Odroid HC2 USB HDD

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justtim
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Odroid HC2 USB HDD

Unread post by justtim » Sun Jan 06, 2019 9:21 pm

Hi,

I would like to connect an additional external 2,5" USB 3.0 HDD to the USB port of the HC2 for backup purposes.
The HC2 is currently fitted with a 3,5" 7200 RPM HDD and powered by a 12v/2a power adapter.

Do I need to power my 2,5" external HDD separately to prevent undervoltage, or can the HC2 provide enough power for it?

Is there any way to monitor the device for undervoltage? It is installed with OMV (Debian).

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mad_ady
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Re: Odroid HC2 USB HDD

Unread post by mad_ady » Sun Jan 06, 2019 11:42 pm

2.5" usb hdds should be fine when hooked up to the hc2.

tkaiser
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Re: Odroid HC2 USB HDD

Unread post by tkaiser » Mon Jan 07, 2019 10:26 pm

justtim wrote:
Sun Jan 06, 2019 9:21 pm
The HC2 is currently fitted with a 3,5" 7200 RPM HDD and powered by a 12v/2a power adapter.
Simply do the math: check spinup peak current for this disk in the data sheet (can be up to 2A on the 12V rail alone with some disks), then check spinup peak current of the new USB disk to be attached. Both disks are connected via USB so chances that they start spinning at the same time while booting the HC2 are pretty high.

I've seen external USB3 HDDs drawing as much as 1A@5V when spinning up. So if this external backup disk is not connected all the time but only when needed there shouldn't be any problems but peak spinup consumption could be an issue with permanently attached external disk (this time more an undercurrent issue than undervoltage).

justtim
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Re: Odroid HC2 USB HDD

Unread post by justtim » Tue Jan 08, 2019 3:28 am

tkaiser wrote:
Mon Jan 07, 2019 10:26 pm
Simply do the math: check spinup peak current for this disk in the data sheet (can be up to 2A on the 12V rail alone with some disks), then check spinup peak current of the new USB disk to be attached. Both disks are connected via USB so chances that they start spinning at the same time while booting the HC2 are pretty high.

I've seen external USB3 HDDs drawing as much as 1A@5V when spinning up. So if this external backup disk is not connected all the time but only when needed there shouldn't be any problems but peak spinup consumption could be an issue with permanently attached external disk (this time more an undercurrent issue than undervoltage).
Right, thank you. The 3,5" HDD has a startup value of 2A according to the data sheet. There are no specs available for the external drive, but since it is an USB 3.0 device it can theoretically draw up to 900mA.
The drive is permanently connected. Is there a way to delay the USB HDD startup after boot? Otherwise I could power the USB drive separately which will also deal with the issue.

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Re: Odroid HC2 USB HDD

Unread post by tkaiser » Tue Jan 08, 2019 5:22 pm

justtim wrote:
Tue Jan 08, 2019 3:28 am
Is there a way to delay the USB HDD startup after boot?
No idea unfortunately. And if there's a 'generic' way that will affect all USB drives it's of no use since the 'SATA port' on HC2 is also just a USB drive (minus cabling/connector and USB-to-SATA bridge hassles).

I usually use a rather precise powermeter when doing all sorts of tests and was a little bit scared seeing the HC2 booting up with up to 30W with a 3.5" HDD when testing with early HC2 developer samples over a year ago. Since Hardkernel's PSU is only rated for 12V@2A and the 30W were clearly above this. Turns out the PSU is good for 30W peaks but I would fear the additional 5W a connected USB3 HDD would add.

It might work though but me being an electronics noob fear running devices beyond specs.

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