[Asterisk-Users] IAXy Power in Australia?

[Roy Eddleston]

> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-
> bounces at lists.digium.com] On Behalf Of Duane
> Sent: 29 August 2004 11:29
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] IAXy Power in Australia?
> 
> Roy Eddleston wrote:
> > Jeremy
> >
> > Don't bother looking for a PSU with a lower current rating,  The
IAXy
> > like any electrical device is designed to run at a particular
voltage
> > and consumes a certain amount of power (W) at that voltage.
> 
> My comment was based on opinions of others that have posted to this
list
> stating the PSU that shipped was 900mA or was it only 800... in any
case
> most devices are rated with a maximum amount of amp needed, not the
> minimum, devices usually don't draw a constant amount of amp, it
varies
> depending if it's actually doing work or not, and since most of the
time
> this device will most likely be idle (ie not in a phone call) it's
> unlikely to draw the maximum current most of the time...
> 
> On the other hand if the device design has changed and the requirement
> for current has also change then it's possible later models won't
> require the same amount of amps, this can be due to refinement of
design
> to be more efficient and require less power or any other number of
> reasons...
> 

Duane

My post was directed at Jeremy to save him wasting his time replacing
his 1500mA PSU with one of a lower current rating, but since you've
replied quoting one paragraph out of context it warrants a reply so
there is no confusion.

I agree that devices are generally rated with the maximum current they
require, plus a margin for safety, I never said they didn't. 

I also agree that the current drawn by the IAXy will vary (potentially
up to it's maximum rating) depending on what it is doing at the time and
whether an attached phone is off hook, ringing etc, again I never said
it wouldn't.

If you read the whole text of my post it is based on
electrical/electronic principals for devices in general not just the
IAXy although it makes no difference.

You're also correct that if the design of the IAXy has changed it may
have a lower maximum current REQUIREMENT or indeed a higher one, I said
that in the second paragraph of my post.

However your comment "Have you tried feeding it less amps at all" is
impossible to achieve unless the PSU concerned is underrated and
incapable of supplying sufficient current to the device at the rated
voltage, in which case the PSU would then overheat and its output
voltage drop therefore resulting in potentially early failure of the PSU
and instability or failure in the device connected to it. 

This misled Jeremy into thinking purchasing a PSU with a lower current
rating would achieve anything, his PSU is a 1500mA unit which is rated
correctly according to the manufactures specification and will provide
whatever current is needed up to and including 1500mA depending on
whether that 1500mA rating is a constant current rating or based on a
specific duty cycle, but that's another ballgame that I am not going to
discuss here.  

You can not feed a device less current, a device will DRAW whatever
current it needs depending on the supplied voltage and the resistance of
its internal circuits or other circuits attached to it, the only thing
that matters is that the PSU or device supplying that current is capable
of supplying the maximum current the attached device will draw.

So as I stated in my previous post, if the IAXy or any other device
requires a current of say 800mA for example, it does not matter whether
the PSU or device supplying that current is capable of supplying 800mA
or 100,000A, the device will still only draw the 800mA it needs and no
more, you can not "feed it less".

OHM's LAW is still a wonderful thing ;)

Cheers!

Roy...