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by morcheeba 1558 days ago
Besides the wiping, these connectors are missing two other features: ESD protection and connection-sequencing.

Most user-facing connectors have a metal shield around them connected to frame ground. The idea is that any ESD shock goes safely through this first instead of to a sensitive data line.

Connection-sequencing ensures that the ground and power is connected before data lines are. If you look inside a cable-side USB connector, you'll see that the inner two wires (data) are recessed a little so that the power connectors go first. A device that is connected without power can (through its ESD protection circuit) attempt to draw power from data lines... this can cause damage because most data lines can't supply the current to power the entire device.

2 comments

You don't know if they ESD protection or not. There are loads of tiny little ESD protection ICs/diodes that can handle many inputs. Just put them very close to the connectors and you should be good to go from an ESD perspective. You don't need a metal shield around everything to protect against ESD.

Every USB device connected to your PC right now probably has a little ESD protection IC in it. Usually sitting right next to the USB connector (as close as possible).

I think you could effectively connection sequence this interface? Though it'd be electronic sequencing rather than a physical one like on usb ports, you could make it so that a particular non-symmetrical set of pins need to be in a certain position before power is delivered through any power pins. Assuming there are multiple grounds, it could be continuity through all the ground pins that would allow power to flow.

And since the snap-in boards are all rigid you don't really need to worry about the possibility that contact will be made in like.. a rolling way. Either the pins are on the board or they're not.

But I'm not an EE, just a hobbyist, so maybe there's something I've missed there and what I'm thinking is way more complicated than I think.