Shielded cables for FPV quads
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- เผยแพร่เมื่อ 23 ส.ค. 2022
- This is how I build shielded cables to connect components in my quadcopters. I don't know how much benefit this has for things like the video transmitter or receiver, but other folks have shown drastic improvement when using a shielded cable to connect your GPS. This helps increase the number of satellites, and also reduce lock times.
Foil tape: www.amazon.com/gp/product/B07...
Paracord: www.amazon.com/gp/product/B07...
Heat shrink tubing: www.amazon.com/gp/product/B07...
Wire: www.amazon.com/gp/product/B07...
Connecting the shielding at one end makes it a pretty nice antenna. Grounding it to your signal ground (or even a power ground) will typically make your noise issues worse. This makes it a pretty good diagnostic tool, in that if your results are equal or better, then you simply didn't need a shield, and are imagining an improvement.
In industry, shielded cables for signal wires is standard practice. Grounding the shield makes it function properly to keep internal EMI from leaking out and external EMI from getting in. Here are some references.
interconnectsolutions.com/resources/understanding-shielded-cables/
instrumentationtools.com/where-should-we-terminate-the-shield-and-why/
@@kyakfsh Thank you for providing links. However...
From your source "interconnectsolutions", the following guidance is violated.:
- "When the shield/screen is grounded at one end only, the grounding is usually made in equipment panel/cabinet at the end with the power supply or the receiver."
(Note: It looks like this GPS without differential signalling, and thus, the ground is a data ground. Attaching your drain wire to one end of the twisted power wires enhances the noise-related ground reference error. Power ground is at your battery connector (before the current sense shunt). That's where this wire goes, when a shield on this wire is needed.)
- "The signal wire shield is never connected to the common side of a logic circuit (this would introduce noise into the logic circuit)."
(Note: The power wires were twisted to keep incident noise common to both. Normally, this is enough, but static transients can be diverted by using a shield to distribute them as they dissipate. Connecting this shield to signal ground, however, turns the static charge into a spurious current.)
More importantly, the data is flowing about 5 inches. The data signal is likely 3-5Vpp, and it's unlikely to get any benefit from correctly applied shielding in any situation that doesn't also interfere with the onboard receivers. Collecting and injecting ambient noise into the data side of your controller's microprocessor ground may give variable results however.
Compared to a short run of directly-wired data, the GPS signal is very faint. If your goal is to keep your digital noise from interfering with the signal to the GPS antenna, then you would shield the volume that the flight controller occupies, and ground that to the power ground (at battery connector), and then ensure that all of the Transmitting antennas are unable to radiate onto your GPS patch (or re-radiate, in the case of the antenna coupling with your shield). If there were a data wire strangely loud enough to interfere with reception, your model has it covered by putting it below the antenna's existing ground plane. You could shield an offending wire and ground it to the previously described shielding cage, but it should be at multiple points around the shield, preferably continuous.
"Simply, don't put a transmitting antenna past the plane of the GPS patch antenna, and it will have the best possible reception for the weight and money." is what I'm trying to say.
Nice video on making shielded wires. However, I have tried all sorts of shielding with essentially not improvement in satellite fix. What does work it mounting the GPS high, higher than the top mounted battery by at least 20mm and ensuring separation from other antennas. From my experience, the GPS just needs clear exposure to the sky and simply up and away from the quad itself. Plus, it is much easier and less time consuming.
That paracord gives it a nice professional look!
using paracord like that is pretty smart idea, I like that, I'm gonna use it next time. Thanks a lot
It blows my mind how many people don't ground the copper shielding. Glad to see you do that. Even certain manufacturers just wrap the wires and don't ground then. Guess some people don't understand how shielding actually works. Awesome work man look clean AF.
I have a roll of woven shielding tape, (nickel, aluminum, silver? not sure what it's made of, but it is conductive) would using woven shielding tape be just as good as this copper tape? not as good?
@darrick.S probably be as good at least. As long as it's grounded it will create a charged field around it blocking signal in or out. I'm sure the better quality of material will create better quality shield. But I couldn't say for sure without actual testing. But I would lean towards better. Just make sure you wrap it up and ground it.
@@xORLOCKx I will take your word for it, I do not have the analyzing equipment I would need to confirm. But you have more experience than I do, so thank you for your time.
@darrick.S I've spent more time with signal transmission than drones themselves. I'm just applying theory based on what I've learned over the years. Grounded and insulated copper shielding is what big company's use. Take the cable that connects to your internet or TV. (Coaxial cable) it's grounded and shielded in copper. Copper is an amazing shield/ground material. With that said there are plenty of other blends than can do the same. I think you will have great results regardless. 😊
simply i'm using small audio cable for vid cable and ground...it work perfect with shielding
Nice work, I used the shielding that dji use for their phantom series(Thin foam with two layers of copper) But could not get the kind of finish you achieved here, I will try your method.
Fantastic, Todd! I needed a flexible sheathing and it never occurred to me to use Paracord!
Glad you found it useful. I put paracord on my motor wires, too, when I want to tidy up the look of my quads. It's nice to up your game every so often.
I will try shilding the GPS wires on my new build. But I would reccomend aluminum over copper, lighter than copper and probably just as effective. (little hard to solder to though :-)
who also think this is the neatest quad on the internet? Brilliant
great tutorial, what size paracord do you recommend for 5inch motor wires? or what paracord is shown here in this video? ive heard 6mm from a buddy but idk what to buy
does this help against signal jamming?
Great video. Thanks! But should you not separete the power wires from the data ones? (white and green)
Very possibly. I'm a mechanical engineer, with a dabble of experience on the electrical side. I did this cable by copying one of the stock cables that connected my ESC and FC boards. But, I really should have a coworker electrical engineer take a look at this video to see if I did things for best electrical noise reduction. My guess is that both the power wire pair and the data wire pair would be individually twisted and shielded.
@todd what size is the paracord? Do you shield every cable on the quad ? Any link to purchase of the products? Thank you !!
On this build I shielded the receiver cable, video cable and GPS cable. The cable between the FC and EDC isn't shielded, nor are the motor cables. I added links to all the supplies in the video description.
Thank you very much . What do you do to the earth wire ?? Where do you attach it to
@@ARMY_RUGS On the GPS wire bundle there is a ground wire, a +5V power wire, and TX and RX wires for digital communications to and from the FC. I connected the shield to the ground wire that attaches to the FC.
Where do you connect that ground cable from shielding to? On the same pad that GPS ground cable?
I connected to the ground pad on the flight controller.
So shield ground wire and the connector pin ground wire be solder together on a ground pad?
Yes, but only on one end of the cable. If you ground the shield at both ends, you can make a ground loop, which is bad.
@@kyakfsh This shouldn't be a problem on battery-powered devices like quadcopters. You mostly only see ground loop issues when connecting two separate pieces of equipment, each with their own reference to ground that are not at the same potential. For self-contained devices like this that operate from "battery ground" and aren't referenced to earth, the shield should be grounded at both ends to avoid acting as an antenna. You'll also get better CMRR. It's worth noting, however, that GPS modules like that probably communicate with digital signals, which are immune to all but the strongest of EMI.
Can we use aluminum foil instead of copper tape..its wraps easily and block the signal interference
Probably won't be able to solder the ground lead to it. I could be wrong. Without ground it's worthless
why do you not twist signal wires?
I was going by how the ESC cable was constructed. But, I probably should have twisted the signal wires also.
Do you feel like it helped at all. No one seems to be able to say for sure if doing this helps any significant amount. In my experience the most helpful thing iv found is just moving the GPS receiver farther away from everything else and/or getting better GPS receivers.
The only way to conclusively prove a difference is to have both shielded and unshielded versions of the cables, and fly back to back flights after swapping back and forth the different styles of cables. I did not do this comparative testing. I just shielded all my cables. I can say that the two quads I built this way have better video range (vista) than other similar builds with unshielded cables. But, that's not scientific testing because there are more changing variables than just the cable shielding.
@@kyakfsh That's why I asked if you feel like it helped. All the times iv seen someone try to test shielding the cables objectively no one has been able to conclusively show anything but I see lots of people adding shielding. So do you feel like it was worth the effort? will you be doing this as standard on your builds going forward? Iv also read that the shielding only matters for the couple inches closest to the GPS and as a good compromise for weight and effort you can shield just a part of the cables, have you considered this? Just looking for your thoughts on doing this beyond your how to video. Thanks,
Where to connect a ground wire ?
There is a signal ground between components. Attach the shield to either end of the ground wire. But, never both ends! That may introduce a ground loop, which is bad.
@@kyakfsh 1. Somebody told me that the best is to connect it to a battery minus.
2. What is it "signal ground"?
Is it a pad on FC where black (-) wire from a component should be connected?
If so, should I solder 2 wires to the same pad?
Much easier is to strip a shield from coax cable and use it.
Yep. That would work, too. You can actually buy copper braided shielding from Amazon, but it's surprisingly expensive.