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Measuring max output current of a USB port.
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balnazzar:

--- Quote from: Eraldo on October 21, 2022, 12:57:32 pm ---Just plug it into a phone and see how long it takes to charge it. In my phone 6+ hours means a 5w output and with 2 hour it means 15w.

Or just take a usb cable with wires sticking out of one end and just short it with a multimeter in the Amp range. It won't break anything if you do it quickly (or put a power resistor in series with the multimeter with low enough resistance for 4 or 5 amps to pass just to be safe)

--- End quote ---

That could be a good idea. Let me see if I can find a usb cable useless enough that I can sacrifice it upon the altar of science...

Ok, maybe that's not the best course of action.
alm:

--- Quote from: balnazzar on October 21, 2022, 01:37:50 pm ---
--- 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...

--- End quote ---
Do they really support USB-PD? I think a USB-PD IC from companies like FTDI would already take up a substantial part of that money, although no doubt there's cheaper solutions for sale in China.
balnazzar:

--- Quote from: pcprogrammer on October 21, 2022, 01:08:11 pm ---
--- Quote from: Eraldo on October 21, 2022, 12:57:32 pm ---Or just take a usb cable with wires sticking out of one end and just short it with a multimeter in the Amp range. It won't break anything if you do it quickly (or put a power resistor in series with the multimeter with low enough resistance for 4 or 5 amps to pass just to be safe)

--- End quote ---

Here is some bad advice :palm:

Do not do this unless you know what you can expect. It can either blow something up in your computer or in your multi meter.

When trying something like this always start out with a low current and work your way up, but then still you can blow up something in your computer when it does not have a proper USB power implementation.

--- End quote ---

Ah, mh.

I thought that proper modern mobos from a reputable (so-to-say) brand would have had overcurrent protection o__O
balnazzar:

--- Quote from: Ranayna on October 21, 2022, 01:35:09 pm ---Or, if ASUS cheaped out, gross overloads may even damage the ports, or the controller chip, permanently.

--- End quote ---

Great!  ;D
pcprogrammer:

--- Quote from: balnazzar on October 21, 2022, 01:41:24 pm ---I thought that proper modern mobos from a reputable (so-to-say) brand would have had overcurrent protection o__O

--- End quote ---

Yes, but it could just be a fuse that blows when overloaded. Some will have reset-able fuses, that restore after disconnect. Some will have electronic current regulation.

What kind of cable came with the scope you bought? Back in the days spliced cables were used with an extra USB connector to allow drawing current from two ports. Or does your scope have a separate power input for a power supply?
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