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geekhack Projects => Making Stuff Together! => Topic started by: mr. rampage on Thu, 08 August 2013, 09:27:10

Title: Do USB cables need to be shielded?
Post by: mr. rampage on Thu, 08 August 2013, 09:27:10
I'm trying to make one of those paracord USB cables, but the paracord's diameter is too small. Would stripping the plastic sheathing and threading the wires through the paracord still work or does the USB cable need the shielding?

Title: Re: Do USB cables need to be shielded?
Post by: Batmann on Thu, 08 August 2013, 09:30:41
You shouldn't have to stripe the plastic sheathing unless you are using a very thick cable (non standard)
It's normal if you struggle, paracord sleeving is a long and tedious process!
Title: Re: Do USB cables need to be shielded?
Post by: mr. rampage on Thu, 08 August 2013, 09:53:09
I noticed that the cables for micro-b usb are much thinner than  mini-b usb. Would I be able to use a  micro-b usb cable and swap the header with a mini-b usb header?
Title: Re: Do USB cables need to be shielded?
Post by: mkawa on Thu, 08 August 2013, 19:32:47
very few usb cables are actually shielded. if you read the usb spec, they specify that all d- and d+ lines be twisted, which provides some signaling, but in the initial 1.0 and 2.0 specs they really kind of halfassed the shielding part of the spec. they basically relied on low voltage and current in the spec to lower EMI. that's why there are a lot of super thin cables out there with maybe like a tiny ferrite bead at the end. in the 3.0 spec, they do specify some kind of shielding for the wire bunch, but i don't think it necessarily has to be metallized (which is the most effective EMI blocker, even for twisted pair cables).

that said, another basically unshielded twisted pair wire spec is ethernet and it works well enough (although at about 2x the wire count), so i dunno. if you're unsure, shield your cable or at least add a noise filtering ferrite bead somewhere (they are cheap!).