USB drives with no phantom load
joeyh.name
joeyh.name
USB hubs with per port power control are the flying unicorn of hardware. Once in a while some vendor slips up and makes one, but by the time people figure it out the vendor has ended the model or replaced it with a different model under the same model number. It’s especially frustrating because many of the USB hub chipsets support the feature, but only if the manufacturer puts a switching transistor on each port. It literally would only cost pennies per port to have the feature.
Found on my phone in 30 seconds. In units of 100k you could easily find something for 2 cents or less.
I'm in the middle of building an enclosure for a cluster of Raspberry PI like boards (~2.4A draw) and want to have software power controls. So I've been looking to do this...
There are specialized devices for this sort of thing from many manufacturers. I'm currently looking at devices from TI - TPS22958. It has a built in charge pump and an R_DS on of 0.014 ohms. So dissipation will be a lot less 0.081W at 12W power delivery, a 0.7% power loss. This of course comes at a cost -- even in the 10,000 of units it will cost ~40 cents a unit.
I've used their products in a variety of automation projects for clients and at home, and have only good things to say.
I happened to have earlier purchased an industrial quality hub that's powered by 12-24V DC, and it turned out to have per-port power control.
Power factor is another concern BTW; I was measuring something like 0.15 power factor when the drive was powered down, and I'm unclear how such a low PF affects inverter efficiency (it probably depends on how good the inverter is). Powering the drives from 12V DC would probably improve their offgrid efficiency.
Getting SMART data from USB drives has been a pain on linux as the kernel rejects SAT ATA pass-through commands & so doesn't work with smartmontools[1].
I have tested across different USB 3.0 drives such as Seagate Backup Plus, MYDIGITALSSD|OTG, SAMSUNG Portable SSD T5 all of which use 'uas' driver under linux & if used with USB 3.0 hub like Tplink USB 3.0 port hub; it bridges using 'hub/4p' driver.
After trying out several other methods in vain, the only tool which I found to be helpful in checking for USB drive health on linux is discscan[2]; which tests for unreadable sectors & latency without using SMART values.
In the rare cases where autodetection did not work, smartctl -d <type> with trial and error works.
Does your drive work in uas mode?
> I'm fairly addicted to that point in development of a project where it's all about exploring a vast solution space, and making countless little choices that will hopefully add up to something coherent and well thought out and useful. Or might fail gloriously.