Re: USB port voltage
The short answer is 5V. The two outer pins of the common USB port supplies the +ve and -ve 5V terminals. The two inner pins are the data lines.
A slight expansion: The current that can be drawn from a normal USB port is limited. If a connected device tries to draw too much current, the output voltage automatically drops. This prevents overloading and short-circuits. This is one reason why some USB devices like external hard disks do not function reliably with some computers.
As with many technical standards, there are variations and sub-types.
While Wikipedia and other reference sources are valuable, in some cases, the sheer amount of information may be overwhelming. Here's a condensed answer to your question:
The short answer is 5V. The two outer pins of the common USB port supplies the +ve and -ve 5V terminals. The two inner pins are the data lines.
A slight expansion: The current that can be drawn from a normal USB port is limited. If a connected device tries to draw too much current, the output voltage automatically drops. This prevents overloading and short-circuits. This is one reason why some USB devices like external hard disks do not function reliably with some computers.
As with many technical standards, there are variations and sub-types.
tkin
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Re: USB port voltage
^Not much to elaborate. Some mobo designs limit the USB output current more severely than others. The device can't get enough juice and functions erratically or not at all. To circumvent this, some devices come with two USB connectors but stability is sometimes marginal even then.
I've observed this several times. In some cases, I confirmed the fact by measuring the output voltage at the terminals.
^Not much to elaborate. Some mobo designs limit the USB output current more severely than others. The device can't get enough juice and functions erratically or not at all. To circumvent this, some devices come with two USB connectors but stability is sometimes marginal even then.
I've observed this several times. In some cases, I confirmed the fact by measuring the output voltage at the terminals.