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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. StarTech.com does not sell power supplies for these hubs and a power supply must be provisioned separately.

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.

Power supplies are sold by a number of online distributors and resellers. StarTech.com does not provide any official recommendations for distributors or resellers.