Introduction: Sustainable Automatic Power Supply & Sockets Shutoff

Picture of Sustainable Automatic Power Supply & Sockets Shutoff
Have you heard about standby power use?

This is when you turn your game console off from the remote control and think it does not consume any power from the grid ... this is wrong ... check this list below that shows the amount of standby power usage of some appliances:

        Appliance: (Range from Min to Max)(Average consumption of all sampled units)

  • DVD player:   0W to 10.5W;   1.5W
  • Subwoofer:   6W to 21W;   11W
  • Game console:    0W to 2W;   1W
  • Audio minisystem:   0.5W to 24W;   8W
  • LCD computer display:   0W to 4W;   1W
  • Notebook:   1W to 26W;   4.5W
  • Scanner / Printer Inkjet:   0W to 10W;  5 W
  • Set-top box Satellite:   7W to 33W;   16W
  • Power tool cordless:   0W to 4.5W;   2W
  • Microwave oven:   2W to 18W;   3W

Remember that these figures are true when the unit is off, but plugged into the grid i.e. you don't use your microwave oven or you pressed the off button on the TV remote control. If you work on the PC it could draw hundreds of watts from the grid. (Whole table here:

Lets say the average notebook draws 5W when it's not in use (it is turned off, but the battery charger remainss plugged) - i.e. the times when you are away from home or you sleep. Your audio system will consume 8W and the printer 5W standby power. This will roughly be during half or 2/3 of the day, so:

(5W+8W+5W) * 12 h/day * 365 days = 76 896 Watt-hours per year ... 

Now if you have 2 or 3 PCs the result multiplies by the corresponding factor.

And dependig on the local electricity price this equals to $7-10 per year per one PC set only. I am not trying to make a point about how you can save thousands here ... it is more about raising awareness around the standby power use.

A quote from Information and Electronic Technologies: Promises and Pitfall, 2004:

"Estimates of standby power consumption in the European Union (EU) range between 5 and 10 percent of total residential electricity consumption. Standby power is also consumed in commercial buildings (by office and building equipment and appliances, e.g., personal computers, copiers, phone systems, hot-water pumps, central computing devices) but is not yet well documented. A theoretical investigation (Menti 1999) suggested that standby consumption should account for less than 10 percent of total consumption in commercial buildings. However, actual measurements of 32 building appliances in Switzerland (Menti 1999) show that an average of 36 percent of total consumption is due to standby consumption at night (between 20:00 and 6:00) and during weekends."

Of course it is impossible to unplug everything that you don't use from the grid .... except from the frige apparently.

I am challenging you how you can design sustainable tools that fix these issues locally.

I designed a simple, very very simple circuit that detects when you turn your PC on or off and automatically turns the power supply on/off for you. Not only it does turn the power supply automatically on and off, but it can also do the same with the printer, speakers, your desk lamp ... or anything else that is powered from the socket  :)

Step 1: How?

Picture of How?

All  you have to do is plug a USB cable into your device - as simple as that.

If you lack free USB ports, you can use a USB hub, this is also fine.

The Sustainable Automatic Power Supply & Sockets system will be triggered by the +5V signal coming out of the USB cable when the PC is on.

Now it's only up to you whether you will plug your speakers, printer, desk lamp or maybe all of them into the Sustainable Automatic Power Supply & Sockets and start conserve power immediately.

I would like to hear if you like/dislike the design of my project. Do you think it adresses the sustainability theme or you wouldn't bother this much about the small things in life?

Step 2: Parts List

Picture of Parts List
To do the Sustainable Automatic Power Supply & Sockets you will need:
  • Extension plug
  • USB cable
  • Prototyping board
  • 6VDC relay x 2 - relay must be rated for at least 2A at 120V AC for the US or 2A at 230V AC for the EU (depends on the grid standard in your country)
  • Diode - N4007 is ok
  • LED and a resistor above 2 KOhms (optional)

Step 3: Unplug. Open.

Picture of Unplug. Open.



Now open the socket extender.

Step 4: Schematic

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I have drawn the schematic for you.

The USB cable supplies 5V that switch the relays on. The LED is just to unform you that there actually are 5V on the USB cable and you have it plugged into the PC. Note that the diode across the +5V and 0V must be there! This is to do with energy "released" from the relays when the power supply is turned off. This excess energy will do through the diode, not through your PC.

Check the datasheet for the relays that you want to use.

There should be two terminals that power the coil, two terminals that are shorted and they become open circuit when the relay is powered, and two terminals that are open circuit and short when power is applied. We are interested in the last ones - they will connect the high voltages to the sockets when the relays are powered up.

Step 5: Power Sypply to the Relays

Picture of Power Sypply to the Relays

Cut small pieces of the prototyping board and solder the relays to it.

Attach the power supply cables to the relays. Polarity is not important at the relay terminals.

Step 6: Detach Metal Plates

Picture of Detach Metal Plates

Cut the cables leading to the metal plates for the Live and Neutral power lines.

Detach the metal plates off the plastic part.

Step 7: Solder Metal Stripes to the Relays

Picture of Solder Metal Stripes to the Relays

Solder the little piece of cable that you left on the metal stripes to one of the relay terminals referring to yhe schematic.

At this point it is good to note that soldering is not the best solution. Bigger relays have bigger contact plates and cables are not soldered, but crimped and then connected!

I took an image from google to show the crimping to you.

Step 8: Solder Power Lines to Relays

Picture of Solder Power Lines to Relays

It is time to solder the power lines to the other terminal of the relays. Keep the colour the same.

Step 9: LED & Power Connection

Picture of LED & Power Connection

Solder the rest of the circuit.

Step 10: Fit All In. Attach USB Cable.

Picture of Fit All In. Attach USB Cable.

I drilled a hole on the side of the socket box to fit the USB cable through it. Then a cable tie is used to restrain the cable from being pulled out.

Solder the final cables adhering to the circuit diagram.

Step 11: Glue & Close

Picture of Glue & Close

Use glue to keep the parts tight.

Place the 5V circuitry far away from the high voltage. If needed, use some insulation material to isolate the low and high voltages.

Step 12: Finally!

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Done! It actally looks so discrete that I like it. I think it is beautifull and most importantly, it works!

Now enjoy your PC day and night and don't forget to unplug the power supply socket after you switch the computer off .... or wait ... no, there is no need for that ... why would you bother unplugging it now ... your PC charger will use exactly 0W from the grid when the PC is off! It is the same with your music woofer and the printer! How cool! It is automated to do so!

Please share your comments and ideas. Thanks!

P.S. don't ask me why I decided to put the lams stickers on the pictures ... I am not sure ... I just wanted some colour.


smilesudharshan (author)2017-06-09

Nice idea. Same can be done wirelessly using the below instructable

agis68 (author)2014-09-08

excellent! I guess this instructable's materials and supplies can be applied in 220V European plug....can you inform me if anything changes....(i guess the diode bridge must be for 220V) but what else....

Raphango (author)2013-10-25

Whoa! Really needed that! =D

PKM (author)2013-02-14

One final thing before you plug your TV, surround sound system, lamps, halogen heater, electric drill etc. into this: take the current rating of your relay (eg 1A), multiply it by your mains voltage (230 in Europe, 110 in USA) and that is the maximum safe wattage for the entire power strip. For a laptop charger and a small desk lamp it's probably fine but a desktop computer, LCD monitor and sound system together could well be over the maximum wattage.

This is easily solved with higher rated relays, but make sure the combined current draw of the two relays isn't higher than the 500mA you can draw from one USB port.

This is still a great idea and a very neat solution to the problem of phantom standby power usage.

hertzgamma (author)PKM2013-02-14

Yes, that is absolutely true! Thank you for the comment on my work :)

Tomdf (author)2013-02-08

That is very clever idea, nice work!

xKOBAYASHIMARUx (author)2013-01-27

Very nice man! Although the use of the kickback diode isn't necessarily required since the outlet is actually isolated from the 5V relay circuit, it is good habit. Only other thing is to maybe run spell check on your instructable and you're good to go! lol. Very easy and simple to do. :)

Jimmeh30 (author)xKOBAYASHIMARUx2013-02-04

If you don't fit the diode, you may find your usb port will fail, or worse your lap top. You should always install diodes across relays. Injecting several tens or even hundreds of volts worth of back EMF into equipment, is generally regarded as a bad idea.

Thanks! I will spell check it, and thanks for pointing this out!

orator (author)2013-01-27

A couple of things bother me about this project: 1) The 5 volt lines come much too close to the mains inside the plugs unit. They could provide a certain amount of 'noise' to the d c circuits and, if shorted, could supply your USB +5 with totally uncontrolled line voltage. NOT A GOOD THING! 2) The extender outlet, probably marked at 10 or 15 amps, is now good for a maximum of 2 amps (the value of the two relays). (Two 2 amp relays in parallel or series still are adequate for only 2 amps) The load on the extender needs to be calculated as if everything plugged into it was on at the same time. It would be better to use a larger current relay (15 amp) to control a single outlet for this extender to plug into. Also, IMHO, soldering is always better than crimping if done properly!

J-Ri (author)orator2013-02-04

You are right about two relays in series. However, in parallel they are theoretically good to double the rating of a single relay. However, due to inconsistencies in manufacturing and uneven wear during use, the resistance across the two will undoubtedly be slightly different. Because of this, they are not actually good to 2x the amps of one, but are could easily be 1.95x

orator (author)J-Ri2013-02-04

This would be true in a current carrying capacity. However, due to imperfection in transfer, would not be true in a switching application. One relay or the other would invariably contact or release before the other (although only very slightly) and would result in only one carrying the whole load at the worst possible time, that of surge or spike.

JayGeeBSE (author)2013-01-29

If it needs 2 relays for safety, there is a little snag - you have no idea if one relay has welded its contacts closed. Now you only have one relay and you don't know that the safety is compromised. I''ve even seen a sealed relay with a solder ball rolling around inside and shorting things. Yes, shorting things - meaning the mains and the 5V could get connected. It's already been pointed out the clearances between mains and 5V on the relay terminals are far too small for safety.

However, the criticism of the possibility of overloading the relay contacts is very simply overcome in the UK version - just put a suitable fuse in the mains plug, preferably adding a label stating the correct fuse value.

okokok1235 (author)2013-01-29

It looks like this will only work with a laptop that has a battery installed. Your comments indicate PC which would need a 5 volt source like a start button installed on the strip.

hertzgamma (author)okokok12352013-01-29

Well yes, not a desktop PC but a laptop PC. And the laptop must have at least some charge in the battery in order to power up the USB ports.

kjsrocks (author)2013-01-28

how would you use this for a surround sound syestem

florin2901 (author)2013-01-27

Hi there,
I'm using this "gadget" for more than 7 years..... but it is built a little different.
Because my computer case is always open, I use one free hdd power plug, from which I extract the +12 Vcc.
This 12 Vcc energize an relay which consume less than 2 mA. This one interrupt the main 220 Vca which it's used for my monitor, auxiliary 12 Vcc, audio line, printer and router.
All this time I use this "instalation" never fail, the USB socket in my computer it's always "ON" even the computer is off but connected to main 220 Vca.
I don't have any schematic right now but if there is someone interested, I will publish it.
Regards from Romania!!!

rondacosta (author)florin29012013-01-28

Hi Florin,
I am "almost" certain you are talking about a tower PC, therefore I for sure would be interested in looking at your wiring/schematic. It would be used for 110VAC in the USA.

Ghild.Zero (author)florin29012013-01-27

hertzgamma and you , Inspired me !!! thx alot guys ...
it open my mind about saving energy

hertzgamma (author)Ghild.Zero2013-01-27

That is why we are all here in Instructables - to inspire and get inspired!

ffievez (author)2013-01-28

Why putting two relays, you just need to switch off one terminal to cut the power

hertzgamma (author)ffievez2013-01-28

In some countries the power sockets and plugs have two ways of connecting and power/neutral lines depend on the way you plug them. It is more safe to have separate relays for each line.

pacheco.lourenco (author)2013-01-28

To be clear, the question below was: how do you turn it ON again you you don't have a battery to power USB and close the circuit?

Well with this circuit you can't do this.

We have commented on this topic below and one of the ideas was to have a mains button that would initially turn the sockets on. For this to happen, the circuit would look rather different and have more relays, maybe a separate plastic box to accommodate all the circuitry.

pacheco.lourenco (author)2013-01-28

OK, this works fine IF the USB is plugged in a battery powered device but, how about other modern appliances like TVs, STBs, Desktop PC,...?

jimvandamme (author)2013-01-27

Commercial models sense the current passing through one of the sockets, and control the other sockets based on that. You could use it for many other things, with no connection to the controller device except the power. However, that would take a current sensor and amplifier inside the strip. You'd need a small power supply to run it. Some engineering required.

hertzgamma (author)jimvandamme2013-01-28

That's the next version release!

The Lightning Stalker (author)2013-01-27

There is a downside which I have discovered. When the power is completely off, the device is now forced to rely completely on its battery to power the real time clock, CMOS (NVRAM on a Mac), and whatever else. This shortens the life of the battery significantly and can sacrifice some accuracy of the RTC.

Do you mean when you run on battery for example and do some stuff on the PC?

No, this is when it is "off". There is a small battery inside, usually CR2016, CR2025, or CR2032, but it could be almost anything. For instance on your notebook computer, I'm fairly sure it draws from the big lithium battery as long as it's in there and has charge. Otherwise there is another small battery inside.

On a regular desktop (tower) computer, there is only the tiny "CMOS" battery inside to keep the clock, etc going when there is no power. It can last over 10 years with power, but with no power only about 5. On some models it won't even last that long.

Now I get it. If you say so, this will be the same with every TV, DVD, game console etc. because they all have clocks and tiny batteries for their system clock.

anyheck (author)2013-01-27

This seems rather dangerous for your computer given that the high voltage is a mm from a direct connection to your USB port.

Why not use an opto-isolated relay board to afford protection. Here a two-channel one for $4

Still, you will need to supply 5v to the relay board from something else to enjoy its benefit to your computer. Like an always powered cell phone supply or something similar. You can also put in an override switch in case your computer is not there or your laptop battery is dead.

So you won't get to zero watts, but such is life.

-A-N-D-Y- (author)anyheck2013-01-27

Relays are an isolation device! :) as long as they are mains rated relays there is no advantage to complicating something so basic. There are commercial versions that sense the power draw on one socket (the computer connected one) and control the other sockets in a similar way

Moote (author)-A-N-D-Y-2013-01-27

It would fail CE accreditation full stop, as there is no protective isolation relays can'r be considered protective

-A-N-D-Y- (author)Moote2013-01-27

Not sure where you are putting your full stop but relays are exactly for isolating circuits, maybe not the ones used here but if you spec correctly it's a perfectly good solution, yes they should be double poll, yes they should be 13A rated (UK) but this is instructables.. if this was the most dangerous project on here then fair enough, I can point out many where it would be safer to go lick a light socket then build them :) Build this for yourself and know it's limitations and it's fine, don't plug your kettle and heater in tho :) It's a good instructable

hertzgamma (author)Moote2013-01-27

I suppose there is no 100% safe system and there is always a chance that something bad happens.

What I made is a very simple system and very primitive too. I will take all knowledge and make the next version as safe as possible.

jmjohnson85 (author)2013-01-27

I've been looking for something just like this because I have an Xbox 360 with some externally powered peripheral devices that I would like to turn on/off automatically when the 360 is turned on/off.

I'm fine with building it myself (thanks to your instructable) but I'd rather just buy something that accomplishes this. Have you seen a commercialized version of this or something similar?

Thank you and keep up the great work.

spudit2003 (author)jmjohnson852013-01-27

I've been using a device that achieves the same thing for a few years, i got given it by an energy company. it has 3 sockets, 1 master and 2 peripherals, so the master is always kept on (so you can turn the PC back on again) and it detects wattage. You can buy them on amazon:
they also do ones for TV systems which have a remote sensor, and are usually strips rather than blocks, but it can be awkward using the standby button because it can be slow to respond (so by the time you realise your stuff is powered you've turned it off!)

Homee2010 (author)jmjohnson852013-01-27

I wish I had seen this before I purchased two "green" power strips!!!
To JMJ: there are numerous manufacturers that sell these power strips. Of course, making your own is more fun!

florin2901 (author)2013-01-27

for "hertzgamma "
You can use COM port if you have one, but there you need some circuit which will convert signals from it to Vcc.... I will study this situation....

hertzgamma (author)florin29012013-01-27

To tell you honestly, I have a COM port which is quite rare on a laptop, but have never seen what kind of signals come out from there.

Chybis (author)2013-01-27

Small question here - maybe I overlooked some detail, but it seems both L and N wires are switched by relays. Would not be better to switch off just L wire (live wire)? It is done that way usually, you save one relay, and it is more secure. In case L wire relay fails with contacts closed (switched on) and the circuit gets disconnected by switching off N relay only, appliance appears switched off, but 110VAC may appear on some parts of the appliance connected to the outlet. Especially if it uses 2 wires only (as with 2-wire plugs).

hertzgamma (author)Chybis2013-01-27

Most european contries (all except the UK) use a power plug that can be plugged in two ways because they are symmetrical and by rotating the cable at 180 degrees it also plugs normally.

It is more safe to put switches to both L and N wires.

xKOBAYASHIMARUx (author)Chybis2013-01-27

N and L are just references. Even though it is common practice to only switch the live wire and in most all cases it would be fine, the neutral can still be used for power, even in 2 wire plugs depending on how the outlet is wired. To be safe, relay them both.

-A-N-D-Y- (author)Chybis2013-01-27

Always better to switch both.. you don't know what idiot messed with the wiring further up stream :) but double poll relay SHOULD be used, using two is bad practice for the reasons you state :)

onemoroni1 (author)2013-01-27

Nice instructable. I have been concerned with "electricity vampires" for a while and have bought the old computer power surge protected monitor bases with the switches in front to use with my desk top and other applications where I manually kill the master switch for all devices.

MichaelAtOz (author)2013-01-27

I suppose you chose the relays based on size to fit the case?
They are totally wrong, as someone pointed out with the soldering the live wire is way too close to the black wire, bad soldering, flexing of the cable etc could short the connection and you have grid voltage at the tip of your USB connector, not good for your PC but really bad for you!
Anyone attempting this must as a minimum test all connections with a multimeter to ensure there is no crossover.
Also as someone else pointed out 2A is not good enough if someone happens to see a spare socket and plugs in a larger appliance you risk fire! The relays must be rated at least the same as the whole power strip (usually 10A), ideally higher (16A).

hertzgamma (author)MichaelAtOz2013-01-27

I see your point here. I have not written this in the instructable, but I made lots of measuring to ensure that things do not fry when connected. And absoutely for sure, the relays must be rated for higher amps, but all I wanted in my project is the laptop and speakers supply chain.

As I have mentioned - I understand that soldering is bad for high voltge connections and short and unflexible cables - these must be done with the crimping shoes and crimpers shown on step 7.


Kdemon (author)2013-01-27

I like your power strip! I bought a commercial one called TrickeStar for my home entertainment system, I like the idea of using the load of the master device to controll the slave to that device. My TV is the master and controls my game consoles, surround sound, appleTV, ect... Maybe I can work on your power strip design and manipulat it for electric load, for my computer system.

hertzgamma (author)Kdemon2013-01-27

Cool thing to have around the house, a master device that knows what happens and when to turn the power on or off.

About This Instructable




Bio: I am a University of Edinburgh electronics engineering student.
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