Quick question: I have a 2 1/2" hard disk in a USB chassis, and want
to power it with an AC adapter. The USB chassis calls for 5 volts, and
my AC adapter has settings for 4.5 or 6 volts. I expect I'll use 4.5
volts. As to amperage, my AC adapter can be set to 100 or 300mA. I see
no amperage recommendations on either the chassis or the drive. Am I
better off setting the AC adapter to 100mA or 300mA?
Background:
I have a car stereo with a USB port. It can (theoretically) read an
entire FAT32 filesystem.
I recently bought a used 40GB drive, and a USB chassis. I found that
the drive would not function in the car unless it was boosted with a
power adapter hung off the cigarette lighter. Now it works fine in the
car. The car AC adapter doesn't have any indication of the amperage
it's putting out.
I am attempting to format this drive fully (I was able to get a quick
format out of it, but not a full format - it kind of 'stopped' after
about 3%).
I'm guessing that it's a power issue again, as I'm just hanging the
drive off the USB port of my home PC, with no external AC.
The chassis unit does include a USB 'Y' cable of sorts, which is
supposed to be used when powering the drive off the port. There seems
to be power enough to allow me to copy files (I've half-filled the
drive in this fashion).
But I do want to do a full format, which seems to fail (and again, I'm
guessing it's because of power issues).
I do have an AC adapter which I can set to 4.5 or 6 volts (the USB
chassis calls for 5 volts). I also have the option of using 100mA or
300mA on the AC adapter. I don't see any specific amperage numbers on
the drive, nor the chassis.
I'm not sure what I should set this AC adapter's amperage to. Any
recommendations?
Re: Power requirements of 2 1/2" laptop hard disks??
BD <robert.drea@gmail.com> wrote:
> Quick question:
This isnt a quick question, its a slow one.
> I have a 2 1/2" hard disk in a USB chassis, and want to power it
> with an AC adapter. The USB chassis calls for 5 volts, and my AC
> adapter has settings for 4.5 or 6 volts. I expect I'll use 4.5 volts.
You should get one with 5 volts.
> As to amperage, my AC adapter can be set to 100 or 300mA.
Unlikely. You sure that isnt just the different current at different voltages ?
> I see no amperage recommendations on either the chassis or the drive.
> Am I better off setting the AC adapter to 100mA or 300mA?
No harm in using the highest current setting if it does actually allow you to set that.
> Background:
> I have a car stereo with a USB port. It can (theoretically) read an
> entire FAT32 filesystem.
> I recently bought a used 40GB drive, and a USB chassis. I found that
> the drive would not function in the car unless it was boosted with a
> power adapter hung off the cigarette lighter. Now it works fine in the
> car. The car AC adapter doesn't have any indication of the amperage
> it's putting out.
Then it should state the power that it can supply in watts.
> I am attempting to format this drive fully (I was able to get a quick
> format out of it, but not a full format - it kind of 'stopped' after about 3%).
> I'm guessing that it's a power issue again, as I'm just hanging
> the drive off the USB port of my home PC, with no external AC.
> The chassis unit does include a USB 'Y' cable of sorts, which
> is supposed to be used when powering the drive off the port.
Yes, because there is a limit to what each port can supply, so
that allows it to be powered from two ports instead of just one.
> There seems to be power enough to allow me to
> copy files (I've half-filled the drive in this fashion).
> But I do want to do a full format, which seems to fail
> (and again, I'm guessing it's because of power issues).
Unlikely.
> I do have an AC adapter which I can set to 4.5 or 6 volts (the USB
> chassis calls for 5 volts). I also have the option of using 100mA or
> 300mA on the AC adapter. I don't see any specific amperage
> numbers on the drive, nor the chassis.
> I'm not sure what I should set this AC adapter's amperage to.
> Any recommendations?
Re: Power requirements of 2 1/2" laptop hard disks??
> > But I do want to do a full format, which seems to fail
> > (and again, I'm guessing it's because of power issues).
>
> Unlikely.
You're right... I created a 5GB partition at the front of the disk,
and then created a second primary with the remaining space (~32GB).
The second partition formatted fully, with no errors - the first
little 5GB one just siezed up the session when I tried to format it.
So I suspect a physical problem with the drive.
Re: Power requirements of 2 1/2" laptop hard disks??
BD wrote:
>>> But I do want to do a full format, which seems to fail
>>> (and again, I'm guessing it's because of power issues).
>> Unlikely.
>
> You're right... I created a 5GB partition at the front of the disk,
> and then created a second primary with the remaining space (~32GB).
> The second partition formatted fully, with no errors - the first
> little 5GB one just siezed up the session when I tried to format it.
> So I suspect a physical problem with the drive.
>
>
>
Your question is like asking, "I have a 6-32 bolt. Should I use
a 4-40 nut or a 8-32 nut?" The answer is, "NEITHER."
And no amount of wishing will make either one work.
And if you try to force it, you're gonna bust the bolt.
Suggest you quit guessing and get some data.
I just picked up a random drive...written right on the label is 5V 0.7A.
I've seen 1.1A 2.5" drives.
If it's not written on the drive, it should be written in the spec at
the vendor website. You'll also find a spec on the voltage allowance.
It's 5V +/- not much.
It's likely that 300MA will NOT run your drive.
Is your power supply regulated? If it's a random older suppply, it
won't be. The voltage numbers are "guidelines" at best.
Drives have WIDELY variable current requirements depending on what
they're doing. Your drive may spin up, but when it tries to seek
and the power supply current limits, it may flail the heads
whoknowswhere trashing your platter.
Then there's the issue of ground loops. If you get disk power ground
from your cigarette lighter and the signal ground from your player, you're
asking for trouble...a LOT of trouble when you start the car or switch
off the lights, honk the horn, or do anything electrical.
Here's the info on that: http://www.littelfuse.com/data/en/Ap...tes/an9312.pdf
And check out the wiring in your drive case. It's not unusual for
the external voltage input to be connected to the usb voltage.
So, with the drive powered, it tries to stuff volts into your player
and vice-versa.
So, it's possible that your drive won't format because you've trashed it
already. And you run the risk of also trashing your player thru the
ground loop and 5V connection.
Bottom line, DON'T DO IT!!! I had the same idea and rejected it on
technical grounds.
It's unlikely that the engineers that designed the player cared much
about what you're trying to do. They were
much more concerned with taking out 0.2-cents of cost.
Get a big thumb drive and reload it when you get bored with the music.
Re: Power requirements of 2 1/2" laptop hard disks??
On Tue, 04 Sep 2007 11:57:20 -0700, BD <robert.drea@gmail.com> put
finger to keyboard and composed:
>Hi, all.
>
>Quick question: I have a 2 1/2" hard disk in a USB chassis, and want
>to power it with an AC adapter. The USB chassis calls for 5 volts, and
>my AC adapter has settings for 4.5 or 6 volts. I expect I'll use 4.5
>volts. As to amperage, my AC adapter can be set to 100 or 300mA. I see
>no amperage recommendations on either the chassis or the drive. Am I
>better off setting the AC adapter to 100mA or 300mA?
>
>
>Background:
>
>I have a car stereo with a USB port. It can (theoretically) read an
>entire FAT32 filesystem.
>
>I recently bought a used 40GB drive, and a USB chassis. I found that
>the drive would not function in the car unless it was boosted with a
>power adapter hung off the cigarette lighter. Now it works fine in the
>car. The car AC adapter doesn't have any indication of the amperage
>it's putting out.
>
>I am attempting to format this drive fully (I was able to get a quick
>format out of it, but not a full format - it kind of 'stopped' after
>about 3%).
>
>I'm guessing that it's a power issue again, as I'm just hanging the
>drive off the USB port of my home PC, with no external AC.
I don't use XP, but I believe the max power consumption of your USB
device will show up in the Power tab in USB Root Hub properties of
Device Manager. Depending on the level of integration in the design,
this figure may reflect the current consumption of the USB controller
in the enclosure rather than the drive, which of course wouldn't help
you much.
There is also a utility called Usbview which should report the power
requirements of attached USB devices.
>The chassis unit does include a USB 'Y' cable of sorts, which is
>supposed to be used when powering the drive off the port. There seems
>to be power enough to allow me to copy files (I've half-filled the
>drive in this fashion).
>
>But I do want to do a full format, which seems to fail (and again, I'm
>guessing it's because of power issues).
Try the HD manufacturer's diagnostic tools. For example, Seagate's
SeaTools and Western Digital's Data LifeGuard both claim to test USB
and Firewire HDs.
>I do have an AC adapter which I can set to 4.5 or 6 volts (the USB
>chassis calls for 5 volts). I also have the option of using 100mA or
>300mA on the AC adapter. I don't see any specific amperage numbers on
>the drive, nor the chassis.
>
>I'm not sure what I should set this AC adapter's amperage to. Any
>recommendations?
>
>Thanks!!
>
>Cheers,
>
>BD
Use a regulated 5VDC adapter, or whatever the enclosure specifies.
AFAIK, some drives can detect when the voltage is too low and will
fail to spin up if this is the case. Some Seagate drives specify a
voltage tolerance of 5V+/-5% which would mean that the minimum
acceptable voltage is 4.75V.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
Re: Power requirements of 2 1/2" laptop hard disks??
BD <robert.drea@gmail.com> wrote:
>>> But I do want to do a full format, which seems to fail
>>> (and again, I'm guessing it's because of power issues).
>>
>> Unlikely.
>
> You're right... I created a 5GB partition at the front of the disk,
> and then created a second primary with the remaining space (~32GB).
> The second partition formatted fully, with no errors - the first
> little 5GB one just siezed up the session when I tried to format it.
> So I suspect a physical problem with the drive.
Yeah, very likely.
I'd personally get a 2.5"/3.5" converter and put it internal so I could
run the hard drive manufacturer's diagnostic on the drive and get a
look at the SMART data with Everest.
Re: Power requirements of 2 1/2" laptop hard disks??
> So, it's possible that your drive won't format because you've trashed it
> already.
That specific possibility is not likely. The formatting failure
occurred before any AC power adapter was introduced. The first thing I
did was to stick the drive in the chassis, plug it into my USB port
with no additional power, and attempt to format it.
As well, since I isolated the first 5GB with an unformatted partition,
the remainder of the disk formatted without errors. It is running fine
in the car, with 16GB of MP3s loaded onto it.
That said, the ground issue is something I had no clue about.
That PDF is way over my head. I think I'll get onto some forums re. my
specific player, and chat up some of the folks who've made this all
work properly - see exactly what bits and pieces they ended up using.
Re: Power requirements of 2 1/2" laptop hard disks??
BD wrote:
>> So, it's possible that your drive won't format because you've trashed it
>> already.
>
> That specific possibility is not likely. The formatting failure
> occurred before any AC power adapter was introduced. The first thing I
> did was to stick the drive in the chassis, plug it into my USB port
> with no additional power, and attempt to format it.
>
> As well, since I isolated the first 5GB with an unformatted partition,
> the remainder of the disk formatted without errors. It is running fine
> in the car, with 16GB of MP3s loaded onto it.
>
> That said, the ground issue is something I had no clue about.
>
> That PDF is way over my head. I think I'll get onto some forums re. my
> specific player, and chat up some of the folks who've made this all
> work properly - see exactly what bits and pieces they ended up using.
>
The message of the ap note is this:
An automotive electrical system has HUGE voltage spikes that WILL
destroy any electronic equipment that is not protected against them.
You obviously can make electronics stuff work in a car, but you gotta
pay attention to the horrible electrical environment and do whatever it
takes to make your system tolerate it. Sticking it into the USB
port of a radio is ill-advised. If I were gonna do it, I'd redesign
the USB power inside the radio so it could run the external drive.
There's also a problem with taking random advice.
Every vehicle is wired differently. People tap off voltage and ground
from different places even with the SAME vehicle. Something as simple
as whether your mounting system is a good ground from electronics
chassis to the vehicle chassis can make a big difference. I'm not
saying that grounding is good. It may be the current path that destroys
your system. Interesting things can happen when two parts of
the same system are on different fuses.
Some people are just plain lucky.
Re: Power requirements of 2 1/2" laptop hard disks??
BD wrote in news:1188968776.741875.112650@d55g2000hsg.googlegr oups.com
> > > But I do want to do a full format, which seems to fail
> > > (and again, I'm guessing it's because of power issues).
> >
> > Unlikely.
>
> You're right... I created a 5GB partition at the front of the disk,
> and then created a second primary with the remaining space (~32GB).
> The second partition formatted fully, with no errors - the first
> little 5GB one just siezed up the session when I tried to format it.
> So I suspect a physical problem with the drive.
No need (thanks) - I went to the vendor, we determined that it was
some bad sectors, I got a different disk, formatted it clean (several
times) and it's working fine.
Power requirements of 2 1/2" laptop hard disks?? 
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