Building compact and burying cortex low and below, we were concerned about the USB having interference from surrounding metal. So, we are looking to take advantage of Rule R7j
“A USB extension cable may be used for the sole purpose of remote mounting of a VEXnet key.
The key must be mounted in the following manner. (See the below image for reference)
i. The VEXnet key must be mounted such that no metal is touching the key above the
VEXnet logo.”
Looking at options, most usb extensions have way too much cord. But found this http://www.usbfirewire.com/Parts/rr-asafpm-xxgr.html in 10 and 20 inch and like ability to secure with screws (though may have to drill out to use legal screw sizes). Cost is not bad but don’t know shipping yet. Leaning toward 20 inch. Any technical reason why these shorter USB 3.0 extensions would not be a good investment?
tbh in this case i used a usb2.0 cable, fairly long (a sony cable from one of my cameras) and it worked well … found that range slightly better as before vexnet key was under alot of stuff … this year i have just mounted the cortex differently, from a technical standpoint, only thing i can think is small amount (v.small) voltage loss, but all i know is they work well. Just the mounting rule that makes me always makes me think twice
Jpearman–no problem with accessibility. The bot has scissor lift sides with an elevated drivetrain. The cortex is mounted at 2.5 inch height and 2 inches below drivetrain deck to allow intake to reach all the way through the scissor lift walls to the rear. On/off and battery input on the cortex is accessible from top of /bottom of deck and the elevated space on the side.
And Team 80-Giraffes–Monoprice definitely has them cheap. I can get ten 1.5 ft. 2.0 for $.83 per unit.
The screw mounting was desirable because a very light custom lexan mount could be made. I guess at that price we could mount it to the lexan with zips. Thanks
From the experiences that I have had, having an USB extender creates 2 connections, so you have twice the risk of losing connection if either connection fails.
When mounting the VEXnet key, remember that another robot might knock into it.
Secure it with zip ties, lexan, rubber bands or something else!
If you are paying for shipping anyway, you might want to pick up more than one size. Also, too long of a cable could be annoying. (1.5 ft is plenty in my opinion.)
There is zero technical reason to use USB 3.0 cables. They essentially provide some extra “go faster” contacts that aren’t used in USB 2.0 applications and personally I think are less robust than non USB 3.0 cables.
I doubt the VEXnet adapters use USB 2.0 Hi-Speed 480Mbps mode too so even USB 1.1 cables would probably do just fine especially since you’re only talking about a short distance and not the 5m maximum.
Make sure it’s a shielded USB extension cable, some cheap stuff isn’t. You can check this by measuring the resistance between the connector housing at each end.
Use something plastic (polycarbonate, sprocket, or whatever) to support to VEXnet key so it’s kept rigidly mounted relative to the USB cable socket. Make sure it can’t wiggle as there’s nothing worse than breaking down during a match just because of a connection problem!
I ordered a pair of 1.5 ones from my favorite cable site, they arrived yesterday. Not sure how I’m going to coil up the extra 13.5 feet. (They shipped me 15’ cables in error) :rolleyes:
