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hardware question 
12th-Jun-2012 01:50 pm
so I've decided I need a relay. The ideal/stupidest/most-versatile version I can think of would be a power strip that
  • plugs into the wall
  • has one or more outlets on it, and
  • has a USB cable coming out of it
the basic idea being that once I plug the USB cable into my computer, I then have a remote means of turning the strip power on and off.

Embellishments would include being able turn the various outlets on and off separately and the usual array of safety features like having the USB circuit optically isolated, so that if Something Bad happens with the wall power or one of the devices plugged into the strip (develops a short or whatever), nothing bad happens to my computer via the USB line.

I cannot imagine that I'm the first person ever to have thought of this. And, given the vagaries of certain devices I've had to deal with, notably DSL modems, that just periodically need to be power cycled just because, I cannot imagine how any IT shop or network outpost would retain its sanity without something like this to give them the ability to power cycle things remotely.

I know it has to exist. My only worry is that it's so simple it's only available as part of some more complex, hugely expensive thing that I don't need.

So what is it called?
12th-Jun-2012 10:13 pm (UTC)
Doing a google search for "usb controlled power strip" gets me a bunch of results. Are those the sort of thing you're looking for?
12th-Jun-2012 11:09 pm (UTC)
perhaps. I'm now finding a bunch of things that cost around $70, are aimed at Joe Consumer, and all trying to be a little too smart (as in "we'll turn off all of your peripherals for you when your computer shuts down")

I suppose my real question is: What does one actually use in the machine room, when, say, you have a bank of modems, routers, DSLAMS, whatever, that periodically get wedged (*) and you just want to be able to power cycle them remotely. I'm guessing you're not paying $70 per modem. And I'm also guessing you're not soldering your own circuit boards together to attach USB relays to them. That's what I've been finding thus far.

(*) and yes I know they're really not supposed to get wedged, and the Correct thing do is debug them (**) or buy new ones ($), but if they work Well Enough then why bother...

(**) which is kind of hard to do on DSL modems that are basically black boxes and where the problem is just as likely to be at the other end of the phone line anyway
13th-Jun-2012 01:38 am (UTC)
well okay, what I want is to be able to write a perl script that powercycles my DSL modem whenever we detect that port 25 has not received any spam in a while and subsequent pings to a selection of internet sites get no response. Here "powercycle" includes the insertion of a random delay of between 15 and 35 seconds between power off and power on, because apparently these things need it, followed by a 10-15 minute wait period for the DSLAM on the other end to come back from the dead...
... in other words just sufficiently weird that the Joe Consumer device is probably not going to do the Right Thing if all I can tell it to do is "powercycle" or if it insists on following its own watchdog script which is designed around rebooting servers and can't check for the things I want it to

What's annoying is I can do the software part; I just need the stupid device and don't want to spend more money than I have to on somebody else's b0rken UI (and then having to work around it).
13th-Jun-2012 02:39 am (UTC)
hm. much as I hate the idea of doing my own hardware (because I'll get Something Wrong and stuff will catch fire) this

based on this looks pretty dirt simple.

$25 plus enclosure plus the effort of cutting apart an extension cord, slicing one of the wires, and hooking the two ends up to the relay.

so what goes wrong here?

Edited at 2012-06-13 02:46 am (UTC)
13th-Jun-2012 02:43 am (UTC)
What does one actually use in the machine room

something like this.
13th-Jun-2012 03:01 am (UTC)
starting at $549.00 and going up into more digits. Yeah okay. I guess large datacenters have way more budget than I do. Who knew?
12th-Jun-2012 11:16 pm (UTC)
https://www.remotepowerswitch.com/web-remotepowercontrol.html ?

In the labs at Microsoft they were called "DRAC"s -- gave you a web-based interface to all the power supplies in a rack, with an opportunity to power down, power up, or power cycle each port.
13th-Jun-2012 01:12 am (UTC)
Hmm. $190+

Also way too spiffy (http server and password features are massive overkill; I just want to be able to locally say "ON" or "OFF" down a serial line from a perl script... though I suppose a perl script can issue its own GET commands with the security cookies or Authentication: header set correctly, and then parse/screenscrape the responses, but argh...).

DRAC (which Wikipedia tells me is Dell Remote Access Controller) seems to depend on the target machine implementing some particular protocol on its motherboard. No good for controlling a DSL modem.
13th-Jun-2012 02:51 am (UTC)
Two unrelated thoughts:

For “what is it called”, one could look at this as a home automation problem — such systems include computer interfaces. (Perhaps you should ask Kenny!)

The one Thing I Know About That Is Vaguely Relevant is the PowerSwitch Tail which is intended for controlling line-voltage devices from microcontrollers and such; it's basically a relay in a nice box with isolation. (I've never used one and I have no affiliation; I just ran across it in a context now forgotten.) It isn't USB but you could perhaps wire it up to one of the control lines on a serial port or USB-serial adaptor — or a good ol' parallel port if you have one of those.
13th-Jun-2012 03:34 am (UTC)
This could be a job for X10 appliance modules. They have a computer interface called the FireCracker which needs a 9-pin serial port.
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