Low voltage on USB port

Posting to share my discovery about the USB port.

I recently plugged in portable hard drive to my VIM3 and it didn’t work as the hard drive was making worrying noise. I put a usb current/voltage meter between the drive and the USB port and it shows the USB port gives out only 4.49V. Not sure if this is normal for a SBC but I believe this under voltage is the raison my portable hard drive didn’t work.

PS. this voltage was enough to drive my NVME to USB adapter though.

Which power adapter are you using to power up. The vim3?

You will need higher amp to support additional usb drive or your drive should come wirh dual usb connection cable to get power from 2 usb.

Try a better power adapter first and report back.

hi, ssd works perfectly for me via usb ports, I use a stock power supply, so this is an individual problem, apparently yes, you have a weak power supply, or features of the SSD drive itself

There is always an obvious drop in voltage when using high current device,
It OHM’s law !!!
If it doesn’t power on just try giving your VIM3 more juice to start with…

the most important thing! I hope you switched your OS from pci-e mode to usb3.0? This is a prerequisite!

I tried all my adapters, and this one is capable to output 5V 3A.
As for the drive, it’s actually not very power hungry. As you can see, it draws only 460mA from my Macbook.

I’m in usb3.0 mode. I think maybe the problem only shows up on external hard drive since my SSD works fine (first picture, SSD working with 4.49V 0.42A). Maybe hard drive needs higher power to startup? The noise I heard sounds like spinning disk.

@Electr1 My power adapter is 5V3A capable. The solution I’m using now is to use a powered usb hub.

this is not enough for vim3, you need 12V 2A

really? With 5V2A I can run stress -c 6 without any issue and my amp meter shows 5.02V 1.55A.

These are vim3 requirements, I think you need to stick with this!

it works in the range you are talking about, but vim3 has completely different scenarios, probably your script requires a different voltage

I’m always wondering if the power adapter can output multiple voltages, which voltage will actually be used?
Mine is 5V3A, 9V2A and 12V1.5A, why doesn’t it give out 12V? With max 1.5A, the maximum power is greater than 5V3A.

@Eurus What is the max power draw of the SSD ?, try running a benchmark related to the hard disk, measure the power while doing that as well…

I’m just talking about vim3 requirements

it’s close to requirements

I think the problem is for the hard drive to start, there maybe a surge at the startup.

Well I’m not very concerned with this, I can just use my powered usb hub and everything will be fine.

how are things with other usb drives?

Yes, at powerup peripherals consume a lot of power, It is better to use those kind of peripherals with external power like a USB hub, please note that Laptops and PCs use much powerful power supplies…

One more thing, I see you are using a M.2 SSD, M.2 SSD can consume almost 7w nominal, in that case 24w power supply is highly recommended, I see you are using Macbook Hub, those connect to 2 USB ports, that gives it much higher power limit…

Look, I seem to understand your problem, it looks like the problem is in the cable that goes from ssd to usb port, in your photo I see a connecting cable

sorry I made a typo…
I mean I was not concerned with the problem :sweat_smile: since I have a working solution

Other usb drives… my thumb drives works fine, usb camera also OK.

@Vladimir.v.v I tried the same cable with ssd and hdd, hdd didn’t work while ssd works.

@Electr1 yeap, I think the lesson here is that SBCs tend to have a weaker power output capacity so it’s always a good idea to use a powered usb hub. And BTW, that Macbook usb hub is actually two separable usb hubs, one connects to their own usb c port on the Mac.

the best solution in my opinion is when the disk goes straight into the prot, without any cables, so you can avoid a lot of losses, this is speed and voltage, etc.

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@Eurus I can recommend you to use this splitter cable, it will provide power and data to the SSD

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