Robust power connection - It's important for the power pins to make connection before the data lines, to avoid trying to power the device over the data lines.This is important to keep the signal intact in environments with a lot of electrical 'noise'. Shielding - USB connectors are shielded, such that a metal shell which is not part of the electrical circuit is provided.USB connectors are designed to transmit 5V, up to 500mA. These are for power, ground, and two data lines (D+ and D-). Four contacts - All USB connectors have at least four contacts (although some may have five, and USB 3.0+ connectors have even more).It may be possible to force a connector in wrong, but that will result in damage to the device. Polarization - A USB connector can only nominally be inserted one way.However, all USB connectors will have some things in common: In the USB standard, there is a difference between the two, and the connectors on cables and devices reflect this. USB connectors come in two flavors: host and peripheral. We'll discuss this more in the examples section for each individual connector. The term 'mount' can refer to several things: how the connector is mounted in use (panel mount, free-hanging, board mount), what the angle of the connector is relative to its attachment (straight or right-angle), or how it is mechanically attached (solder tab, surface mount, through hole). Mount - This one has the potential for being confusing. It's important that you select a connector with a suitable life for the application. A USB connector may have a lifetime in the thousands or tens of thousands of cycles, while a board-to-board connector designed for use inside of consumer electronics may be limited to tens of cycles. Datasheets usually present that information in terms of mating cycles, and it varies widely from one technology to another. Mating cycles - Connectors have a finite life, and connecting and disconnecting them is what wears them out. The pitch of the pins on the headers on a standard Arduino is.

Molex connector catalog