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How many Amps can I pull through the USB to the 5V pin?

The short answer is 500mA sustained. You can pull up to 1A for short periods of time, but for prolonged periods the reverse back-feed diode will get very hot and could get damaged. Anything above 1A will likely kill the diode very quickly.

So how can I power all of my current hungry 5V peripherals and LED strips from the 5V pin if I can only pull 500mA from the USB?

You’re not supposed to power them that way. The 5V pin is an output and an input, so you power your current hungry peripherals and LEDs from an external 5V power source and also power your board from that source via the 5V pin.

It’s not just the diode that prevents using Amps via USB here, even with boards that have no reverse back-feed diodes to protect your USB port on your computer, they all still have limits on how much current you can pull through the traces on the PCB, and the plated holes on the PCB itself that you are connecting your peripherals to.

You also have to consider spikes and inrush currents that can easily be caused by external devices connected to your 5V pin – You don’t want those coming back through your board and potentially back through your USB cable.

For more information on what the reverse back-feed diode is and how the 5V pin works on Unexpected Maker boards, please check out the article What voltage range can the 5V pin accept and is it an input and output?.

Updated on June 15, 2024

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