Slightly OT:Electronic circuit

[Jethro_uk]

Can anyone suggest an electronic circuit which can take 2 400W loads, and switch instantaneously between them, so that to a connected monitor, the draw appears consistent (i.e. no spikes or troughs) ?

[Gib Bogle]

Try sci.electronics.design

[Andy Burns]

what sort of loads (AC or DC, inductive such as motors or resistive such as incandescent lamps or heaters)? are the two loads the same type of load?

[Jethro_uk]

Sorry, should have said for UK AC Mains. Let's say both loads are like a half bar fire - so plain resistive loads. I'm picturing a black box which plugs into the wall, and which has 2 sockets. When the load on one socket is removed, the box switches power to the other socket.

X-posted to sci.electronics.design as previous poster suggested.

[NT]

that's simple, just 2 triacs controlled by whatever is making the decision. Triacs would need to be switched at zero crossing to avoid any glitch.

The details of the switching vary depending on whether the load is resistive or inductive.

NT

[John Williamson]

And how fussy the monitor is about consumption spikes. Even with something like a cooker hob element or light bulb, there'll be a short term increase in consumption as it gets up to temperature, and if it's something like a capacitor start motor, the surge as it gets up to speed will be noticeable, to say the least.

Automatically switching from one outlet to another when one load is removed is not too hard to arrange, again depending on how fussy you are about cases where the load is unplugged at, say, peak voltage, and whether you're talking about millisecond current peaks and gaps or not.

[NT]

If the monitoring device isnt very fussy, a simple relay would do the whole job. If youre using say 1kW plug-in heaters, rewind the relay coil to operate on 4A, and the contacts will switch to load 2 when load 1 no longer draws current. To move back topowering load 1, unplug load 2 and press a button that momentarily connects power to load 1. The relay then latches. Note that the relay should switch the live, and its coil be in the neutral line, otherwise the pushbutton would short the coil.

NT

[Brian Gaff]

Depends on how inductive the loads are...

Brian