General > General Technical Chat

Measuring max output current of a USB port.

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balnazzar:

--- Quote from: pcprogrammer on October 21, 2022, 12:41:40 pm ---Do you know the motherboard used in your computer. It might be able to find the specifications for it.

--- End quote ---

Asus z690-P.

But I didn't find anything in the general (cosumer oriented) specs.. How can they omit those informations??

balnazzar:

--- Quote from: tunk on October 21, 2022, 12:37:04 pm ---Maybe something like these:
https://www.ebay.com/itm/294572711871
https://www.ebay.com/itm/394010597121
Wouldn't know, but you may risk damaging the port.

--- End quote ---

You mean by putting too much load upon them? From usb 3.0 onwards they *should* be protected against that..

Ranayna:

--- Quote from: balnazzar on October 21, 2022, 01:29:01 pm ---How can they omit those informations??

--- End quote ---
Likely because they follow the USB Specification. 100 mA without negotioation, 500 mA with negotiation on USB 2, 900 mA with negotiation on USB 3.
Beyond that and for higher voltages than 5 Volts, you need USB-PD. If USB-PD is not specified, don't expect to have it.

These values are the minimum. More is quite likely, especially the 100 mA limit without negotiation is often not followed, but drawing more *may* overload the ports and cause them to shut down. Or, if ASUS cheaped out, gross overloads may even damage the ports, or the controller chip, permanently.

balnazzar:

--- Quote from: alm on October 21, 2022, 12:44:22 pm ---What is the host? The max power modern USB-C ports on a computer or charger will deliver depends on what the device negotiates with the host. Look up USB power delivery. There were also older standards for up to 5V/3A or so. Just connecting a DMM across the USB port, or something similar, won't get you the maximum current or power.

I imagine there are devices to test USB power delivery, but I doubt they sell for $10.

--- End quote ---

The host is a Asus Z690-P board, the device is my shiny new Owon VDS1022i usb scope. It needs 5V@2A, and I wouldn't risk damaging it by providing insufficient current...

balnazzar:

--- Quote from: Gyro on October 21, 2022, 12:55:11 pm ---
--- Quote from: alm on October 21, 2022, 12:44:22 pm ---I imagine there are devices to test USB power delivery, but I doubt they sell for $10.

--- End quote ---

Actually I think they do sell for around $10 from China, depending on type.

--- End quote ---

Doh, I discovered they actually sell from amazon at 10$ too.. 24hrs delivery..
I should still establish if these contraptions can damage the usb port, though...

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