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Home > Archive > alt.certification.a-plus > April 2004 > measuring wattage draw on psu
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measuring wattage draw on psu
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| strand 2004-04-09, 10:24 am |
| say a psu is rated at 300 or 350watts - and there is a floppy, cd, cd-rw,
and 2 hard drives connected - how can I tell what the total draw is - to
avoid overload ?
| |
| hootnholler 2004-04-09, 11:24 am |
| Hi Strand,
This is a question for the ages... but I'll try and shed some light on
this... First, some background on psu's.
A power supply is mainly a transformer (to a degree) and it does vary
greatly on the components inside of 'em. Not sure if you are familiar with
electronic components, but beliieve me when I say that it really does
matter. The first rule of thumb, get a good power supply. I prefer Antec
or Coolermaster, but of course, that varies from person to person. It's
cheap insurance.
Second, most 'prebuilt' systems will have just enough power supply for the
setup when you purchase. Dell, Compaq, HP, etc... are infamous for this.
I have had a ton of calls due to someone adding a hard drive or such, and
then, the thing randomly reboots. This is due to 'power fluctuation'.
There are software programs that claim to be able to tell you, but for the
most part, they are a 'guesstimate'. I have yet to see a software program
accurately rate wattage inside a pc... I'm sure it exists, but not for the
normal consumer.
One quick and dirty way that I like to check is by going into the bios
(assuming that your motherboard has this option..) and check what the
voltages are for +/- 12 VDC and the 3.3/5 VDC rails. If you are above or
under by more than 10%, it's time to swap that power supply.
When building a system, I have a 'rule of thumb' that I go by. This is by
no means accurate, but I like to leave the customer with some breathing
room. Usually, 100 to 150 watts for the cpu (some of the newer ones are
above this...), 50 watts for each drive, including cd/roms, burners, dvds,
etc... and 35 watts for one stick of RAM and 50 for two. This is an
estimate on the safe side, mind you.
Using the above ratings, you are pushing that limit. If it's a good power
supply, from a reputable maker, you're golden. If it's a 'generic' psu (no
fret, used them myself in the past...) definitely check those voltages in
the bios.
Hoot
"strand" <anyone@hotmail.com> wrote in message
news hxdc.11480$BF2.1155825@news20.bellglobal.com...
> say a psu is rated at 300 or 350watts - and there is a floppy, cd, cd-rw,
> and 2 hard drives connected - how can I tell what the total draw is - to
> avoid overload ?
>
>
| |
| strand 2004-04-09, 11:24 am |
| nice comprehensive reply - thanks hootnholler
--
xx
"hootnholler" <nospam@goaway.com> wrote in message
news:bXxdc.54230$z%1.20990@twister.rdc-kc.rr.com...
> Hi Strand,
>
> This is a question for the ages... but I'll try and shed some light on
> this... First, some background on psu's.
>
> A power supply is mainly a transformer (to a degree) and it does vary
> greatly on the components inside of 'em. Not sure if you are familiar
with
> electronic components, but beliieve me when I say that it really does
> matter. The first rule of thumb, get a good power supply. I prefer Antec
> or Coolermaster, but of course, that varies from person to person. It's
> cheap insurance.
>
> Second, most 'prebuilt' systems will have just enough power supply for the
> setup when you purchase. Dell, Compaq, HP, etc... are infamous for this.
> I have had a ton of calls due to someone adding a hard drive or such, and
> then, the thing randomly reboots. This is due to 'power fluctuation'.
>
> There are software programs that claim to be able to tell you, but for the
> most part, they are a 'guesstimate'. I have yet to see a software program
> accurately rate wattage inside a pc... I'm sure it exists, but not for the
> normal consumer.
>
> One quick and dirty way that I like to check is by going into the bios
> (assuming that your motherboard has this option..) and check what the
> voltages are for +/- 12 VDC and the 3.3/5 VDC rails. If you are above or
> under by more than 10%, it's time to swap that power supply.
>
> When building a system, I have a 'rule of thumb' that I go by. This is by
> no means accurate, but I like to leave the customer with some breathing
> room. Usually, 100 to 150 watts for the cpu (some of the newer ones are
> above this...), 50 watts for each drive, including cd/roms, burners, dvds,
> etc... and 35 watts for one stick of RAM and 50 for two. This is an
> estimate on the safe side, mind you.
>
> Using the above ratings, you are pushing that limit. If it's a good power
> supply, from a reputable maker, you're golden. If it's a 'generic' psu
(no
> fret, used them myself in the past...) definitely check those voltages in
> the bios.
>
> Hoot
>
> "strand" <anyone@hotmail.com> wrote in message
> newshxdc.11480$BF2.1155825@news20.bellglobal.com...
cd-rw,[color=blue]
to[color=blue]
>
>
| |
| strand 2004-04-09, 11:24 am |
| just checked my Award Bios and it seems I'm very close to the margin -
+3.3V is running 3.47V and +12V is running 12.40V and -12V is
running -12.33V
--
xx
"hootnholler" <nospam@goaway.com> wrote in message
news:bXxdc.54230$z%1.20990@twister.rdc-kc.rr.com...
> Hi Strand,
>
> This is a question for the ages... but I'll try and shed some light on
> this... First, some background on psu's.
>
> A power supply is mainly a transformer (to a degree) and it does vary
> greatly on the components inside of 'em. Not sure if you are familiar
with
> electronic components, but beliieve me when I say that it really does
> matter. The first rule of thumb, get a good power supply. I prefer Antec
> or Coolermaster, but of course, that varies from person to person. It's
> cheap insurance.
>
> Second, most 'prebuilt' systems will have just enough power supply for the
> setup when you purchase. Dell, Compaq, HP, etc... are infamous for this.
> I have had a ton of calls due to someone adding a hard drive or such, and
> then, the thing randomly reboots. This is due to 'power fluctuation'.
>
> There are software programs that claim to be able to tell you, but for the
> most part, they are a 'guesstimate'. I have yet to see a software program
> accurately rate wattage inside a pc... I'm sure it exists, but not for the
> normal consumer.
>
> One quick and dirty way that I like to check is by going into the bios
> (assuming that your motherboard has this option..) and check what the
> voltages are for +/- 12 VDC and the 3.3/5 VDC rails. If you are above or
> under by more than 10%, it's time to swap that power supply.
>
> When building a system, I have a 'rule of thumb' that I go by. This is by
> no means accurate, but I like to leave the customer with some breathing
> room. Usually, 100 to 150 watts for the cpu (some of the newer ones are
> above this...), 50 watts for each drive, including cd/roms, burners, dvds,
> etc... and 35 watts for one stick of RAM and 50 for two. This is an
> estimate on the safe side, mind you.
>
> Using the above ratings, you are pushing that limit. If it's a good power
> supply, from a reputable maker, you're golden. If it's a 'generic' psu
(no
> fret, used them myself in the past...) definitely check those voltages in
> the bios.
>
> Hoot
>
> "strand" <anyone@hotmail.com> wrote in message
> newshxdc.11480$BF2.1155825@news20.bellglobal.com...
cd-rw,[color=blue]
to[color=blue]
>
>
| |
| Tom MacIntyre 2004-04-09, 1:24 pm |
| On Fri, 9 Apr 2004 10:42:14 -0400, "strand" <anyone@hotmail.com>
wrote:
>just checked my Award Bios and it seems I'm very close to the margin -
>+3.3V is running 3.47V and +12V is running 12.40V and -12V is
>running -12.33V
Those are fine, all around 5%...in answer to your original question,
to determine draw on the secondary side is usually a difficult matter.
It's a bit easier on the primary side.
Hmmm...this prompts the question - is there an inline device that can
be inserted between the PS and the motherboard that will measure the
wattage on all supplies? Is there a market for there to be such a
device...
Tom
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