Smart Master/Slave Power Strip for Your PC [mod] (self Shutdown But Zero Standby)




Off should be off. And usability should be good.
To make it short: We did not find the right product out there, so we ended up modding one.

We bought some "Energy Saver" power strips from Zweibrueder. The devices are
very solid and not very expensive. They feature an external switch and no further intelligence.
You can place the switch in a good spot and leave the cabling under your desk.

The major drawback when using those power strips with manual on/off switches
on PCs, is that you'll have to wait for your PC to shutdown completely before pushing the off
switch. (which can take some time when running Windows ( ... installing Update 12/24 .... do not turn off ....)).
You shouldn't press the on/off-Button before complete Shutdown for obvious reasons.

To make it short: We did not like it. Nobody wanted to wait for shutdown.

The perfect power strip should:
- turn on the PC when turned on
- turn off itself completely (and all devices attached to it) after PC has shutdown
- waste NO energy while off

We came up with the idea to mod the power strip to a USB-powered power strip.
USB Ports deliver 5V as long as the PC is running. Every PC has USB-Ports and 5V are nice.

The scenario:
1. Push Switch on power strip
2. PCs turns on itself (BIOS Setting: restore state after power loss)
3. USB-Ports on PC supply 5V immediately
4. USB/5V powers optical relay and sustains power for PC
5. Switch on power strip can be released
6. power remains as long as the PC delivers 5V
7. After PC shutdown: 5V are missing, relay is not powered any more = everything is off

The roadmap for this mod:
- mod on/off switch to push-button
- install optical relay to override push-button during on-state
- install USB cable to power optical relay during on-state
- fit everything into switch housing

This is just how WE did it. This should only show you what is possible and leads
to a good solution.
Only try if you are aware of the high voltage running through this.
We are not responsible for anything.

elha2 - Harald Elsperger
xpecto AG

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Step 1: Parts and Details

You need:
- "Energy Saver" from Zweibrueder
- USB Cable with normal USB-Plug on one side
- some heat shrink hose
- optical relay / SSR (we used Sharp S202SE2) Datasheet
- fitting Resistor for 5V, here: 330 Ohms (see Comment below)
- Tools for cuting, welding ...
- Screwdriver (we needed to make a small cut to fit the screws, so we used a old one)

Working Point of the Solid state relay:
The typical working point is 20mA and 1.2V. (min. 8mA, max. 50 mA)
This way you'll need:
(5V - 1.2V) / 0.02 A = 190 Ohms. We choosed a 330 Ohms Resistor as it
was laying around and just draws 12 mA from the USB.
There is a note in my datasheet that the SSRs degrade over time.
This is the reason for going not to close to 8mA.

Designed for PCs
We selected parts for "normal" PC loads. You shouldn't run big loads like Motors or
Machines from the Power strip.

The Design even works well with some Satreceivers and Flat-TVs who have a USB-Port.

Step 2: Open External Switch, Change to Push-button, Begin Wiring

Use Screwdriver to open Case. Tear everything out.

Use Pliers to remove Spring on the Bottom of the Switch.
This way the Switch becomes a push-button.

Free contacts on Switch with knive.

Remove Wires from Contacts on the right side.

Step 3: Free Up Some Space, Put Everything Back In

You'll need to mod the case a bit. The Relay has to fit in and we want the
Status LED/Lamp to fit in as well. You should try yourself.

Put everything back into place.

Solder the two wires and one contact of the Lamp together and heat shrink it.

Step 4: Solder Relay

This is the tricky part.
You'll have to solder the Relay in a way that it bridges the remaining two contacts.
We put some solder on the contacts prior to mounting.
You'll have to bend and adjust the Pins of the relay in a very special way to fit in.
Please take care otherwise the pins will break.
See photos.

Solder the relay to the contacts.
Take care, they need to survive the full power plugged into the power strip.

Step 5: Add USB Cable

The Relay is in Place. So we need power for the Relay.

Cut the USB-Cable, bring out the black (GND) and the red (+5V) Wire.

Solder the 330 Ohm Resistor to the Plus/+ Pin of the relay.

Solder the black (USB) wire to the Minus/- Pin.

Solder the red (USB) Wire to the other end of the Resistor. Apply Heat shring tubes.

Step 6: Cut Hole, Put Together, Done!

You should cut a hole for the USB-Cable.

Assemble everything. Put the screws back in place.

Congratulations! You're done.

We found the newer ASUS-Boards do not power of the USB-Ports after shutdown.
We simply faked an USB-Port (remember you only need 5v) with an old USB-Breakout-Cable and
an attached Molex-Powerconnector (like Harddisks).
Simply attach a Harddisk-Cable to the 5V-Line of the
USB Port. I'm sure there is a instruction somewhere how to do it.
(just connect red and black, cut the rest) As you'll connect only
5v on the USB-Port, you're able to connect every USB-Device there without destroying it.
See Photo



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    32 Discussions


    8 years ago on Introduction

    i cant quite see how this works
    but if you go buy the other designs for similar power strips then your pc never gets turned off. you plug your pc into a normal outlet or strip and then plug your speakers,external hard drives, monitors, printers into this and they get turned off when you turn off your pc


    8 years ago on Introduction

    My computer powers its USB ports, even when off, well, at least the hub for the front panel/internal header is powered as long as the little switch on the back of my PSU is switched on, allowing me to use my, this likely wouldn't work for me...


    9 years ago on Introduction

     i like this.  i've been looking for something similar except mine involves a laptop and i would like the power to the laptop to turn on whenever the power drops below a certain percent and completely shut off power when the laptop has above that percentage charge.  Really good idea.

    1 reply

    Reply 9 years ago on Introduction

    that is an interesting idea but it would be fairly hard on the batter, laptop batteries can only be charged and discharged a certain number of times before it will no longer hold as much of a charge and eventually no longer hold a charge. You would run a risk of "wearing out" your battery faster.


    9 years ago on Introduction

    I have Macs, and they don't shut down the USB while in sleep, because they have to be waken up with keyboard or mouse. I figured out that the LED in mouse is not lit, when the computer is in sleep. So I took an old optical mouse, desolded the LED, added a small capacitor ~ 10 uF instead and used a solid-state-relay to switch everything else (2 monitors, scanner, loudspeakers, external Time Machine FW-drive, lamp for keyboard etc.) on/off. Works beautifully since couple of years. I've made around 5 of these for my relatives and friends. I use this also for my (PC-)laptop at work, even switching the powersupply. So it won't be on at nights and week-ends. This didn't work with my wife's Powerbook, because she doesn't use it long enough to load back the energy used in sleep.


    10 years ago on Introduction

    That's quite a neat idea. What happens if you need to reboot the computer though? I believe on my computer, and I assume others, the USB power briefly turns off during a reboot. Would that cause the relay to switch off the system power?

    2 replies

    Reply 10 years ago on Introduction

    PCs (at least the ones we have here, mainly ASUS Motherboards) do not interrupt USB power during restart.


    10 years ago on Introduction

    I need a similar thing but don't want USB control. I have a TV and want to turn on/off my audio reciver and DVD when the TV is on/off. There is no USB outlet on the TV. Can someone figure out how to make a circuit that when it detects current (from the TV being on) to turn on a power strip and turn it off when the TV is off (obviously I won't plug the TV into that strip!). Thanks!

    1 reply

    Reply 10 years ago on Introduction

    these things are around since years. I think they are called master-slave power strips. you have one master outlet, and some slave outlets. the slave outlets are only powered if the master outlet uses an certain amount of power.


    10 years ago on Introduction

    Nice, but it will be much better to add a simple timer (you can use 555 ) for about a minute when pushing a on/off button. So it's not necessary to keep pushing the button until the 5V comes into USB and also it helps when turning off and on the computer very fast, so it's not necessary to push the button again! Good idea anyway! :) Thank you

    2 replies

    Yes, But it's no necessary to keep the timer on for all time the push button will close timer circuit and timer keeps it's state! See, no power consumption during off state!

    mr monoply33

    10 years ago on Introduction

    I just skimmed this, because I nee to leave soon, and I will never come back to it if I dont look now, even if I bookmark it, I will still ignore it, so correct me if I'm wrong, but this essentially unplugs the PC and other devices, if so, this will give quite a beating to delicate parts of the computer, more so the power units serge protector, and scanner bulbs, and printers that are more computerized, like the all-in-ones, that read camera cards, because when you plug an electronic in, it does get a little bit of a serge and or short (anyone that has ever plugged something in slowly like a fan into a higher grade outlet knows about the spark) also, this could do quite a number to a bios battery, they will hold a charge for years on end of non use, but being used, then cut off from the normal charging point....nothing in the first few months, but after that, your system may have problems. and sorry If I did miss read this, and its not a complete power off, I noticed the line "set bios settings to 'when power loss, restore system state'" or something like that, it will also do a number to hard ware, there's a reason your hard drive preps its self before shutdown.


    10 years ago on Introduction

    im wondering if you can use this for multiple computers with out it breaking the resistor


    10 years ago on Introduction

    I have seen PC's that keep power on the USB ports when powered off, for using a power button the keyboard or a wake on keyboard/mouse events. If you happen to encounter this, look in the bios for any "wake on..." options and disable them , this should allow the USB ports to stop providing power then the PC is otherwise off. Even if you aren't using this i'ble, if you don't use a keyboard mounted power switch it's worth making sure the wake on settings are all disabled. Not only does it save some power, but it will prevent a cat or child from "accidentally" turning your PC.


    10 years ago on Introduction

    Nice work. I made a very similar thing a couple of years ago and it is very effective. Well worth doing.


    10 years ago on Introduction

    A short turn-off delay can be added easily for PCs that power down the USB port on reboot. Just add a series diode with a small 10V (or greater) electrolytic capacitor behind it. I can't easily calculate the cap value without knowing the exact load of the relay, but it would be easy to experimentally determine a good value as the turn-off time will be pretty close to proportional to the capacitor value. Put a resistor in parallel to the cap on the order of 10 times the relay limiting resistor to make sure the cap discharges completely after the relay turns off. That will eliminate any possible chatter at the turn-off point.


    10 years ago on Introduction

    This is very well done! I have a few questions, for which it might be nice to add the answers into the body of the I'ble. The relay is, of course, drawing a little power from the USB circuit as long as the PC is on. Do you happen to know the current draw by the relay (which x 5V will give you wattage)? Why did you choose an optical relay? Was it just to have a small enough form-factor to fit? Or does it draw less current than a mechanical relay?