Raspberry Pi hard drive

[Grundgütiger]

I just found a message about a hard drive from Western Digital, specially designed for the Raspberry Pi. It's called the PiDrive and comes in two versions. A small one with 314GB: http://wdlabs.wd.com/products/wd-pidrive-314gb/ and a bigger one with 1TB: http://wdlabs.wd.com/products/wd-pidrive-1tb-kit/. Might be a good solution for storing music in connection with Runeaudio.

...

[PeteB]

I have been looking at that since a few announcements appeared online two days ago. No reviews yet, just announcements.

There are some vague statements that the 314GB version is tweaked to not draw too much power from the Pi USB port. I would hope this means one can use it with just a simple cable, and not the awful octopus rig that WD was selling with the 1T version.

from the WDLabs web site:

Customized HDD power management for use with Raspberry Pi.
The WD PiDrive 314GB has been engineered to draw less power from your Raspberry Pi.

I hope they did NOT cripple a nice 500GB WD Blue drive just for the catchy 3-14 date reference (sigh)!

I wonder if you can reduce the noise from the drive if you put one or two of those ferrite cores on the usb cable...

[popov]

hi

I use an flash dd ... More expensive ..But less noise, and very fast for read and a 2A power is suffisant
The idea of and less expensive disk is interessant.... is was just hoping a heat with a disk not using this .... usb

Regards

[Grundgütiger]

I use just an average external 2,5" 1TB hard drive, USB powered. If you change the config.txt file of the Linux system the Raspberry Pi is able to power the hard drive - if your Raspberry's power supply is strong enough. But maybe the PiDrive somehow has some Raspberry Pi goodies.

[PeteB]

....If you change the config.txt file of the Linux system the Raspberry Pi is able to power the hard drive - if your Raspberry's power supply is strong enough....

That seems iffy given the USB power management in the Pi 2 and later. For example, when I looked at the datasheet for the 500GB WD drive that this is based on, the peak (not average, or typical) current is listed as 1A.

See middle of page 3

http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-771437.pdf

I do not doubt that you CAN use it, but the power draw from the usb port is going to be continuously bouncing (changing) from around 100 mA to potentially 1A, with almost no decoupling capacitors or any kind of filter. So, you are effectively modulating the 5V power supply rail, on a device where I have a DAC attached to the GPIO connector. That can't possibly improve the SNR of the analog output, let along the power supply at a WiFi dongle.

If you have only 0.3 ohms impedance along that path (I measured 0.35 with a uOhm meter once ), the noise will be potentially outside of the 4.75 - 5.25 limits for USB, unless you add capacitors somewhere...

With an external USB DAC I would be more comfortable, with a HAT DAC, not so much.

If you consider the series of impedances from the rotating drive all the way to a wall-wart power supply... Cables and Circuit boards and Connectors, oh my... (to paraphrase Dorothy)

Don't take this as another dire warning against overloading a Pi power supply, I just think it would be nice if someone actually PUBLISHED specs for the WD3140LMCW so we could make up out mind it its worth the price of a steak dinner.

[Grundgütiger]

You need a power supply with at least 2A for USB-powering an external hard drive via the Pi. Works fine here. The Raspberry Pi Foundation suggestes a 2.5A power supply for the new Pi 3 if you want to power a hard drive via the USB bus.

[PeteB]

You need a power supply with at least 2A ...

Agreed, but Impedance (resistance for all practical purposes here) and power supply capacity are two different things.

[Grundgütiger]

Of course, but the Pi still is an experimental computer to give young people an understanding of computers. It's not meant to be an electricity highly stabilized technical piece of hardware. I had a bunch of Cyrus and Naim equipment with extra power supplies. Their huge ring transformators are gorgeous. But last year I switched to digital music files played with a Raspberry Pi, hardware for only 100 Dollars. I know it's not the holy grail of HiFi equipment, but I love it and don't plan to switch back.

[Grundgütiger]

Maybe this is a great market niche you could fill - you seem to have the technical understanding to come out with a highly sophisticated power supply for the Pi.

[PeteB]

Of course, but the Pi still is an experimental computer to give young people an understanding of computers. It's not meant to be an electricity highly stabilized technical piece of hardware. ..... I know it's not the holy grail of HiFi equipment, but I love it and don't plan to switch back.

I agree with you, for the most part. I agree about the cost, almost everything I do these days is on a budget. And, I did not mean to come off as a jerk, sorry about that.

How about this - when I get home, I'll order one of those WD Pi-Day specials, (they are supposed to ship by March 30), and I will make some measurements and compare with another WD drive...

I designed power supplies for a while, both the ultra-clean linear type, and the inexpensive switching type, for data acquisition equipment and industrial applications. Even one or two for diy audio amplifiers. Maybe I will recycle one of those designs for a Pi, but honestly, I don't think there is a market. For audio, a toroidal transformer is hard to beat. Even the inexpensive Talema-type transformers, coupled with a little bridge rectifier, regulator, and a few good caps is hard to match with an off-line switcher. Sadly, you can't make and sell isolated linear supplies for under $10 like wall-warts.

In the meantime, using a short and low impedance USB charging cable, the kind where they publish the wire gauge like some of the IXCC cables on Amazon, will actually help our application more than a 2.5A supply...

Cheers,

P.