Raspberry Pi hard drive

[johnbanks]

PeteB ...
Completely agree with you on low impedance USB charging cables.
I make my own using cheap speaker wire (only 2 wires are needed)

[PeteB]

[Grundgütiger]

[PeteB]

I did some quick measurements using an inline USB power/multi-meter, using a WD5000LPVX as an example, but first this...

From StorageReview.com, measurements of a WD5000LPVT, the interesting part is at the end of the article, a bar graph showing power under various conditions.

wd_scorpio_blue_500gb_power_values.png (22.36 KiB) Viewed 1550 times

Full article:


Now, my own measurements (accuracy should be +/- 0.02A or better):

Idle 0.20A, ~1.0W
Read/Write 0.52A, ~2.6W
Startup 0.88A, ~4.4W (significantly more than LPVT version!)

The last reading is the only really bad news. A relatively low-power 7-mm hard drive with a single platter is using 3/4 of the current allowance for all four USB combined.

That probably explains why some typical laptop drives work when powered only from a single RPi USB port, even though it technically exceeds the Raspberry Pi official current allowance by a wide margin, and therefore, not recommended.

Also, when the drive uses the maximum observed current during its startup, the voltage at the USB port drops to about 4.65 V for a short time, which is below the USB spec. This might interfere with the startup of other USB-powered devices such as a WiFi dongle. In other words, it causes a momentary brownout on power up.

With a better power supply (read, NOT a wall-wart), a good cable, and some capacitors for around $2 maybe, I bet the brownout would not happen.

P. (Ohm, ohm on the range.... oh, never mind, )

[Grundgütiger]

I found an article that also explains some of the writings on USB cables for identifying the vein's thickness. Also read the comments. (The cable I'm using to connect the HDD to the Raspberry Pi is very short and quite thick, so I guess the inner values are ok. It doesn't have any of the mentioned writings.)

[ACX]

[PeteB]

[johnbanks]

I've purchased several of these ...



I make up a 2 wire power cable using speaker wire with a male USB at each end and then connect to the RPi via a short (2 or 3 inches) USB female to micro male adaptor cable. Has the advantage that the USB male to female interface can be the power 'switch' which avoids straining the micro socket on the RPi.

[PeteB]

[Grundgütiger]

I'm still waiting for an answer from the "WDLabsAssistants". I asked for more technical details. If there isn't any technical advantage about using the PiDrive with a Raspberry Pi, I guess it's just another marketing thing. If the enclosure they are selling wasn't so ugly I might have just bought the 1TB drive for that reason. But as long as my set-up works, there's no need for a change.