How to connect 4-pin Molex to DC barrel plug?

I'm trying to connect a 3.5in SATA HDD that requires 12V power source to my laptop. Because the laptop can't provide 12V I need an independent power source. I already have a 12V power adapter. At the end it has what seems to be called a male dc barrel plug. I'm trying to figure out how to connect it to the 15 SATA power pins. I imagine that buying the SATA to 4-pin Molex simplifies things. So these are my questions:

Can a 4-pin molex be connected to the 12V power source to power the HDD? Is there any intermediary device necessary?
If not, then how should I connect or solder the 4-pin molex to the barrel plug?

Dominykas Mostauskis

Posted 2014-06-05T14:18:41.823

Reputation: 312

Answers

3.5" SATA hard hard drives require both +12 and +5V power sources. You have not mentioned the 5V supply. It will often be more than the 500mA USB connector can supply, even after negotiation over the USB bus for current (which requires a microcomputer for that to happen properly).

It's possible you could dismember a USB cable and wire it and the 12V supply to the Molex, but there are risks if you get the pinout wrong (here you can find the color codes and what the pins do), and if you exceed the 100-500mA the laptop will output on the USB power, the port may shut down or (on very old laptops) you might lose a fuse that requires a lot of work to replace.

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If you get the polarity or the pins wrong you could damage your computer or your disk drive (or both).

One cleaner solution is to simply use a power supply with a +5 and +12V output, such as this one:

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Which comes with a plug that can be mated to a Molex or SATA power connector through an adapter.

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Check your local computer store- they're not expensive. They're part of a kit for USB to SATA/IDE drive.

Spehro Pefhany

Posted 2014-06-05T14:18:41.823

Reputation: 331

This was very helpful. I also found a 4-Pin Molex to 2.1mm DC to be a possible solution to this as well. – user339807 – 2014-06-30T01:50:28.740

2If you cannot find this type of PS, you can use a standard ATX computer power supply, even a cheap one. You'll need to run a wire between the green wire and a black wire on the big connector. – DoxyLover – 2014-06-05T16:30:44.237

The wire @DoxyLover +1 describes is to make the power supply start. Of course the ATX supply will already have the Molex (and maybe SATA) connectors on it. – Spehro Pefhany – 2014-06-05T17:56:58.137

The answer to your first question is that you will need a Molex to SATA power adapter cable. There are many with a quick Google search.

Adding the barrel plug is a different story. I've not seen anything that adapts Molex to 5v barrel. However, I had a similar problem and I basically just jammed a red and black wire into the appropriate sockets on the Molex side and then wired a barrel connector from Radio Shack off the other yielding a SATA and 5v barrel off the same power supply. Useful when you want to hook a SATA or USB HDD to a small 5v board like BeagleBone and don't want to have two PS's to deal with.

Frank Miller

Posted 2014-06-05T14:18:41.823

Reputation: 11