OT SATA HDD voltage requirements

[KernelDebugger]

I'm wiring a toggle switch into the power cable to my SATA HDs. My power
supply runs 5 wires to the hard drive, one is 12v, one is 5v, one is 3v, and
two are ground wires. I don't believe the 3v input is utilized by any of
the SATA hard drives, and that's my question...what is the 3v for? I know
that the HDDs run just fine when using a Molex connector which has only 12v,
5v and two ground wires. If I can skip the 3v feed I can get by with a 3
pole toggle, for 12v, 5v and ground (or the ground could bypass the switch
permitting a 2 pole switch). I've asked Western Digital if the drives use
the 3v input, but didn't get a definitive answer. Anyone know the answer
please?
TIA

 

[Gene E. Bloch]

I'm wiring a toggle switch into the power cable to my SATA HDs. My power
supply runs 5 wires to the hard drive, one is 12v, one is 5v, one is 3v, and
two are ground wires. I don't believe the 3v input is utilized by any of
the SATA hard drives, and that's my question...what is the 3v for? I know
that the HDDs run just fine when using a Molex connector which has only 12v,
5v and two ground wires. If I can skip the 3v feed I can get by with a 3
pole toggle, for 12v, 5v and ground (or the ground could bypass the switch
permitting a 2 pole switch). I've asked Western Digital if the drives use
the 3v input, but didn't get a definitive answer. Anyone know the answer
please?
TIA

I'm just about to shut down, so I'll just suggest that you Google for
SATA specs. Or SATA connector specs.

I'm surprised you're still using the Molex connector instead of the SATA
power connector, but then I have always hated the Molex connectors

 

[Paul]

I'm wiring a toggle switch into the power cable to my SATA HDs. My power
supply runs 5 wires to the hard drive, one is 12v, one is 5v, one is 3v, and
two are ground wires. I don't believe the 3v input is utilized by any of
the SATA hard drives, and that's my question...what is the 3v for? I know
that the HDDs run just fine when using a Molex connector which has only 12v,
5v and two ground wires. If I can skip the 3v feed I can get by with a 3
pole toggle, for 12v, 5v and ground (or the ground could bypass the switch
permitting a 2 pole switch). I've asked Western Digital if the drives use
the 3v input, but didn't get a definitive answer. Anyone know the answer
please?
TIA

The 3.3V rail on a SATA connector, is for the future.

3.3V has been used, but on some rather obscure SSD devices. They might
have been 1.8" SSD drives of some sort (with the micro connector). I
think the manufacturers may have returned to 5V operation, rather than
cause a lot of grief with the 3.3V option. (At least a few people will
be using Molex to SATA power adapters, and those don't have 3.3V. There
are even some cheesy ATX power supplies, where a permanently affixed
SATA cable bundle doesn't have the 3.3V rail hooked up either. There
is no excuse for that, just laziness or super-cheapness, saving one
wire.)

I would use a two pole switch, and just switch +5V and +12V if
it was my drive. The drive has internal transient protection, to
protect from the switching transient of opening the line (a transorb
or the like). We know this, because one USENET poster noticed something
burned on his drive, and he traced down the part number and that was
it's function, transient protection. That is part of the provision for
hot swapping.

There may be a phantom ground connection via the mounting hardware and the chassis
anyway, so opening ground might not float the drive entirely. A quick check
with my ohmmeter shows the grounds on the SATA interface, are common with
the metal body and screws on the chassis. If you're using plastic slides
on the drive, then I suppose that ground connection is broken. I don't
see a particular reason to be disconnecting the ground path.

Paul

 

[Yousuf Khan]

I'm wiring a toggle switch into the power cable to my SATA HDs. My power
supply runs 5 wires to the hard drive, one is 12v, one is 5v, one is 3v, and
two are ground wires. I don't believe the 3v input is utilized by any of
the SATA hard drives, and that's my question...what is the 3v for? I know
that the HDDs run just fine when using a Molex connector which has only 12v,
5v and two ground wires. If I can skip the 3v feed I can get by with a 3
pole toggle, for 12v, 5v and ground (or the ground could bypass the switch
permitting a 2 pole switch). I've asked Western Digital if the drives use
the 3v input, but didn't get a definitive answer. Anyone know the answer
please?
TIA

Most SATA devices are still physically just the old IDE devices with new
connectors on them. As such, they still make use of the 5V and 12V power
rails rather than the 3.3V one. I don't know of any SATA devices that
can use the 3.3V rail, but even if they required one, they could usually
just step the 5V rail down to 3.3V if needed.

Yousuf Khan

 

[KernelDebugger]

I'm just about to shut down, so I'll just suggest that you Google for
SATA specs. Or SATA connector specs.

I'm surprised you're still using the Molex connector instead of the SATA
power connector, but then I have always hated the Molex connectors

Thanks Gene, I've googled myself to death trying to find the answer. As for
Molex,
I only mention that because it shows that the 15 pin Sata power plugs really
have
just four inputs, two of which are ground.

 

[KernelDebugger]

The 3.3V rail on a SATA connector, is for the future.

3.3V has been used, but on some rather obscure SSD devices. They might
have been 1.8" SSD drives of some sort (with the micro connector). I
think the manufacturers may have returned to 5V operation, rather than
cause a lot of grief with the 3.3V option. (At least a few people will
be using Molex to SATA power adapters, and those don't have 3.3V. There
are even some cheesy ATX power supplies, where a permanently affixed
SATA cable bundle doesn't have the 3.3V rail hooked up either. There
is no excuse for that, just laziness or super-cheapness, saving one
wire.)

I would use a two pole switch, and just switch +5V and +12V if
it was my drive. The drive has internal transient protection, to
protect from the switching transient of opening the line (a transorb
or the like). We know this, because one USENET poster noticed something
burned on his drive, and he traced down the part number and that was
it's function, transient protection. That is part of the provision for
hot swapping.

There may be a phantom ground connection via the mounting hardware and the
chassis
anyway, so opening ground might not float the drive entirely. A quick
check
with my ohmmeter shows the grounds on the SATA interface, are common with
the metal body and screws on the chassis. If you're using plastic slides
on the drive, then I suppose that ground connection is broken. I don't
see a particular reason to be disconnecting the ground path.

Paul

Ahso! Thank you very much.

 

[Gene E. Bloch]

Thanks Gene, I've googled myself to death trying to find the answer. As for
Molex,
I only mention that because it shows that the 15 pin Sata power plugs really
have
just four inputs, two of which are ground.

OK - but anyway, it looks like some others chimed in with more useful
information for you

 

[OST]

so sad.. yes it does.. HDD check 3.3V, and send answers "good" (and full lenght manufacturer string) or "fail" (and manufacturer dedicated string and volume 8Gb (NTFS) or 2Gb (FAT-FAT32)).
You have a power supply problem. Hint is two (2) condensators installed between brown and each black wire before molex connector.
I mean brown-black1 and brown black2.
do not worry, modificatiom only for start and spin out that is. no other checks of 3.3V.
solved on dell pe sc440 + WD2500