Description

This article is from the CD-Recordable FAQ, by Andy McFadden (fadden@fadden.com) with numerous contributions by others.

5-26] How much power does a CD recorder use?

(2003/04/12)

About the same as a CD-ROM drive, even when recording. Some simple
experiments suggest that the only significant power drain occurs when
the disc is spinning up. Some personal notes follow.


I connected an external Plexwriter 8/20 through a "Watts Up?" power meter.
The Watts Up? device is designed for moderate loads (20W up to about 1700W)
and isn't good at detecting small fluctuations, but it's accurate enough
for this purpose. I connected the CD recorder and a fan drawing 50W
through the meter, and subtracted 50W from the results.

When completely idle, the CD recorder and its power supply draw 8-9W.
Since the recorder isn't actually doing anything, I'm guessing most of
this is loss in the power supply itself. In any event, it establishes an
idle-load baseline.

While playing an audio CD through the front panel headphone jack at 1X,
there was no change in power usage.

While playing an audio CD through Windows Media Player, the load increased
to 9-10W. I got a similar drain while extracting audio at 8x with jitter
correction and at 20x without jitter correction (about 13x actual speed,
according to Nero). Recording a disc at 8x gave the same result.

The only time I saw the recorder draw more than 10W (1-2W above idle)
was during transitions. Inserting an audio CD gave a quick 16W pulse, and
there were similar small blips at the start and end of recording the CD.
Spinning up the spindle appears to draw an extra 6-7W over the idle load,
but very briefly.

A drive with a higher speed rating would draw more power while spinning
up, but would probably use the same amount while actually doing work.
While installing Linux on a different system with an Asus 52x CD-ROM drive,
I noticed the load for the entire system went from around 50W when idle to
a fairly stable 90W while doing CD media verification. How much of that
was the drive and how much was the CPU is unclear -- the load on the system
would go from 50W to 70W when quickly raising and lowering a window under
X11 -- but it's clear that there's more to the story than the drive itself.

My earlier hypothesis -- that CD recorders draw significantly more power
when recording -- appears to be incorrect. There have been cases where
people could do test writes but not actual writes, and solved the problem
by upgrading their power supply. However, this appears to have more to
do with the power supply's stability than changing load requirements.
The power supply that fixed the problem may have been more reliable, or
perhaps the old one was always overtaxed and the problem didn't manifest
itself until something requiring precise power management was in use.

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