Having a wife and daughter resident at home who are both becoming increasingly 'Green', today they presented me with an 'intelligent' six gang surge protected distribution thingy from 'Lakeland' to plug in to my UPS. This switches everything else plugged into the five subordinate sockets once the computer, (plugged into the first socket) has been powered down. At the moment I have my Netgear ADSL router plugged into this thingy, is that OK? Will my router survive being turned on and off when the computer and monitor is? Will it retain its settings, as I can cheat and just not power down my computer, although I might get caught if they spot all the pretty lights on at night! or I can plug the router directly into the UPS.
On Thu, May 17, 2007 at 04:55:35PM +0100, J.R. Seago wrote:
cheat and just not power down my computer, although I might get caught if they spot all the pretty lights on at night! or I can plug the router directly into the UPS.
Just disconnect the leds on the computer or cover over them with masking tape (or similar) on the router ;)
FWIW I'd leave the router always on because I've known power supplies to die when being switched on/off all the time, maybe someone who knows electronics can say why. That and if your isps authentication servers go away then you won't be able to logon which has happened to me a couple of times in the past and it's very annoying.
Adam
FWIW I'd leave the router always on because I've known power supplies
to die when being
switched on/off all the time, maybe someone who knows electronics can
say why.
It's the thermal expansion / contraction which puts stress in the soldered joints / chips etc.
Switch on and it heats up a bit and expands. Switch it off and it cools down and returns to the normal size. Repeat and it stresses all the components. Like you can bend things (ie a used drinks can)several times but do it too many times and it breaks.
HTH Keith
On Fri, 2007-05-18 at 09:41 +0100, keith.jamieson@bt.com wrote:
FWIW I'd leave the router always on because I've known power supplies
to die when being
switched on/off all the time, maybe someone who knows electronics can
say why.
It's the thermal expansion / contraction which puts stress in the soldered joints / chips etc.
Thermal cycling plays a big part in these failures but not generally at the solder joint level. Dry joints are generally formed by either bad soldering technique (or in the case of commercial production a fault on the process line) or by vibration / top heavy components with no other means of support.
It is also possible to get a situation where the energy flowing through the joint is more than should really be allowed for that pad size..although technically this isn't a "dry" joint
The main exception to that would be where screening metalwork is soldered to the PCB...they always crack due to thermal expansion
There are several other reasons why Switch Mode Power Supplies fail after being power cycled.
One is that you get inrush current, for example the mains input of a standard SMPSU is mains almost directly into a bridge rectifier (AC-DC converter) followed by a nice fat smoothing capacitor across the resulting 300V of DC. The cap is "empty" when the device has been left off for a bit and therefore has a low internal resistance. So for the first few milliseconds this circuit is powered you have a low resistance path across the supply (via the Bridge) until the cap has charged.
This same sort of thing happens all around many electrical circuits, generally a lot of them are stressed more at switch on than they will be during their normal operating cycle. So any weakened components are more likely to fail at this point.
Another reason is that SMPSU's have a number of components that are critical only for startup, typically at least one of those is an electrolytic capacitor. Generally in consumer grade equipment they use cheaper parts that are only designed to survive 85C, so in a tiny wall wart with no vents they soon fail.
But because some of these parts sit unused until startup they sit technically faulty but working well until the next time you try and turn them on.
On Fri, May 18, 2007 at 11:02:36AM +0100, Wayne Stallwood wrote:
But because some of these parts sit unused until startup they sit technically faulty but working well until the next time you try and turn them on.
Thanks for those explanations, it probably explains why I saw quite a few netgear psu's fail after power cycling them given they didn't have enough time to cool down before they were powered up again to suffer from thermal expansion problems. I have also known disks to fail when they've been moved from one data center to another, I believe this is to do with lubricants that are only needed to help spin the disk up going bad over time and if you let the disk get cold then the bearings shrink and the motor can't get the disk spinning again (or something)?
Adam
On Fri, 2007-05-18 at 11:25 +0100, Adam Bower wrote:
I have also known disks to fail when they've been moved from one data center to another, I believe this is to do with lubricants that are only needed to help spin the disk up going bad over time and if you let the disk get cold then the bearings shrink and the motor can't get the disk spinning again (or something)?
You get stiction in the platter motor bearings which combined with old lubricant, and worn cold bearings can be too much for the platter motor to overcome. There is a sort of twist/snapping motion that you can do which uses gyroscopic forces to overcome this in extreme circumstances...but essentially a drive doing this has "problems" This is the reason that one of the things SMART monitors is platter spinup time to try and preempt this.
Also the head-platter gap is maintained purely by aerodynamics and the head actually rests on the disk surface when it is stationary. There is a landing zone on the disk for this to happen away from data and the heads don't move from this point until the disk is up to speed. However repeated landings or landings on a contaminated or damaged disk surface can cause problems with the heads.
Desktop/server drives can in some cases have a lower tolerance to this than ones designed for mobile computing. Which is why you should exercise caution when applying drive spin down power management settings to desktop machines. I have seen some desktop drives with a design spin up cycle count of 10'000 events which if you had really aggressive drive spindown times could result in early failure of said drive
I have had problems (with Netgear DG834's specifically) where they seem to suffer problems when only powered occasionally.
A perfect case example is my Girlfriends father who as a Health and Safety Consultant seems to like to unplug everything at night. He has been through a few 834's now and the symptoms in each case seem to revolve around the device not being able to connect when first being powered up.
In short devices like that are designed to be powered up on a 24/7 basis and you may get unexpected results or shortened life if you only power it on demand.
In my household I have fought the green argument several times, usually by one of the following (dubious) arguments
1. Replacing all the lightbulbs in the house with low energy ones, this results in a net energy saving that is more than equal to the energy costs of leaving my equipment powered.
2. Insistence that in some cases power cycling shortens equipment life, in some cases the energy resources that went into the initial production of this equipment can be more than it will consume in it's design lifetime therefore the total energy cost of the equipment is only improved by leaving it powered up.
3. Nearly all of the energy that goes into my computer is turned into heat (ignoring the minimal energy required to keep the fans and hard drive spinning) this in turn means that I have never had to turn the radiator on in my study, which in turn lowers the energy we consume to heat the house. (ok this one is tenuous at best and is a moot point in the summer when I am opening windows to get rid of said heat)
ooh and the best one, my business now operates through SIP phones, my home extension will only work if the router is powered :-)
-
Adam Bower -
J.R. Seago -
keith.jamieson＠bt.com -
Wayne Stallwood