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Joel's Experiments - NAS


September 2017

After my PC power supply died recently, I decided to look for an alternative to Intel for my home computer to be smaller, cheaper, and consume less power. Obviously I considered some of the recent SBC (single board computers) based on ARM that have come on the market. Unfortunately though, not all of them support SATA, to be able to read my hard disk.

I started to think about what kind of box I could use to build the NAS, and realized that my recently-dead ATX power supply was a perfect candidate!  It is a strong metal box with air holes, and even contains an on/off switch and connector for a power cable. As a result, I decided to see if I could give it new life as a NAS (network attached storage) controller.

ATX power supply

The first step was to open up the ATX power supply, and rip out everything inside. I left the power switch and power connector mounted (as well as the little magnet and the X2 capacitor of course), but everything else came out, including the fan.

I decided to stick with my full size (3.5") SATA hard drive, since that's what I already had. I dry-fitted it, and saw that it would fit only one way in the box, (but it did fit) with barely enough room for the wiring at one end.

Then I had to get a new, smaller power supply to power the drive, that would fit inside the box. According to the manufacturer, the SATA drive requires 2 voltages: 5V and 12V.  If I had gone with an SSD, I probably could have gotten away with a single voltage, but in the end it turned out well for me that I had both of these two voltages available. The power requirements of the drive weren't that high: 0.60A @ 5V and 0.45A @ 12V (peak).  So then it was shopping time to find some candidates.

The power supply I chose is actually powerful enough for two of these drives. I found this one on Ali Express for about $12 - can't beat that.

PS frontPS side

I carefully trimmed the SATA power connectors from the original ATX power supply for reuse.  I figured I would take a double connector since the power supply would support it, and who knows, maybe one day I will swap my one big drive out for two 2.5" smaller ones.

SATA power cable

Then I connected up all the wires to see how the power supply would fit in the box.  Again, it was a tight fit, but just perfect!

PS in box

Originally, I had hope to mount the power supply on top of the drive, to allow for better thermal control. I figured the power supply will generate more heat than the drive, and since heat rises, its better to have the power supply on top. Another reason is that the drive is probably more sensitive to heat than the power supply, and is more likely to be damaged by overheating, so it would be better if the drive were on the bottom.

Unfortunately, it didn't work out that way.  With the positioning of the power connector and on/off switch, there wasn't enough room with the drive at the bottom for the wires to stick out. So I had to compromise by putting the power supply on the bottom, and mounting the drive on top of it.

Now the tricky part.  In order to mount the drive securely on top of the power supply, I needed some more pieces. I grabbed the metal rack meant for holding drives out of an old ATX computer case, and cut it with some tin-snips to fit the power supply on the bottom, while leaving a mounting bracket for the 3.5" drive on the top.

PS with rack for HDD

Now, people with a sharp eye may notice there are some extra wires in the picture above. The orange wire was cut from the SATA power supply cable since it is unneeded in my setup (I think it supplies 3.3V).  Instead, I use it to ground the power supply to the case. The yellow wire provides 12V, which I will use later for the fan, and the red wire provides 5V, which I will later connect to the SBC controller board.  Of course the 12V and 5V both need a ground wire, which are the two black wires. All of these wires are connected to the power supply, alongside the SATA power connector.

Mounting holesNAS controller

I drilled 4 carefully measured holes in the side of the box, and mounted the controller board from the inside of the top of the case on 4 brass stand-offs. The board is an IFC6410 with a Qualcomm APQ8064. This board is too powerful and too expensive for what I need, but since it has the features I require (SATA, Ethernet, fits in the space), and I had one readily available, I used it.  If I ever do version 2, I would like to find another board that is way cheaper ($20-$30 range), has potentially 2 SATA controllers, and foregoes the useless features for this application, such as HDMI and analog audio. USB master is a nice-to-have (this board has 2 of them) but since they are stacked with the Ethernet it really sticks out, and makes placement a challenge.  Also, the positioning of the connector is facing the wrong way for this application, since it must point to the top (or bottom) of the case. If anyone is doing a special-purpose board as a NAS controller, please turn the Ethernet 90 degrees so it faces the same side as the audio (or alternatively make the board 10mm shorter so it can stand on its end inside the case).

Full assembly - v1

Here is a picture of the final assembly - first try. Next steps are to reposition the SBC so the Ethernet is facing down, which will allow for remounting the original fan on top to help keep this assembly cool.