USB connectors

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Re: USB connectors

Post by x55 » Mon Jul 27, 2020 12:04 pm

cdmackay wrote:
Tue Jan 08, 2019 8:05 pm
I had read that the power pins of the USB connection may be slightly longer, so that power is up before the data pins are connected. Whether that's true or not, I don't know, and I think it referred to the USB-A (i.e. PC/host) end.
Yes, it refers to USB v1 Type A 'plugs'. On inserting the plug the grounded metal shield makes contact first, then the longer 'pins' establish a steady power supply (in a USB connection the 'host' always supplies the power), then the data lines are connected. In MiniUSB and MicroUSB connections there are no 'longer' pins but a fifth ('ID') 'pin' that, in conjuction with some simple electronics, is used to determine which is the host and prevent conflicts that way. MiniUSB and MicroUSB 'receptacles' can also come in an 'AB' format that accepts either type of plug and utilizes the ID 'pin' to sort out which is which in "On the Go' connections. In charge-only cables the data lines should be shorted out at the device.

In USB connector are there no 'pins', but flat strips positioned against a solid substrate to form an arrangement that makes the connections much more robust and durable (no actual pins to get easily bent or broken). Also, where possible stress points are moved into the cable, which makes for easier and cheaper replacement if wear does cause a problem. In terms of durability, v1.0 connectors are the least rated, then Mini connectors then Micro connectors, with C connectors providing the highest specification. Each one of that sequence is about an order of magnitude more durable than its predecessor.

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