this could be useful for turning an old box w/ crappy PSU into a server with a bunch of disks, but of course, a new PSU wouldn’t be that terribly expensive, compared to the prices of large disks :P

Hey, I like this idea. Although it has pretty limited applications, it would be good to do this in reverse for external HDDs. Mine just has the disk spinning regardless of whether the computer is on or not, but if you were to use some sort of relay like thing you could possibly turn the disk off when not in use.

@Karl Schlosser:
Agreed, stuff like this really *should* be standard with SATA interfaces, but when most systems only have two HDDs it’s not a large concern. Still, would be nice to have…

A great idea. SCSI already being able to do that is even better though.

some motherboards allow this to be set in bios, but it seems extreme when you can get really nice power supplies for next to nothing (ie my 650 watt ultra is like 59 bucks)

cool idea tho

a great idea to add onto an old system that doesn’t have this feature in bios already and why add another psu to the pile when the old one works fine. this simply makes the old one work with a more distributed load… think more tires on a truck to haul more weight even though the gross weight of the vehicle itself is realitively the same as a similar one with fewer tires.

is this really needed since most computers have a delay that waits until the drive is spun up before trying to boot..

also will retry several times.

hi, linux-works, here.

one of the controlling ideas for this was that you often do not have the choice in what PSU comes on your NAS box. home NAS systems often are very low end hardware devices and by low-end I mean cheaply made ;(

I read story after story about this or that PSu blowing. I have a popcorn hour media streamer and even that thing, with NO drives on it, blows its own PSU. adding a drive would only make things worse, I think.

there’s an intel NAS ‘suitcase’ box that also has had some power supply issues reported by users. its a custom PSU and so replacing it is not an easy option.

what IS an easy option is to be more gentle to the PSu at startup. that’s what this board does.

as a side benefit, I threw in a CLI for a management interface. an out-of-band interface or ‘service processor’ (LOL) if you will. after boot you can connect to this simple CLI and turn on/off drives by number or even get their current power status. maybe more things later on. idea here is that you could spin up whole arrays to use them and then spin them down when not needed; or even JBOD singletons.

/bryan

@Skitchin, it really wont save any power at all… it will just reduce the total amount of inrush demanded by the the hard drives at power up by staggering the power up sequence.

basically, when u attach a “cold” hard drive to a powersupply, the hard drive demands a hellacious amount of power while every capacitor on the board gets charged from an empty state, after all the caps are full, it levels out, then starts the motors which draw a decent amount of power also.

this just staggers the inrush demands so that they dont all pile up at once. its like me asking u for a dollar monday – friday, instead of 5 bux on monday, if that makes any sense… your still giving me the same amount of cash (power), just dolled out so it doesnt seem to hurt as bad (crater the PS).

one reason I picked the arduino is that I already have a good library of APIs for it, for measuring analog voltages, talking to port expander chips and so on.

so its very possible that another iteration of this circuit could measure current drawn by the drives and even use that to intelligently stagger spinup (not just time based but current draw based).

also, temperature monitoring can be done. I’ve used cheap lm75a chips on my arduinos to read digital temperatures. I could run a few of those in the case and ‘do things’ if the temp gets too hot.

/bryan

@ /bryan

yea, you could probably just put a low valued series resistor inline with the coil and measure the drop across it to get current. I dont know how well sampling the power busses for sags would work with the arduino, i think the ADC API calls take a long time and you would miss the droops. ur sampling frequency would be too low to catch the power transients. it might be better to use the timer on uC to measure the switching power supply IC’s PWM duty cycles to get an idea of the load :) the timers gonna be HW driven…

Also, props for the first proper use of the Arduino platform I’ve ever seen. For the next iteration, try scaling back to a couple of resistors, caps and transistors, might save some money as well.

I usually hate this all-arduino-mania but I think this is a well suited task for Arduinois.
Good job.

“Seems easier to just buy a good PSU…they’re really not that expensive
Or set it in the BIOS”

again, you totally miss the point. the point is that you often do not get any choice when it comes to pre-built embedded hardware.

stop thinking in terms of BYO PC’s. this is a case where the problem set forces you to live inside the system and make the best of what you have.

if you don’t have this kind of PSU problem, that’s fine; but to invalidate the problem, itself, is just wrong.

@linux-works
What kind of system has the PSU built in?

Anyhow, two things should be mentioned here:

1) larger wattage PSUs use no more energy than lower wattage ones, this is a myth; PSUs that are switching power supplies will only use as much power as is required (if within capabilities).

2) older PSUs, however, tend to be less efficient; So it might still be worthwhile to upgrade.

@CH, the kind of system I’ve seen that have a PSU built-in as standard are basic HTPC & rackmount cases, although neither of those are usually designed/suited to run more than a couple of harddrives.

This kind of project would be ideal for those who want to build their own massive raid arrays with software such as unRAID http://www.lime-technology.com/ that can handle up to 21 drives.

It’s not a pin 11 spinup. Pin 11 is used to signal to the drive that the BIOS will not send a START UNIT command. That happens over the SATA data cable and has nothing to do with pin 11. This behaviour was added because early SATA implementations did not send START UNIT commands and thus boot would stall.

With pin 11 grounded, the standard behaviour is to spin up when a PHY link is established.

Some drives do have jumpers to select staggered spinup, in addition to pin 11.

And yes, any drive that supports power saving should also support staggered spinup. Certainly it is required for many applications.

yay

here’s one design issue I didn’t quite get closure on. I’m curious what you guys think.

right now, the current flows on the normally-open set of contacts. ie, when the relays energize, those are the contacts that gets used and so for the drives to get (and continue getting) power, the relays have to continue getting power and continue to function (work).

this could be a failure mode; but I’m not sure if its worth designing around. relays have anotehr set of contacts and I could switch over to those, along with making the appropriate source code change. while the server is up and running, the relays would be in the ‘relaxed’ state and the connections would be held by the spring tension in the relays, not the coil electro ‘tension’.

one problem with going with that approach is that during the initial power-on, for some short period of time all drives are connected to the 5v and 12v power lines. the system has to QUICKLY act after a power-on (or even during the climb of a power-on) and push down on all relays to stop the loads from appearing to the PSU at startup. this can be done – but… is it worth it?

comments are welcome on the pros/cons of both styles.

@linux-works, could you use power MOSFETs or solid state relays instead?

I think it would be absolutely fine to stick with relays, they’ll probably out-live the drives they give power to.

I can’t see a good use for this for me, but I’m sure someone out there appreciates it.

@linuxworks

Nice project
You can use latching relays and power the whole thing off of the +5V standby supply. It has more than enough capacity to do its normal functions and power the relays.

One thing I have done is use the gray wire on the ATX connector (PWR_OK)to control when the motherboard starts for things like this. The PWR_OK wire stays low until the power supply voltages are where they should be at power on then it goes high. The motherboard will not start until that wire goes TTL high.

When you turn on a pc the voltages automatically go to the drives before the motherboard. I was a tiny bit concerned about this because that means the drives don’t get the opportunity that the motherboard has to wait till the power stabilizes before starting.

By placing a relay in the patch of the PWR_OK wire you can control when the motherboard starts. You can also monitor that signal coming from the power supply to power transistor controlled relays that then switch the power to the +5V and +12V drive connectors. That means the drives stay off till the power has stabilized then turn on. You could even stagger them (I didn’t ) , to spin up one by one.

funny that you mentioned latching relays; I’m working on a project right now (for audio) that uses them and the same basic relay driver chip.

I’m not sure if I can easily find latching relays that carry decent current, are 5v controlled and available at the usual places (mouser, etc) for affordable prices. the ones I used are cheap and easy to find. for my audio project, I’m carrying preamp-level current thru them (its a relay/resistor attenuator) but I can’t use the same relays on this project.

plus, how do you reset the latching relays on an unplanned power-fail? something would have to set them back, quickly, so that when the power comes up next time they are in the ‘open’ state and drives are not power-connected.

the latching relays I used in my audio project were polarity reversing ones (single coil) and they ‘burn’ thru 2 of the ULN driver ports (you basically make a poor man’s h-bridge from using 2 of the ports and feeding each one into the relay end, with some biasing R’s as pullups).

but for this disk drive project, I did want to use somewhat common parts and avoid anything exotic. latchers are sort of in the exotic catagory.

I suppose I could be more convinced if there was a simple, cheap and elegant way to ensure that they are in the open state at power-up time. after that, the cpu and ULN can take care of the rest.

@jproach: “and is only being used when the PC is running”;

my intention is to use this on servers and those can stay up for weeks, months and if your power company is good, years.

I am concerned with how long these relays can reliably stay in the closed/powered state. I just don’t know or have that data. when I run this on my own personal system, I suppose I’ll have some data, then ;)

you also mentioned mosfets. I did think about that. should I seriously go that route? I do like the fact that they will probably be more reliable than mech relays and certainly eat up less power (no coils). their on resistance is nice and low but is there ANY chance they could affect the actual circuit/load? that was my worry. who knows how a mosfet in series will affect some vendor’s drive on the 12 or 5v rails. these aren’t simple light bulbs as loads ;) so I took the very safe route (for now) and went with relays.

I knew of dc solid state relays (SSRs) but they are very very expensive and also more of a specialty part. I can find ac SSRs but finding DC ones is not as easy or cheap. and I’m not sure they would fit in the same kind of form factor that the cheap mech relays took up.

if this was your data, would YOU use mosfets or relays?

@Neil
Latching relays have the benefit of needing no power after they are switched on . So using one like you describe would require power always.

@linux-works
To turn off the relays in a power failure you can use a diode from the pc +5vdc and a supercap or two to the arduino board. The diode will keep the supercap from trying to power the normal +5vdc standby circuits. I have seen 10F@5VDC caps for $1.49 that would have more than enough power to run the arduino and turn off several relays in a power failure. Let the arduino monitor the +5vdc standby wire to determine if a power failure has occurred.

linux-works:
You are correct, I only read the summary, I was unaware there was some management software associated with the project as well. I take back what I had said, and give even more props for an even better use of the Arduino platform, ;).

As for your question regarding Relays vs MOSFETs, I would definitely go with a MOSFET if this was my data. No mechanical wear, cleaner switching, less power, quieter (could be a drawback, however), and not to mention the fact that it is cheaper and will take up much less space.

@linux-works: A relay supplied with its rated voltage, in a reasonable environment, should theoretically last forever. What kills it is switching, contacts can eventually wear away or weld together. But we are talking 500k cycles for yours!

A FET shouldn’t affect the circuit if the on resistance is reasonably low, and it is rated to take the continuous and surge current of the HDD (I have no clue what it is).

Skip the SSRs as they are usually isolated and rated for high voltages. Check out the “MOSFET, Bridge Drivers” section on digikey, I would recommend high-side switching with internal switch.

I too would like to know the answer to NN’s question. How scalable are these?

@fdsa: I think the startup pulse that hes talking about comes from the fact that the pins come up in the wrong state an have to be disabled as soon as the uc starts running.

yes, exactly what I was referring to.