Powering multiple external HDDs

[IgorM]

I want to add another external usb HDD to my orange pi pc plus mini "server" but I'm having some issues. When I plug in the second HDD the first one gets unmounted or it starts powering on and off. I tried to use a atx power supply to power it via gpio, but it didn't work even with a single drive. What are my options? 

[BaneOfKnoll]

You could re-wire the USB cable to splice in an external USB Power Adapter

Could work, But it might be a bit dodgy.

 

EDIT: clarity. 

[Acedia]

Are those 2,5'' or 3,5'' HDDs?

[BaneOfKnoll]

12 hours ago, James Evens said:

@TopHatTom ground/shielding isn't necessary for high speed datalines ^^

Huh?? I never mentioned grounding/shielding. I just did the diagram in paint... 

 

I found a similar diagram on the old google.

 

 

[bob345]

14 hours ago, James Evens said:

@TopHatTom ground/shielding isn't necessary for high speed datalines ^^

That is completely false. Without a common return there is no reference for the data line between the two devices. You also need to make sure you are using a proper cable and not just long wires as you need to maintain a characteristic impedance of 90 ohms. Without proper shielding or a properly design cable reflections will become bad enough to make the signal unusable.

 

 

[IgorM]

23 hours ago, Acedia said:

Are those 2,5'' or 3,5'' HDDs?

2,5''

[Acedia]

I assume the raspi doesn't provide enough power to power both drives at the same time. I think something like this would solve the issue:

https://www.amazon.com/Unitek-Adapter-Converter-Optical-Support/dp/B00GLL41MA/ref=sr_1_3?crid=7LI33JTJNI50&keywords=powered+sata+to+usb&qid=1553194591&s=gateway&sprefix=powered+sata+%2Caps%2C348&sr=8-3