A few years ago, I recall seeing multiway socket blocks like those commonly available today, except they had one master socket, which when a load was drawn, switched on all the other socket outlets. The idea is the master socket was for a PC base unit, and all the other PC peripherals plugged into the auto-switching outlets.
Now that I want one of these, I can't find them anymore. Does anyone know if they still exist? Did I dream the whole thing?
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socket, and a surface mount back box... (If you are planning on using it for a PC)
Simply run some two core wire out of your PC (Mounting a suitable socket on the back of the pc is good if you may wish to disconnect it easily)
Connect these to the black(-) and the yellow(+) wires that goes to one of the large four pin plugs in the PC (For the hard disk, CDROM, etc.) then connect the other end to the relay coil.
Now, get a length of 13A mains cable (If you have a spare PC IEC Cable, just chop off the IEC end, leaving you with a moulded plug and a length of wire) connect a normal three pinned plug one end, and connect the Neutral and earth to the socket.
Connect the live to the common of the relay, and run another wire (the same thickness as the live you just connected) from the N/O contact to the L of the socket
If you had a double pole relay, you can switch both the live and the neutral
Make sure all the connections are nice and secure, and make sure they are well insulated, we don't want to end up shoving 240v into the PC's 12v circuit!)
Make sure you use some kind of strain relief, so the cables cant get ripped out too easily (Cable ties are usually good for this)
Screw it all together, and now when the PC is turned on, the relay activated, thus turning on anything connected to the new socket...assuming you plug the other end into the mains!!
If you can get a suitably rated 5v relay, you could get power from the PS/2 or USB port - I just used a 12v relay, as I had one knocking around!
Sparks...
I'm so glad you didn't say 'easier'
..
Well no, but it's a LOT cheaper than £55.57!
It isn't as hard as it may look, I just tried to explain it in as much detail as I could ;-)
Interesting idea, but it doesn't include filtering etc. and probably invaidates the PC warranty (if one cares).
.andy
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I use exactly that on mine, but then it has a switched IEC outlet originally designed for the monitor before all those external peripherals became the norm.
Alternately, fit a FCU in a convenient place feeding a dedicated 13 amp socket for the PC and accessories.
I've got a circuit for such a device if you'd like it. I've not tried it, though.
Or you can buy a module that does it for you from CPC. Costs about =A320.
Well it's cheaper right up until the moment that the back EMF from the relay coil fries your PSU or the relay contacts weld and some other unexplained f*ck up results in 240V being presented to the 12V line in your PC simultaneously frying the MoBo and the drives.
Then you just end up feeling like a bit of a prat.
Awww, come on, is this uk.d-i-y or not???
Yes, it's just there are better ways of doing it, as Dave Plowman has already suggested.
You can get relays with diodes for this, you know!
Christian.
All one essentially needs is a relay and some wire. Cut the wire off the relay coil and rewind using thick wire. Now put the relay coil in series with the PC's mains feed, and use the relay contacts to switch the live that goes to the peripherals.
You could enclose it inside one of those 6 way socket strips, cutting one of the strips to give the 2 separate circuits. Then to use it you plug PC into the first socket, and that controls power to the others.
Regards, NT
You'd be mad not to have a diode across the coil anyway...
That would be a pretty unlikely event - a good relay is a perfectly acceptable way of isolating mains, and something pretty bad would have to happen for mains to end up across the coil.
That's no more likley then the PSU failing, and doing the same really
In fact, it is probably more likely the PSU failing, and presenting 240v to the low voltage side than the relay failing in the way you suggest.
A relay has true isolation in between the two circuits, an "Air Gap" - The PSU will be a switch mode type, where the mains is simply chopped up providing no "air gap" in between.
Sparks...
Most ATX power supplies do not have a switched outlet anymore, some have an IEC outlet, but it isn't normally switched, bring back AT PSU's!
Sparks...
In message , Sparks writes
I can assure you that every PC power supply has "true" isolation between the mains & outputs. The transformer (high-frequency ferrite core job) will have reinforced insulation or equivalent, type tested to 3000Vac. All other components crossing the "isolation barrier", generally just opto-couplers, be similarly rated for reinforced insulation.
Incidentally I have done exactly as suggested earlier in the thread, a
12V relay powered from the PC PSU switches on the monitor, printer etc. Pre ATX I just used a multi-way strip from the switched IEC outlet.A word of caution to those doing this.
***NOT ALL RELAYS HAVE SUFFICENT COIL TO CONTACT SEPERATION DISTANCES.***(Even where the contacts are 250Vac rated.)
You're typically looking for >=8mm ("creepage & clearance") between any live mains part and any coil wiring.
Best option is probably one on the large plug-in relays, with the appropriate screw terminal base (Finder 41 series in Farnell, or if you want PCB mount, Omron G2R series)
I had already thought about switching from the PC power supply. I might revisit that. I would probably use a opto-isolated triac driven by power from the unused games port or piggy-backed off the keyboard port (which is fine for the old PC involved here, but some newer PC's provide continuous standby power to the keyboard). The triac would switch a mains relay.
The circuit I've got somewhere IIRC measures voltage drop across large diodes (I think parallel connected in reverse phase so the voltage drop is small) then an amp feeding a triac. Never got round to testing it, though. Was in some mag or other.
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