Instructables

A USB Power Controled Plug Strip. With Isolation.

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The whole point of this Instructable was to allow me to power on all the accessories for my computer without thinking about it. And then not power all the little power vampire wall warts when I am not using the computer. The idea is simple, you power on your CPU, all of the other parts of the system power up (monitor, laser printer, speakers, etc) When you power off your CPU, they follow suit.Now there products out there that will do this for you, and if you do not have the experience working with line voltage electricity, please stop reading and just go buy one. There are several products that do exactly what we are trying to do here, but of all the ones that I have reviewed have disadvantages over the device that we are going to build. They fall into three basic types:

There are cheap usb controlled power strips, but I have seen several that do not offer any isolation, and if you are creating a possible path for line voltage (120v here in the USA) to your mother board, and its many hundred dollars worth of over-clocked goodness. I would like some isolation.

There are current sensing power strips, One of the outlets is set up to sense current flow. When this happens the electronics in the power strip power on the other outlets. Its a good idea, but sometimes they do not sense correctly, and will not turn on the accesories. Also the electronics require yet another little power supply to be on 24/7, this we are trying to avoid.

There are well designed enterprise grade solutions with isolation, that work very well and have a very hefty price tag as well.

This circuit uses no extra power when it is not in use, and offers some hefty isolation from power surges, and does not cost a fortune to build.
 
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Joel H4 months ago

I have used a similar approach which also works when my computer is in "suspend mode". So when my computer suspends my reciever also shuts down since its connected to the relay. Instead of hooking the relay directly to the usb-port its wired to a "USB To TTL / COM Converter Module" which has pins for suspend mode. The module is about 3 dollar on ebay

http://www.ebay.com/itm/NEW-USB-To-TTL-COM-Convert...

When1 year ago
Thanks for this. If you wanted to use two independent sources to control the power strip, what would be a proper way to do this? In other words, two USB inputs from two computers so that whichever computer happens to be in use controls the power strip. How would you isolate (if that's the right word here) the two 5V inputs from each other? Thanks for any help.
globrite1 year ago
A nice and safe alternative is to use a Wattstopper power unit which is UL approved, has zero voltage switching and as a bonus has DC output at about 150 mA to power your controller. One such unit (B-120 EP) is available from Amazon for about $15. - Enjoy.
mantasxxi1 year ago
Hi lads,have read all this,i know is such of old thread,but like to ask how these tvss diodes working? How its proctecting circuit and blows the fuses? And why there are two of these on each side of fuses? Thanks
toymotorhead (author)  mantasxxi1 year ago
Ok, TVSS diodes are are also known as avalanche diodes. Under normal operation they do not conduct. When the voltage rises to a designated amount they begin conducting. So in this case we are using 7.4 VDC diodes, in a circuit tht is powered by USB power at 5 VDC. So as long as the voltage does not rise above 7.4 VDC they do nothing. If the voltage does rise above that, they begin conducting. This will overload the fuses, and make them fail open, disconnecting the two sides of the circuit.

Its probably a bit of overkill in this circuit as the solid state relay already has quite a bit of isolation built in. But its a second line of defense, which is good, as computers are quite expensive.
sorry once again for my silly questions,but is this protection in case relay fail and starts give an AC power to pc usb port? is this possible? can't understand why should be another reason that usb power should rise above normal 5V?
tell me,can be used one diode and one fuse? or this won't work? is the zener diode will do the same thing as these tvs ones?
nickroche1 year ago
Hey Richard,
This type of project is always going to draw comment from 'concerned people' and I have to admit doing a little data sheet checking myself when I first read it. Of course, people will come up with dozens of ways in which you should have made it safer or with more isolation etc, but I reckon this design is a good balance between isolation, function, safety and cost - there will always be tradeoffs and other ways to achieve the same thing or make improvements. UL, CE, EN standards, isolation transformers, circuit breakers.....hey, what about some thermal fuses in case things run away, or some fuses for the fuses, just in case they don't work?! There is always a 'whats reasonable' line and I'm sure you're well within it, especially for a non commercial, DIY project.
Anyway - good instructible, well made and I like it. Nick
i made this and i found a relay that was 40 amps i think but witch way do you install the diodes silver or black side facing + or -
this is pretty cool but where can you get a relay that is 30 amps
toymotorhead (author)  crazy-blender2 years ago
You can find solid state relays that will switch 30A with ease. The one chosen was selected for its low cost, and small size You can look up the OPTO22 120D45 http://www.opto22.com/site/pr_details.aspx?cid=3&item=120D4

Its a larger form factor part, and is rated up to 45A. At those levels of power you are definitely going to need a heatsink, and you should do a little experimenting to make sure its large enough to handle the heat dissipation, or check with the manufacturer of the device you are using to make sure you have a large enough heatsink, or what they recommend. If you don't, if you are lucky, you will just make your device fail prematurely, if you are unlucky, you could cause a fire.
do you need the heat sink and what would happen if you didn't use it ?
jlongton3 years ago
I just gathered all the components to build a similar device when i realized that the +5vdc delivered to the USB port remains on when in standby mode. I have an HTPC that I connect to my TV. I rarely turn it off. Instead I use a wireless mouse and keyboard to put it in and out of standby. I would like to be able to turn off the peripherals when in standby. It seems like I might have to connect to a 5v power supply plug inside the PC instead. anyone know of a better solution?
toymotorhead (author)  jlongton3 years ago
I can think a few possible fairly simple workarounds to try.

1) Check read up on the motherboard in your HTPC. On some motherboards the USB power can be selected either with jumpers on the Mainboard, or in BIOS as to weather they have power when shutdown or in standby.

2) If you have the room you can install a cheepo PCI USB interface, that should power down when you go to standby, you don't need anything fancy, I would suggest eBay.

3) Check if your power supply powers down the +5v supply to the diskdrives when it goes into standby, the red wire is +5V and the Black is ground. There are usually a couple of extra connectors available.
thanks for the suggestions.

1) I need to have at least 1 port powered while on standby to wake it with my wireless keyboard. so this likely won't work, unless there is a separate jumper for front and rear ports.

2) This is a possibility. If i can find a cheap one, and nothing else works, I might do this.

3) This is another possibility, but requires a bit more work and makes it more permanent to this PC.

It would be nice to have an outlet on the box you made where the PC could be plugged in. Then when the PC was turned on or woken up it would trigger the relay to turn on the strip. I'm not sure how the relay would be triggered though. it would have to detect the current or something,
abishur3 years ago
Wow so you made this a pretty long time ago, but I used this as a basis for my own USB activate power outlet. I needed a single outlet rather than full strip (and I don't really have room for a full strip), but it's still a really great instructable! I did forgo the extra isolation as optical isolation is pretty "fool-proof" so there's (practically) no risk of it jumping back down the USB line and my deal plugs into a surge protector so there's the AC line is also protected from surge back.

Thanks again! Without this guide I definitely wouldn't have had the courage to set up my own system and would have ended up shelling out $30+ bucks for a pre-made "smart" power strip
nickboy983 years ago
pretty good, a good use for this would be in a caravan, buy one of those usb smoke lighter thingy's and you could power a whole caravan with 5 volts of power, even one of those usb solar thingys power an entire caravan with tiny solar power
no mate this just turns on whatever you have plugged into the strip when you turn your pc on like an automatic switch
it dosent make the power from the usb
usb is is only 500ma so you would get virtually nothing if you converted it to mains (you might be able to power a tinny tinny light bulb)
and if you plugged a tiny solar cell into an inverter (a box that makes mains ac from a dc supply ) nothing would happen because its tinny.
you can convert a 9v battery to give you 100,000v but you wouldn't be able to replace a power station with a 9v battery because the output is very small
krisumsnz3 years ago
Hey Rich
Far to much negative comment above! I built this device. Now my HTPC client running mediaportal has a single "on" button - the amp, TV, subwoofer and remote controller power up. Wife and kids happy.
To finish up the whole shebang shuts down with no activity detected with "amp WinOff" and so when a song, DVD etc ends the whole lots switches off again.....(or the off button is used....)
It is fantastic and was simple enough to make

Thanks so much for the idea!
regards
Neville
BigD1456 years ago
Nice instructable, but your computer IS a vampiric wall wart. I just put my computer and peripherals on a single control strip.
Nicer computers and most power supplies (like the Thermaltake Toughpower I used) in DIY computers have a switch on the back of the PSU that's connected into the line voltage. When that switch is off, there truly is no power draw. Therefore, there is no power draw anywhere in the computer or power strip.
Now you're talking about a rocker switch, exactly like what's on a power strip. We're back to just using a single power strip and one switch to do the job.
You're right, but I was thinking more of convenience - the computer is more likely to be closer to you than the power strip than the USB it's plugged into. Also, it would be safer to use multiple USB controlled power strips form one computer power switch, than plug multiple strips into one main strip. You are likely to overload the main strip whereas multiple strips can be plugged into different outlets, and still be controlled by the computer.
This entire project involves a single power strip, so let's stick to that. If you can overload a power strip, you're not really interested in saving power.
It would usually take something like a small welder to blow a power strip
I have blown them before... its a bit easier than you would think. I was running 7 computers (300w x3, 600w x2, 450w x2) and it completely fried the unit. Luckily I had others around. I do computer repair and I have had up to 18 computers running in my workshop at once lol (obviously not all on one strip!).
There's a small amount of power that gets supplied to the mobo to do things like network booting. You can actually boot a room full of computers by sending a special packet to an off computer. All in all this has saved the world gobs of energy because backup computers can be booted remotely, and they don't have to run 24/7 just in case the primary breaks. in this case one little parasitic load can switch off a few wall warts
just checked and the PC seems to be pulling 2 watts. that works out, at 15 cents per KWH as:

(2 * 24 * 365 * .15) / 1000 = $2.63/year

17.52 KWH/year (four loads of laundry in an electric dryer)

I believe that is quite a few wall warts worth of idle juice. Still, it's a pain to shutdown your PC and then flip a switch on a power strip
If you're using tons of USB peripherals, you're probably not going to need them from a remote location. That USB scanner won't do you much good from across the country. Network booting won't even enter into this. Rooms full of computers tend to be either full on or in standby mode. There aren't too many businesses that do a full overnight shutdown or that use a single power strip. Employees rarely even turn monitors off. I can't even tell you how many offices I've walked into that had the same screensaver on every monitor. They stay on all night long and waste vast amounts of power. This entire project is tailored for single user, private home usage. Unless you're a paraplegic, I'd say it's not that difficult to flip a switch. You'd put more effort into building this particular project than you'd put into flipping a switch twice a day for a few months, assuming your nearest hardware store is inside your living room.
what if your computer is tucked in a corner, and the power strip is behind it? then for some people you have to crawl under a counter, pull out your PC, flip theswitch, and push back your PC.
You could not make it so inaccessible. Mine is under my desk, but that doesn't stop me from getting on my knees twice a day.
True, the network boot feature isn't too useful for the average person. It is, however, very useful to someone running a Beowulf cluster. I use the feature to reboot my firewall remotely if for some reason a power outage lasts longer that the UPS, and it's built into every modern PC. No one even asked me first, they just put that in the standard. On my PC, it goes like this. I tell the PC to shut down, I wait about 45 seconds, and then I flip the toggle switch. I'm afraid to kill the power strip first because I have storage mounted over the network (NAT and a router) I could leave the router on 24/7 but I'll bet that would take more power than the PC's net boot usage. I'll check that next. Something like this would make my life easier. I like it. Oh and just a note, the test PC that I'm measuring happens to have 2 network cards in it. It use to be my old firewall. I'll see what it draws when I take one of those cards out too.
i've tried a few times to remotely start up and shut down my pc's from my laptop so that i do not have to go down stairs and turn it then on and off! however i have never managed it! my software was s**t!!! please can you tell me the software that works for you! i run on a windows enviroment and if you know how to shut down and boot up using ms-dos/cmd i would be happy to know
this feature is implemented in the hardware, not the OS, so a computer running (really not running, because it's off) anything should boot ok if it gets the magic "packet"

There are plenty of sites on the internet that can send that magic packet for you, try looking http://www.google.com/search?q=%22Wake+on+LAN%22

Here's one: http://www.dslreports.com/wakeup

also, check this wikipedia page: http://en.wikipedia.org/wiki/Wake-on-LAN , perhaps you need a cable to your network card?
THANKS, i was aware that it is hardware based and usally you can disable/enable in the bios i just needed the software/program to send the 'magic' packet anyway thanks for the links should solve my problem...
saadmanna4 years ago
i have worked on similar Project with Parallel port and serial port.
i am searching some thing like this but much more advance...so that i can control  at-least 8 switches with USB.
cboy2us5 years ago
This provides isolation?!?!?!?!, first lightning strike, you will pay for.
nforge cboy2us4 years ago

Isolated ground can mean a few different things depending on who you ask.  But typically the requirements for an isolated ground are that it's wired directly back to an electrical panel, not relying on conduit or other metal items to link it back to a panel.  But when it's in a residential application, this is as good as an isolated ground, it would be a straight run back to a panel, and as long as the box is grounded it's as safe as you'll get.  http://www.mikeholt.com/technical.php?id=grounding/unformatted/ig1&type=u&title=Isolated%20Ground%20Reference%20One

I love the retro Pentium 2. I tend to forget that we all owned one of those at one point. Great Instructional keep up the good work.
Arbitror5 years ago
So what's the Pentium II for?
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