated like a bandit. I’m surprised that equipment that radiates that bad is on the market, though. I’d bet it’s not FCC certified.

I actually have copies of the FCC certificates for the AASD-15A drives and all related motors, but that doesn't stop them from not using unshielded cabling... the cabling is not part of the FCC certification... in industrial environment no one cares about the bit extra emi... they don't use VR in factories... lol

Interesting information. I assumed parts of systems would be tested as a system at some point but don’t know the ins and outs of FCC testing. And I believe the catchall is just if equipment causes unintentional interference to others, the only obligation is to fix it or stop using the equipment but I don’t know the legalities of what FCC certification actually entails.

It may not be a common issue in most factories but there seem to be a number of people who have had this exact issue in homes in this application. And yes, I get that homes may not be where those servos are intended to be operated but whoever packages those systems up and sells them for home use changes that equation a little.

At any rate, it looks like lack of proper shielding is the issue and that’s easily fixed.

But i find it remarkable that even CABLE usb connections are disturbed. I have the feeling that my Brain is being cooked.

Ah...i btw ordered new cables....

@Bastiuscha - I thought it was just the Bluetooth Lighthouse connection that was being interfered with? Any noise making it into other cabling is kind of severe. Maybe separate the servo cables as far from other as possible? Getting shielded cabling sounds like the first and best move, though!

The EMI actually passes through wiring if not well grounded, using all other wiring nearby to resonate... and because of the wavelength of the 10khz being about 30km, it crosses straight into small signal devices if not shielded.

Not that emits that much power to reach 30km, but nearby devices within meters, can get a good dB level of transmitted power that can measure between 0.1v to 2v... enough to disturb VR headset data transmissions

If you're curious this guy gives a good explanation and example of emi affecting things like monitors. Really good method of solving emi as well.

I had not problems with usb so far. "Sverenja" at Post Nr. #7 told this.

Edit: I have a Question! I saw the last posted Video and the Guy was using a Filter. It has a rated Power of 30A.... is that the absolut maximum, before it explodes, or can it shortly above this Value? Because i have 6 Motors. (With 2 by 3 in a row) So i ordered 2 of these Filters. I know, that 3 Motors together are shortly near to 40A on Startup (for the cap filltime). Is this a Problem?

Ok....many Work and Money later...nothing helped.
I changed to shielded Cables, i buyed this Filter from that Video above me and i tested Ferrit Cores. nothing helped.
The shielded Cables i grounded like the Video from Thanos. It didn't help. I even wrapped EMI Tape around it afterwards. Here i get my first "improvement". Sometimes VR works a little bit. (Only in steam vr...not driving).
Then i added Ferrit Cores. Here it getting much worser again. So i had to remove them again.
Finally i have installed the said Filter. This helped a little bit.
The current status looks like this: Sometime i get VR to work, but it ends working always on the same point now... i'm in the Game/Sim and press in Flypt at the gamesource on "connect". In this Second, the Index lost the Tracking.

Maybe try the suggestions on this video about USB devices:

Thank you for this Video. But USB is not the Problem. With Seat and HMD only, the Problem is the Same. Even with Keyboard and Mouse disconncted. And i have to say, that my last Motionseat worked with VR. (2 H.Bridge Brushed Motors)