Instructables

Smart Master/Slave Power Strip for your PC [mod] (self shutdown but zero standby)

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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

DISCLAIMER:
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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joshnosh3 years ago
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
Hycro3 years ago
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 computer...so, this likely wouldn't work for me...
cdubnbird4 years ago
 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.
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.
maukia4 years ago
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.
seanm29a4 years ago
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?
dschie seanm29a4 years ago
you could use an elko to bridge that power gap
elha2 (author)  seanm29a4 years ago
PCs (at least the ones we have here, mainly ASUS Motherboards) do not interrupt USB power during restart.
2schnauzers4 years ago
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!
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.
mamad8764 years ago
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
True but that would defeat the purpose of no power when off.
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!
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.
mman15064 years ago
im wondering if you can use this for multiple computers with out it breaking the resistor
chrwei4 years ago
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.
dbrf4 years ago
Nice work. I made a very similar thing a couple of years ago and it is very effective. Well worth doing.
strehlow4 years ago
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.
sweet plus nice soldering tip
kelseymh4 years ago
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?
When mechanical relays change state (turn on or off) they produce a voltage spike. This voltage spike can be destructive to the computer itself. Using an optical relay, all the computer is really powering is just an LED, one big enough to change the state of the photo transistor. This does not produce a voltage spike, and is safe to use without a protective diode.
Or use a solid state relay, optoisolator comes packaged in the triac driver circuit such as the MOC302. When paired with a larger triac it can safely switch more current than your power strip can handle. Just be sure when designing the SSR you know what you are switching with it, for large inductive loads there are special circuit designs or certain triacs which are designed to handle these loads. There are many benefits to SSR's including lifespan, capability to be used in explosive environments (no contact arc), soft turn on for devices, etc. I would recommend building from scratch sourcing parts from Digikey as opposed to using the prebuilt SSR's you can buy if you have the knowledge to build one. It is always best to know what the limitations of your circuit are and the best way to do that is to know what parts you put into it.
elha2 (author)  Swishercutter4 years ago
Very good comment. The SSR's are cheap and fitted our specs. It was designed for small loads like PCs. Your suggested solution sounds very good. This is the way to go when looking into mass-production of those things.
Sorry, MOC302 should read MOC3021
elha2 (author)  kelseymh4 years ago
Thanks!
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.

A mechanical Relay:
We did not find the perfect relay. The spike when turning on the coil must be compensated. The SSR seems to be a better solution.
RetroTechno4 years ago
Very novel idea! I am sure someone will build upon this. I would suggest putting in some sort of protection on the USB wires so that the mains will not get back into the PC in case of some sort of catastrophic failure. Perhaps a zener diode and a fast-blow fuse.
elha2 (author)  RetroTechno4 years ago
Thanks!
I think the SSR was a good idea. I added a link to the datasheet.
The SSR is optical isolated (3kV), that should do it.

The protection needed is an Optoisolator. There are many forms of this and they are cheap.
jolshefsky4 years ago
I've got the same thing on my computer ... sort-of. Since it's a laptop, I have it start-up from the battery but when the power comes on, that includes the power/charging brick. I also have it with relays to switch out the USB hubs and devices until the computer has been on for a minute or so; plus it gives time for those devices to settle after being powered-on through the hubs. I like the push-and-hold switch concept as well.
l8nite4 years ago
someone should patent this then market it for those of us with less electronic skills, I understand the concept and like it, the rest may as well have been written in martian = )
I have done something similar here,http://www.instructables.com/id/A_USB_Power_Controled_Plug_Strip_With_Isolation/ It was s similar idea, not quite as slick of a way of doing things, and has its drawbacks, But there are some really good bits of information that people have left in the comments section that are worth a quick read for someone building something like this. And some of the quirks of SSRs are revealed.
Nice job,
Toymotorhead
I was actually in the process of ordering parts to build some solid state relays from scratch. I was going to build basically this same thing...I will make an instructable once I actually get this done. Also, if you use a solid state relay there will be a "soft on" as opposed to a magnetic relay, plus the chip to drive the triac in the solid state relay is an optoisolator which operates on 1.8-18V DC turn on voltage (specs on the one I am using) so you don't have to worry about the inductive kick from the relay coil (even though a simple diode snubber solves the issue, 1N4148 for the diode I belive.) Good job though.