Hi, planning to build a low power NAS style rig in a shuttle case, similar to this, except mine won't have a fancy hotswappable controller, and wondered what the power requirements would be?
Atom based mobo (30-40 watts)
5 x sata HDD (10-15 watts each)
So am I right in saying a 100-120 watt PSU would be okay?
The peak power consumption of that system will most likely be in that 100-120 watt range you listed and will idle at about 60-70 watts. The Atom boards have very little change from load to idle, but most desktop HDDs will draw something in the 5-10 watt range when idle. When picking out a PSU, the general rule is to keep your full-load draw below about 75% of rated capacity and to have the idle draw be at least 20% of rated capacity. Getting a PSU that is rated pretty much at what your system actually can draw full-load leads to shorter PSU life as it is being run at nearly full capacity, but running a large PSU at very low loads is very inefficient. So for you, get one that is between 150 and 250 watts and that will be ideal.
Trying to look around at other mini itx boards but it's hard finding info on how much power they use.
The VIA C7 and Nano mini-ITX boards are fairly similar to the Atom units in power draw. There are some JetWay, Zotac, and Intel mini-ITX units that have standard desktop sockets and chipsets and will have a power draw similar to that of a lower-end micro-ATX board with a similar CPU and chipset.
Also, any alternatives to a pico PSU? Look nice but kinda pricey. =/
I'm not aware of any unless you are up for some mod work. If you are, you could probably modify a standard ATX power supply to act as a large external power brick for your pico-ITX setup. The funny thing about that is the PSU would probably be as large as the entire computer in that case.
The main thing that I would be concerned about is the surge of current with 5 hard drives spinning up simultaneously on power up. Seagate's 7200.12 hard drives are rated for a maximum start up current on the 12V of 2A each for example, which means 24W per drive.
Good point about the rated capacities/efficiency, hadn't considered that!
Lots of mini itx cases like the shuttle cases seem to have half decent small psu's built in, some upto 250w so will probably use that. Should be fine, I have a tiny micro atx build with a small psu that was 275 watt I think and that handled a micro atx 780g board with am2 4600+, dvd drive, 5 hdds and more okay, didn't produce much heat either which was suprising.