# Product FAQs

### How to

#### My USB 3.0 hub did not come with a power adapter. How do I power it externally?

To externally power your USB 3.0 hub, you need to wire power into the terminal block. Simply find a power adapter with the correct power specifications and wire it into the terminal block to provide power.

Note: Having too much amperage is fine because the USB device will only pull what it needs. Having too little amperage could result in performance issues, especially with high-powered USB devices that are USB-powered only, like external hard drives.

A basic USB 3.0 port provides 5 volts (5V) at up to 900 milliamps (900mA / 0.9A).

Short (no math) version

This device (ST7300USBM) takes in anywhere from 7 to 40V and the maximum amount of amperage you require is 4.5A; therefore, the maximum amount of wattage that you need is 31.5W.

Long (math) version

Note: Wattage (W) = Voltage (V) x Amperage (A)

Voltage remains constant at 5V, so the equation looks like this:

W = 5V x (7 ports x 900mA)

W = 5 x 6.3A

W = 31.5

To find out the total amount of amperage your power adapter needs, you need to look at what voltage your power adapter uses and find out the amperage.

Note: Amperage (A) = Wattage (W) /  Voltage (V)

We will show the highest and lowest amperage required.

If you are using a 7V adapter

A = 31.5 / 7

A= 4.5

If you are using a 40V adapter:

A = 31.5 / 40

A = 0.79