Power requirements of 2 1/2" laptop hard disks??

[BD]

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.

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?

Thanks!!

Cheers,

BD

 

[Rod Speed]

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?

The 300mA.

 

[BD]

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.

 

[mike]

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/Application_Notes/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.

But that's ole conservative me.
mike

 

[Franc Zabkar]

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

 

[Rod Speed]

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.

 

[BD]

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.

 

[mike]

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.

Three words: big thumb drive
mike

 

[Folkert Rienstra]

BD wrote in news:[email protected]

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.

See if Bart's disktool will run on it.
http://www.nu2.nu/download.php?sFile=diskto12.zip
It's a test and zero write utility in one.

 

[BD]

See if Bart's disktool will run on it.http://www.nu2.nu/download.php?sFile=diskto12.zip

It's a test and zero write utility in one.

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.

 

[BD]

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.

The chassis for the disk included a very oddly designed cable - Mini-
USB at one end (for the drive), USB-A at the other (for the head
unit), and another lead running from the USB-A end of the cable, into
a small coupler, which is USB-A male at one end and USB-A female at
the other. This coupler just hangs there, but you can loop it back
over and stick it on the 'main' USB-A plug. It ends up looking like a
letter 'd', where the stem of the 'd' is the mini-USB end.

The design of this cable appears to be that without the coupler in
place, the cable draws only signal from the port; with the coupler, it
draws power as well. The intent is that if you're using external power
(ie off the lighter), you do NOT use the coupler as well - or you're
pulling power from both ends.

The recommendation from the vendor of the chassis is if I'm intending
to draw power from the USB port, use the coupler. If not, do not use
it.

FWIW - the port on the deck *can* power USB devices - but only up to .
5A, according to the specs. This drive draws 1A.

2 questions, then, since you do appear to feel pretty strongly about
this.

1) What's the worst that could happen? Fry the drive? Fry the head
unit? Blow a fuse? Catch my car on fire? and

2) what process should I follow, with a multimeter or whatever, to
establish that this is a viable arrangement? Since I got the issues
with the physical disk worked out, I see no evidence of any weirdness.
But granted, it hasn't been sitting in there for very long.

I'd far prefer to verify a problem, than just back away from the whole
idea with my hands in the air. I just don't have the education
required.

Thanks!

 

[BD]

The message of the ap note is this:

I just had a (nother) chat with a buddy of mine who used to be an
electrical engineer, and spent years installing high-end car stereos.

His take is that the design of that USB cable on the drive is intended
to pull power only when the little coupler on the end is in use.
Without the coupler, the cable only has connectivity on the data
lines.

He did the same thing (crippling a USB cable by severing its power
leads internally) for a very similar purpose once.

He's going to hand me a small multimeter, just to be sure.

 

[Folkert Rienstra]

BD wrote in news:[email protected]

It's a test and zero write utility in one.

No need (thanks) -

Get it anyway, for the next time.
http://www.nu2.nu/utils/#disktool

I went to the vendor, we determined that it was some bad sectors,

*Unreadable* sectors, they may not actually have been bad and been
the result of low power during your experiments with the car radio.
A zero write would have taken care of them.

I got a different disk, formatted it clean (several times) and it's
working fine.

For now.
If the problem that caused them wasn't really resolved they may return.

 

[mike]

The chassis for the disk included a very oddly designed cable - Mini-
USB at one end (for the drive), USB-A at the other (for the head
unit), and another lead running from the USB-A end of the cable, into
a small coupler, which is USB-A male at one end and USB-A female at
the other. This coupler just hangs there, but you can loop it back
over and stick it on the 'main' USB-A plug. It ends up looking like a
letter 'd', where the stem of the 'd' is the mini-USB end.

The design of this cable appears to be that without the coupler in
place, the cable draws only signal from the port; with the coupler, it
draws power as well. The intent is that if you're using external power
(ie off the lighter), you do NOT use the coupler as well - or you're
pulling power from both ends.

The recommendation from the vendor of the chassis is if I'm intending
to draw power from the USB port, use the coupler. If not, do not use
it.

FWIW - the port on the deck *can* power USB devices - but only up to .
5A, according to the specs. This drive draws 1A.

2 questions, then, since you do appear to feel pretty strongly about
this.

I spent the last 10 years I worked fixing other people's designs.
Problems don't often come from things you think about. They come from
the things you didn't consider.

Say your kid wants a cat. So you ask other people who have cats.
Based on their inputs, you figger it's pretty safe to get a cat.
Most people just ignore the fact that a medium sized cat can shred
your flesh in an instant should she decide to...
So, you get a special deal and get two cats. You watch them carefully
under varying conditions and consider them to be safe.
One day, you come home and the insides of your sofa is all over the
floor. You don't have any direct evidence, but you conclude that
one of the cats must have done it. You can't duplicate the experiment.
Maybe it won't happen again...maybe it will. You may never know that
a dog visited the apartment next door and precipitated the event.
All you really know is that you need a new sofa.

Your car electrical system is much like a cat. Very powerful, complex,
unpredictable, very difficult to instrument. Works well most of the
time. You've read the application note. The environment is horrible.

If you had the schematic for the deck and the wiring diagram for
the vehicle, it would be much easier to predict what might happen.

About the best you can do is follow general engineering principles.
I'd take the ground from the USB plug. I'd take the power off the
inside end of the power filter inside the deck. Next best thing
is to pick the source voltage off the same wire that supplies the deck.
But you have to protect the disk drive source against the transients.
This is often done with the help of a big capacitor. Problem now is
that the cap forces the transient right into your USB ground inside the
deck's transient protection. That's a BAD idea. Ok, so you use a first
stage filter to ground outside the radio and a second stage filter
referenced to the USB ground. That works until you unplug the USB hose.
Now, you need some ground reference inside the disk supply. Catch-22.

And there are other subtle things that can happen. I put an amplifier
on my car radio. Had low level inputs that I was gonna use for my
mp3 player. Worked great until I tried to plug power for the mp3 player
into the cigarette lighter. Then I had all manner of hum, tones, clicks,
pops in the audio. Worst offender was the whine of the dash light
dimmer. If the ground loop is serious enough to hear the dimmer, what
the heck is gonna happen when I start the car?

The amp had differiential inputs and I isolated them with resistors
to prevent worrying about power transients. I wasn't trying to support
high data rate digital signals and power.

The "safe" way to do it is use isolated grounds. Ground the disk drive
to the usb plug and float the 5v supply through an isolated switching
regulator.

But even better is to do what I did. Rethink your requirements.
Next time someone brags that they have 80GB of copyright violation
on their ipod, ask them how many they actually listen to.
My conclusion was that a gigabyte of music was more than I could listen
to. And I can reload it any time. Flash card. Problem solved.

1) What's the worst that could happen? Fry the drive? Fry the head
unit? Blow a fuse? Catch my car on fire? and

Fire is unlikely, but the other is possible. And remember, catastrophic
electrical failure is not your only worry. Your drive has mechanisms
to prevent damage when you power it up/down. But those assume that the
drive's processor is working. If a glitch sends the processor off into
never-never land, your heads are on the fast train to crashville.

2) what process should I follow, with a multimeter or whatever, to
establish that this is a viable arrangement?

You can't learn much with a multimeter. If you can see it on a
multimeter, it's probably too late.
You need a digital storage oscilloscope, good quality differiential
probes, and a lot of time and luck.
A DC current probe can provide additional insight.
You don't have any realistic way of doing margin testing.
Works fine in summer, but in winter the starting current goes up
making a bigger transient that exceeds the protection level.
Or it only fails when the air conditioner kicks on at the same
instant as the turn signal. You can't test every possibility.

If you protect against the hazards in the app note, you're probably
safe.

99% of the people reading this will say that I'm full of it. Just do
it! And they're probably right. Problem with probability is that
it only works for large numbers. When you've only got one and you
have the problem, the probablitiy just went to 100%...for you.
What the heck, worst it can cost you is a drive and a deck.
It's only money. If it works, use it.

Since I got the issues

with the physical disk worked out, I see no evidence of any weirdness.
But granted, it hasn't been sitting in there for very long.

I'd far prefer to verify a problem, than just back away from the whole
idea with my hands in the air. I just don't have the education
required.

I admit that I'm very conservative. Comes from 50 years of experience
busting things. I do have the education. It's all about reward/risk.
I decided that the
alternative was satisfactory at zero risk. Picture me with my hands
in the air listening to a gigabyte of tunes...and smiling because
nobody is gonna break my window to steal the drive not sitting on the seat.
mike

 

[BD]

What the heck, worst it can cost you is a drive and a deck.
It's only money. If it works, use it.

Risk versus reward - I agree. This entire exercise is partly an
experiment. It's not like I dropped a thousand bucks on the system.

I've spoken with several people with decent creds (including the shop
that sold me and installed the stereo), and based on their opinions
(most notable of which is that if I was going to see serious problems
with this arrangement, there'd be *some* evidence of a problem quite
quickly - hums, cracks, etc - of which I hear none), I think that the
risks are as follows, in order of likelihood:

1) I fry the adapter running from the lighter to the drive. Big deal.
20 bucks. I'm currently trying to confirm whether this adapter is
regulated or not.
2) I fry the drive. Bummer, but it's a learning experience. That's why
I bought it used.
3) I fry the head unit. This option seems extremely unlikely.

So I'm gonna do some additional research, including trying to get my
head around the practical recommendations of that technote, to try to
better understand what's happening electrically. But I'm not going to
pull the whole thing out. For me, insisting on zero risk means
tolerating near-zero reward.
If I've properly assessed the risks in this case, I'm willing to
tolerate them.