SATA ground question

[ThatGuyB]

Not sure if this should be its own thread, but I am unable to find anywhere online how one would power a SATA device externally without just using an ATX PSU outside a computer.

tl;dr are the two GND cables going to be bridged in devices, leading to the ground between two separate PSUs with different voltages bridging? And if so, can this cause harm to the 5v PSU?

For those of you who want to read the full story, here are the details (CLICK ME, HERE'S THE SPOT).

As most of you who grew up with ketchup and mustard cables should know, the SATA power connectors have 2x ground cables, 1x 12v cable and 1x 5v cable (+ / - 3.3v that is not needed). As some of you may know, yellow = 12v, red = 5v, orange = 3.3v, black = ground. Order is from right to left: 12v, gnd, 5v, gnd[, 3.3v].

I don’t have a multimeter yet, so I cannot verify myself (going to borrow one when I start my project, I have no use for a multimeter at all times). Online, I can find a lot of diagrams and tutorials on how to wire up SATA and what pin corresponds to what. But nowhere can I find if the two GND pins are actually bridged in devices like SSDs and HDDs.

I am planning to rip a molex end of a molex to sata adapter and wire up the 12v and one GND to a 12v PSU and the 5v and the other GND to a 5v PSU. Well, it will be just a single 19v PSU powering 2 step-down converters to 12v and 5v respectively. The reason I have to resort to this is because the RockPro64 does not allow more than 2 drives connected to the motherboard’s power connector. Supposedly, for SATA, each 5v cable should have at least 1.25A of current.

This answer could help people in general, who don’t want to use a huge desktop psu outside a case to power something like an IcyDock 4x 3.5" hdd bay. And it will definitely help me in trying to wire up 2 PSUs and not to kill myself non-metaphorically.

I kinda understand why Pine64 would not allow running 4 SATA drives in parallel, unless maybe using 2 of their magic splitter cables. I assume the 12v rail is just piggybacked from the 12v barrel jack input, so I wouldn’t worry too much there. What the problem is, is with the RockPro64’s power delivery PCB rail for 5v. The RockPro64 has an inline 12v to 5v step-down converter.

The black heatshrink insulation covers the converters. I don’t know how much power can these provide, but given that I’m planning to use these with 2x IronWolfs and 2x MX500s, I wouldn’t really trust them.

Maybe a case could be made that if I just buy 2x sata splitter to 2 sata connectors and connect on each rail 1 ssd and 1 hdd, it should provide enough amps to power both of them at peak. Do I trust these flimsy things in that scenarios? Well, let’s say Pine64’s track record, as attested by some members of the forum, is not that great. I will still buy from them as long as they make some decent SBCs and other cool gadgets like the Pinecil, but I will be skeptical of their power supplies and things power-related, with maybe the exception being the PinePower (I believe ucav has one that came with a broken display that he fixed himself using a Pinecil, but I could be misremembering).

Another thing about the inline step-down convertors. Mine did not come with the heatshrink properly shrunken. Maybe it is intended, so you can check for disconnected solder points, or maybe they just ran out of hot air to shrink? I don’t know, but either way, I could see the actual soldering job on the cables and I really don’t like how the cables themselves are soldered on the PCB. The PCB itself looks like it was soldered fine, but the cables appear to not be very sturdy, at least to my untrained eye. I’m sure it shouldn’t be a problem unless I’m trying to bungee jump using these as a cord, or if somehow HDDs would fall off from inside the case to the ground and hang onto these solder joints. Both cases, highly improbable, especially once the cables are neatly packed inside the case (don’t get me started on the official case). /rant before I go into other tangents.

[jlittle]

You don’t mention USB at all… USB to SATA cables are common, and originally designed to power 2.5″ drives from USB 2. I imagine with USB 3 a lot of power could be delivered to SATA.

[ThatGuyB]

Not to 3.5" HDDs, these use a lot more power to be powered by USB and external enclosures for these always come with 12v adapters and their own internal power conversion to 5v for the 5v rail.

[xyz]

I do not believe you would cause any issues for the PSU’s if you were to bridge the ground as they should be leading to the same ground which is your homes.(Assuming they were designed properly) What’s the gauge of the wire? If it’s too thin you’ll run the risk of causing a fire. Here is good site with some information A Guide to Wire Gauge Sizes - Precision Manufacturing Company Inc..

Personally I recommend getting an external enclosure with it’s own 12V PSU to avoid any magic smoke or an electrical fire. Best to be safe rather than using some janky cables/setup.

[KleerKut]

The multiple rails of an ATX PSU are exactly the same as what you are doing with 2 buck converters connected to a common power source and ground. The reason they have multiple ground wires on mass produced PSU’s is because it is cheaper to get one size wire (and associated connectors, tooling, etc) and add in multiple wires to increase current carrying capacity. You could always calculate your current draw from the drives and a single conductor of appropriate ampacity.

[ThatGuyB]

Thanks everyone for your replies. Both step-down converters will go to the same 19v PSU, so I think that should be fine.

As for the wiring, I am just using normal PSU cables. I made sure to buy the SATA end-connectors that are less likely to catch fire (yes, it’s a thing, the ones that catch fire the most are the ones that have the cables molded into the plastic casing, the better ones are either the ones that you punch-down the cables into and put a lock-in cover on top, or the ones where the cables are terminated with metal terminals and inserted into the sata connector, that have plastic separators between them).

The total power is 19v 7A, so about 120W give or take. The brick has a thin wire, I am connecting the 5.5 by 2.1 mm barrel jack to a female one with a slightly thicker wire (these I know are 18 AWG), going in parallel in the 2 step-down converters. From there, connecting to the same type of barrel jack cables (male and female) I have, into the sata cables. I believe the SATA cables are also 18 AWG.