Does anyone know of a zwave module that is a simple switch but is powered by 3-5v?
Ive been looking at a zwave based home automation system but all the switch modules are for 240v AC. I just want to be able at add the capability to switch a PC on and off using a zwave controller. any thoughts welcome 
You can turn one on using WoL, but I don’t know how you’d turn it off…
I’m not familiar with ZWave stuff at all.
I was looking at http://www.fibaro.com/ its a really nice solution. They have a relay module but it requires 24 - 60V DC or 110 - 240 vAC and its expensive gear.
Im not sure how i could get 24 v out of a PC PSU to power the relay though.
@ Hugh, whats the use case in detail? Why do you think the low voltage is a desired outcome/requirement?
The main reson is this. I have a windows PC running vista that has a dual tuner etc running media centre that acts as a DVR etc in the lounge. Its currently on 24x7 as i use ot to record tv programmes etc. what i wanted to do (to save on the old power bill) was to turn it off cleanly at about 12.30 am and and turn it back on at about 3 pm when the wife and daughter come home.
The only way i can see to do this niceley is to have a relay that connected to the rear of the power switch inside the PC. This would shut the machine down properly and avoid the problems of just cutting the power.
Im just at the start of planning out a home automation system so its all fairly new to me. The Zwave stuff (particularly the fibaro system) looks very nice but its pretty costly.
Im sure that there are other alternatives out there but i havent found them yet
Virgin Tivo 
Option 1: you can put windows in sleep (by a task in Task Scheduler) and set an other task to wake it at a certain time.
Option 2: some BIOS’s (like DELL) have a setting to wake a system at a certain time. Then set a task in Windows to shutdown at a certain time.
Option 3: see if you can get EWF filter (Enhanced Write Filter) installed on Windows Vista. With this filter all writes are redirected to a RAM overlay and you can safely pull the plug at anytime. You can even screw up the whole system, just reset and everything will come back as normal
(Funny, I installed the EWF filter on my XP pro box in the garage yesterday)
Option 4: install solar panels with inverter and leave the PC running 24/7
(BTW: I choose option 4 togetter with SSD instead of HDD and fanless embedded PC that only consumes 60Watt)
@ WouterH - Yeah you can put it to sleep and wake it up with Task Scheduler
@ WouterH and @ Justin
Thanks guys this is V helpful. I had totally forgotten about task scheduler! Doh
Ive also just found http://www.micasaverde.com/vera-3.php which can use Zwave, Insteon and X10 devices! Cool and its cheaper than the fibaro cooooool!
For 300$ (250EUR) you can let your PC running for YEARS.
I’ve once calculated it and having a PC running 24/7 for 365 days costs about 50EUR. So if you can safe 25% of this (remember, your additional equipment will consume extra power), this would make a safe of 12,5 EUR per year. So to get back the investement of 250 EUR, it would take you 20 years 
Actually, Vista and Win7 have good capability to sleep and awake as needed for instance if a 3am show you really wanted to record came on. If you want to always start the machine at 3pm, ie pressing a button was excessive/undesireable, you could set up a scheduled task to wake as the others mentioned. You’d need to tweak return to sleep time in case it decided to spool back to sleep after the fact but before they arrived.
Thanks guys I’m going to look at the task sched and see if I can get this going.
If you’re using Vista or later, and you’re not using S3 sleep instead of turning your machine on and off, you’re missing out. Turns off essentially instantly, turns on just as fast, and everything is right back where it was before you shut it down.
If your particular S3 sleep setup isn’t working, it’s worth figuring out what’s wrong and fixing it.
I’ve had varied success with this. It seems to depend a lot on having particular hardware. I used it for a while but it got to the point where I was having to reboot every time I came out of sleep mode because my keyboard & mouse would no longer respond properly. I’ll give it another try soon after I rebuild with Win8. It was great for the short while that it worked.
If you’re running XP, your experience may not be ideal. It’s been my experience that XP wasn’t as good at this as 7 is. I never had a single problem with 7, and haven’t yet with 8. Make sure your device drivers are up-to-date, especially chipset drivers, and you may want to update your BIOS if there have been changes that could improve things. Don’t do that on a whim, though.
I’m using Win7. Considering that it did work for a while, I think something just got messed up on my machine and the clean install of Win8 will probably fix it.
Ah, yes. Good luck to you, it’s great when it works!