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# How do I provide external power to my industrial USB hub?

Industrial USB hubs offered by StarTech.com require an external power supply that connects to the terminal block on the hub.

To select a power supply, you need to determine the maximum power requirements (wattage) of the hub.

The equation you should use to determine the power requirements is P = 5 * I * N, where the following is true:

• P is the power in watts.
• is the voltage of the USB port.
• I is the current of the USB port in Amps.
• I = 0.5 A for USB 2.0.
• I = 0.9 A for USB 3.0.
• N is the number of USB ports.

For example, a four-port USB 3.0 hub's maximum power requirement is P = 5 * 0.9 * 4. Therefore, the minimum wattage of the power supply for the four-port USB 3.0 hub is 18 watts.

When you determine the power requirements of the hub, you can choose a power supply. The following criteria must be met when you select the power supply:

• The voltage must be within 7 to 24 or 7 to 40 Volts DC, depending on the specifications of the USB hub.
• The power supply must convert AC to DC (no AC output).
• The power rating is equal or greater to the requirements of the hub.

Most power supplies come with a rating in volts (V) and amps (A). To determine the current in amps, use I = P / V, where the following is true:

• I is the current of the power supply.
• P is the calculated power of the hub.
• V is the chosen voltage of the power supply (between 7 to 24 or 7 to 40 volts).

For example, if a hub requires 18 W and you choose a 12 V power supply, the current of the power supply would be I = 18/12, I = 1.5A.