Camera USB port: Why Power ON?

Just curious if anyone has the design rational behind this.

I've got my share of USB flash memory devices -- including a SanDisk Cruzer, which is basically a very portable SD card reader -- which simply plug in to a PC are are instantly recognized and accessible as a removeable drive.

So why is it, when applied to digital cameras, the camera's power must be turned on before the flash card is accessible?

In terms of battery life issues, this is stoopid , especially on those cameras with slooow USB 1.1 connections and with 3MB+ average file sizes.

But, as usual, I'm sure there is a good reason. Anyone know it?

(Yes, the easy answer is to use an external card reader, which I do. However, my camera's memory slot is blocked by the tripod shoe, making quick dashes between the tripod and the PC not-so-quick.)

The devices you mentioned were designed to be powered by USB. I doubt that USB is supply the power needed to power the camera.

speede said:

Just curious if anyone has the design rational behind this.

I've got my share of USB flash memory devices -- including a
SanDisk Cruzer, which is basically a very portable SD card reader
-- which simply plug in to a PC are are instantly recognized and
accessible as a removeable drive.

So why is it, when applied to digital cameras, the camera's power
must be turned on before the flash card is accessible?

In terms of battery life issues, this is stoopid , especially on
those cameras with slooow USB 1.1 connections and with 3MB+ average
file sizes.

But, as usual, I'm sure there is a good reason. Anyone know it?

(Yes, the easy answer is to use an external card reader, which I
do. However, my camera's memory slot is blocked by the tripod
shoe, making quick dashes between the tripod and the PC
not-so-quick.)

Click to expand...

Sco77 said:

The devices you mentioned were designed to be powered by USB. I
doubt that USB is supply the power needed to power the camera.

Click to expand...

Powering the camera through the USB interface is not my intent.

All I would want is to read the memory card.

Switching power sources is very easy to design, either with a physical or an electronic switch. If the camera is 'OFF' and USB supplied voltage is detected at the camera's USB/AV port, it is very simple to design a switching circuit that feeds (and communicates with) the memory card directly. Why this is not employed I do not know.

speede said:

Switching power sources is very easy to design, either with a
physical or an electronic switch. If the camera is 'OFF' and USB
supplied voltage is detected at the camera's USB/AV port, it is
very simple to design a switching circuit that feeds (and
communicates with) the memory card directly. Why this is not
employed I do not know.

Click to expand...

If it's so easy, design one yourself. Digicams are designed quickly and outdated even faster. They have little time to worry about esoterics like this. If you don't like the design of your memory card door, complain about that instead.

--
[ e d @ h a l l e y . c c ] http://www.halley.cc/pix/

Ed Halley said:

If it's so easy, design one yourself.

Click to expand...

Oh, you guys are a funny bunch.

Jeesh, ask an legit question around here and this silly nonsense...

Thank Ed, your thoughtful reply has inspired me!

Sco77 answered your question already.

It's just not the answer u wanted. The usb reader is powered by current travelling down the usb cable. Same as the LED light powered in a corded optical mouse.

Cameras are not designed to use the usb cable as a power source. I'm not even sure if the current is strong enough to power the camera (maybe someone can confirm this). And u need power to access the memory card in the camera.

Dennis

speede said:

Ed Halley said:

If it's so easy, design one yourself.

Click to expand...

Oh, you guys are a funny bunch.

Jeesh, ask an legit question around here and this silly nonsense...

Thank Ed, your thoughtful reply has inspired me!

Click to expand...

The CF card is served up by your camera to the remote computer as an MS-DOS file system, and the embedded computer in the camera runs an operating system with the requisite system services. You can read and write to the card only through standard file system operations. The standalone card reader or Cruzer probably has an embedded DOS "dumb" controller chip, something smaller than a computer. One would not put a dumb controller chip in the camera because it would be redundant. Your camera should not be drawing much power, so the impact on your battery life should be minimal. The big battery drains on your camera are the color display, the electromechanicals, and of course, the flash.

Luke

speede said:

Just curious if anyone has the design rational behind this.

I've got my share of USB flash memory devices -- including a
SanDisk Cruzer, which is basically a very portable SD card reader
-- which simply plug in to a PC are are instantly recognized and
accessible as a removeable drive.

So why is it, when applied to digital cameras, the camera's power
must be turned on before the flash card is accessible?

In terms of battery life issues, this is stoopid , especially on
those cameras with slooow USB 1.1 connections and with 3MB+ average
file sizes.

But, as usual, I'm sure there is a good reason. Anyone know it?

(Yes, the easy answer is to use an external card reader, which I
do. However, my camera's memory slot is blocked by the tripod
shoe, making quick dashes between the tripod and the PC
not-so-quick.)

Click to expand...

I think the real answer is, this is the wrong forum to ask this question. Just trying to start a conversation.

Allow me start over by making this as statement instead of a question:

"Wow, the Integrated Circuit used by flash memory readers sure has gotten small.

"Sure would be neat if a digicam manufacturer could incorporate one of these tiny IC's into digital camera design, with an auto-switching circuit designed to run off of a computer's USB power supply.

"In doing so, when USB power is detected at the camera's USB port and the camera's power is switched off, "control" of the flash memory card could be relegated directly to the PC/USB interface, without having to power up the camera and use precious battery power.

"I've seen similar features implemented in MP3 players, PDA's & smartphones to conserve the device's battery power by bypassing the device's electronics and communicating directly with the flash memory. I hope there is no technological hurdle to keep this from digital cameras.

"Seems silly to have to powe up the whole camera just to read the memory card!"

Thanks for everyone's time. Sorry for disturbing you all with my goofy little notion.

Luke Kaven said:

Your camera should not be drawing
much power, so the impact on your battery life should be minimal.
The big battery drains on your camera are the color display, the
electromechanicals, and of course, the flash.

Click to expand...

Thanks Luke. The LCD display was actually powered up on my previous camera, just to display a tiny USB icon in the upper left corner of the screen! But that camera had average files sizes of 1.2MB so transfers were quicker (not to mention the memory card door wasn't blocked).

My new camera averages 3.5MB file sizes, so in theory, the transfer time is 3x as long, which is from where my concern stems. I'll have to look more closely to see if the LCD stays off when I power up for this connection (good bet that it does?).

What you're saying about redundency make sense, especially if the function is built in to the camera's main processor (not a stand-alone circuit).

I appreciate your reply.

It isn't so much of a worry on my D70, because it has the small monochrome LCD on top of the camera, which uses little enough power that Nikon decided to keep it on and displaying the shot counter 24-7, even when the camera is switched off. I've been running on the same charge for two months now, and that includes a few hundred photos. The energy management is pretty good all around.

The transfer rate isn't necessarily constant--depends upon CF internals, and camera-internal interface and drivers. You can get anywhere from 3MB per second to 20MB a second and going up!

Luke

speede said:

Luke Kaven said:

Your camera should not be drawing
much power, so the impact on your battery life should be minimal.
The big battery drains on your camera are the color display, the
electromechanicals, and of course, the flash.

Click to expand...

Thanks Luke. The LCD display was actually powered up on my
previous camera, just to display a tiny USB icon in the upper left
corner of the screen! But that camera had average files sizes of
1.2MB so transfers were quicker (not to mention the memory card
door wasn't blocked).

My new camera averages 3.5MB file sizes, so in theory, the transfer
time is 3x as long, which is from where my concern stems. I'll
have to look more closely to see if the LCD stays off when I power
up for this connection (good bet that it does?).

What you're saying about redundency make sense, especially if the
function is built in to the camera's main processor (not a
stand-alone circuit).

I appreciate your reply.

Click to expand...

I forgot to mention the secondary reason the color LCD came on on my last camera: to advise me that the battery was running out of juice!

But that camera, too, had a black LCD display at the top which would have been better suited for that role.

I dunno, I guess I've become so used to hearing posters and reviewers alike warn to "get an external flash reader or AC power adapter", that I began to think battery power is a universal problem during USB transfers.

Thanks again.

I thought your original post was fine, and I agree with all the technical inovations coming along daily (some useless) you would think usb socket on camera could be fitted with a gate that switched directly to card when usb cable inserted.
Regards
Carl

There are at least two reasons not to use an external card reader.

1) A card reader with a faulty power supply can zap your CF card, and we've had reports of that, as well as reports where we suspect that.
2) Exercising the pins on the CF card/socket moves wears them.

One thing about leaving your CF card in the camera is that the two demonstrably are reliable together.

speede said:

I forgot to mention the secondary reason the color LCD came on on
my last camera: to advise me that the battery was running out of
juice!

But that camera, too, had a black LCD display at the top which
would have been better suited for that role.

I dunno, I guess I've become so used to hearing posters and
reviewers alike warn to "get an external flash reader or AC power
adapter", that I began to think battery power is a universal
problem during USB transfers.

Thanks again.

Click to expand...

Actually, some cams do this. My "walking around" camera is an older Olympus 520Z and it is automatically detected as soon as I attach it to the computer. I think some of the other Oly cams probably do the same, although my A80 (nor my older Toshiba) do this. Also, the Oly is the only one of the three that mounts as a drive; out of the box anyway.

speede said:

Just curious if anyone has the design rational behind this.

I've got my share of USB flash memory devices -- including a
SanDisk Cruzer, which is basically a very portable SD card reader
-- which simply plug in to a PC are are instantly recognized and
accessible as a removeable drive.

So why is it, when applied to digital cameras, the camera's power
must be turned on before the flash card is accessible?

In terms of battery life issues, this is stoopid , especially on
those cameras with slooow USB 1.1 connections and with 3MB+ average
file sizes.

But, as usual, I'm sure there is a good reason. Anyone know it?

(Yes, the easy answer is to use an external card reader, which I
do. However, my camera's memory slot is blocked by the tripod
shoe, making quick dashes between the tripod and the PC
not-so-quick.)

Click to expand...