[clug] [Offtopic] Mains voltage fluctuations

Michael Cohen scudette at gmail.com
Tue Sep 2 13:10:05 GMT 2008

  Are you saying that it only ever shuts down during the boot
sequence, but if it makes it past that its solid? That might indicate
that your power supply is unable to deliver the required current. When
the unit boots it tends to use most power and often the embedded micro
will also check the voltage levels so if they are too low it will
refuse to boot the system. Once you get past the initial boot the
voltage may fall much lower with no noticable effect on the system.

You should test the internal DC voltage if you can to ensure its
within specs. Does the unit have an external power pack or is it a
built in power supply? If its external you may be able to run it off a
bench power supply and check its stability when receiving accurate


On Tue, Sep 2, 2008 at 9:19 PM, Peter Barker
<pbarker at barker.dropbear.id.au> wrote:
> On Tue, 2 Sep 2008, Michael Cohen wrote:
>> We have recently used a UPS to monitor the input voltage levels - you
>> can get the ups daemon to make a log file of the input voltage every
>> 30 seconds and this way you have a running tally of how the voltage
> Time for a new UPS, it seems.  My 11-year old-UPS doesn't do much apart from
> report loss-of-power conditions.
> I'm *assuming* that the ones people are using they're using from Linux :) So
> - what are people using for UPSs now-adays?
>> fluctuates during the day. If the voltage is commonly found that the
>> level with no effect on the unit you can deduce that its not sensitive
>> to the voltage levels.
> Hmmm..  You're not the first to mention the possibility of transient line
> problems.  I kind of lean against that theory, as once the unit is running,
> it stays running.  It *may* just be more sensitive when starting up, but the
> transients would need to be pretty frequent to be so reliable about shutting
> it down.  Note again that once it is running, it stays running, so there
> must be *something* in the "more sensitive when starting up" thing.
>> Michael.
> Ta,
> --
> Peter Barker                          |   Programmer,Sysadmin,Geek.
> pbarker at barker.dropbear.id.au         |   You need a bigger hammer.
> :: It's a hack! Expect underscores! - Nigel Williams

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