SATA power for embedded widgets

[...]

Theo,

I'm not completely clear on what you need in the way of connections to the power supply (how is "only get one per PSU" a problem?), but an ATX supply plus this item:

will give you -12V, 3.3V, 5V and 12V via binding posts.

Hope it helps...

Frank

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You mean like a Molex 67926-0021? Or am I misunderstanding you?

Yes , see links below. (Not in the UK though)

If you are willing to cut the connectors that came with the PS, you have endless choices.

--
Roberto Waltman 

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That's a female connector (the bit that goes on the cable). I'm looking for the bit that goes on the PCB.

Theo

Those aren't quite right, but it reminds me there are such things as SATA power splitters which have male power connectors on the 'input' side. Trouble is, they tend to be in-line rather than PCB mount. For example:

Indeed, but that's not that useful if you want to give your widget to somebody else.

Theo

Let's say you want to power multiple boards. They might be clones of the same board, or all different (think rackmount card cage). Imagine the boards take 3.3V @ 4A, 5V @ 1.5A, 12V @ 3A (made up numbers). That's about

60W, which is well into SMPSU territory, and you don't really want to add a 60W PSU to every board so they can run off a single voltage, or a separate power brick for each board. 600W ATX PSUs are cheap, and even allowing for lies in the specs you can still power 5 or more of these boards. They come with strings of SATA connectors so that you can plug several boards into a string (assuming it isn't overloaded). Also, you can easily test, develop and distribute these boards to others - all they need is a simple PC PSU and they're good to go. You can mount these boards in PC cases - if you get the board layout right you can even use existing drive bays/backplanes/etc.

So SATA is a really nice ecosystem for getting multi-voltages out of a commodity power supply. However it turns out that it's also lumbered with SATA signalling connectors, which isn't always what you want.

At 1.25A, which is a bit of a waste of a 600W PSU.

Theo

Ooooo-kay. So your concern is connector standardization both for the PSU _and_ for your "widget" boards. Got it.

Yabbut... the limitation is due to polyfuses, which could be bypassed.

If that were the only problem, you could download the schematic and Gerber files and cut some new almost-alike PCBs sans polyfuses. However, based on your comments above, that still leaves the board with binding posts which you'd then need to connect to your boards. Given that, I see why putting SATA connectors on your "widget" boards is a better solution.

As to the SATA "signalling connectors": If you don't like the standard ones coming off the PSU, what would you prefer to have on your PCBs? I suppose you could put a 24-pin ATX connector on each instead, but I suspect that those would be a bit large.

Ah, well.

Frank

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This?

You'd probably have to find a local distributor.

That's just the ticket, thanks.

Theo

Part of this is I really dislike hand-crimping Mini Fit connectors, which is what I'd need to do to make a 'special' wiring loom (eg 24w ATX to umpteen arbitrary-Mini-Fit connectors). Obviously not a problem if you're making vast numbers and can order the looms in volume, but more of an issue for small volumes. And why crimp if you can use the existing connectors?

Sorry, I should have been clearer. More SATA male connectors are 22 way: 15 way part for power (3 rails * 3 pins each, 5 grounds, 1 reserved) and 7 way part for data (2 twisted pairs, 3 grounds).

The PSU has 15 way connectors in the wiring loom. These plug into the HDD, and a separate cable from the motherboard goes to the 7 way data connector. If they're in drive bays, the drive mates directly with a 22 way connector on the backplane that provides both parts.

So this means that any male connector has the data part included. That means there's a tempting SATA data socket that you just know users are going to try to plug into their motherboard, even if you don't speak SATA signalling at all. It also wastes footprint on the board which you could use for something else.

Hence the idea to just have the 15 way power part on the PCB to receive a cable from the PSU, and no need for the 7 way data part.

Theo

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You didn't really say how many of these you need, but if it's more than a f ew I would consider doing a simple power distribution board taking in the A TX, fusing for your slave boards, and then breaking out to a connector that you like or a set of screw terminals. You can also do a low voltage power on switch and power indicator on there.