I'm building a NAS using an ARM board with PCIe (NanoPI M4v2) for domestic use. My goal is to use 12 x 3.5" HDDs that are currently connected to the same ARM board using cheap SATA to USB adapters.
I don't need to have all HDDs always ON so I was thinking about using an Arduino and some 2N222 or TIP220 transistors I already own to switch the hard drives power lines. My idea was to use a low side circuit like this:
Now, my considerations:
- I like the idea of using a low side because hard drives require both 12v and 5v power, however their ground is shared - meaning I can toggle one ground wire per HDD instead of having to deal with 2 power lines;
- I dislike the idea of using a low side because ground / the collector might be slightly above 0v... and HDDs are sensible electronics;
- Relay boards from eBay with transistors and optocouplers might be a solution, however they're more expensive than what I already own and they consume more power. I would really like to have something that I can have between 2 and 4 disk always online and the rest powered off until they're needed.
Does anyone have some tips for me? Have done this / thinks my idea is unsafe?