New wiki article: Current activated switch

[The Natural Philosopher]

But it is invasive. It has to be connected in series.

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[John Rumm]

Not sure I follow?

There is no electrical connection - you loop an insulated wire through the hole in the middle of the CT.

[John Williamson]

No, the current transformer has no electrical connection with the load cicuit. It fits around the conductor, and senses the changing magnetic field generated by the alternating current flowing in the conductor. The conductor being sensed is not broken at all, although you do need to make sure that the sensor only goes round either the live or the neutral, not both.

[tony sayer]

You can of course put the current transformer in the neutral line its a balanced circuit as far as it goes if you don't what mains live potential anywhere near it.

We used this idea in a custom built generator controller where the mains had to go direct to the meter but the metering was done in the neutral return ....

[tony sayer]

In article , Arfa Daily scribeth thus

ISTR and I can't be that arsed to go look now but I think ours has some sort of hall effect or reed relay device near the outputs ..

Suppose another could be tacked on if that is the device in use...

[Dave Liquorice]

Don't worry about it. TNP is talking out of hole 2" behind his bollocks.

[fred]

In article , Fredxx writes

Jeez, everyone is a critic.

To all who have suggested they could do better, why not build and test your circuit and post it to the wiki as an alternative implementation. Until then, let's thank Arfa for his unselfish contribution.

Thanks Arfa.

[Dave Liquorice]

Bad assumption. What happens if the neutral goes open circuit after the device? Though with what we are discussing, a through hole CT, that isn't an issue but for something directly connected it is.

[fred]

In article , tony sayer writes

Dear dear Tony, a neutral is a phase conductor that just happens to be a zero potential at the moment (until disconnected) ;-)

[ARW]

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+2

[Bob Eager]

+1

[dennis]

can wire them in parallel.

[Arfa Daily]

I just knew he didn't understand ...

Arfa

[Arfa Daily]

All the ones that I have had over the years, have a small chamber immediately above each of the impeller output ports, and just below the flex-hose connection points. In that chamber is a weighted down 'almost float' with a magnet attached. Outside is a reed switch. When the shower valve is turned on, water flowing through the impeller housing under static pressure, 'sweeps' the float up to the top of the chamber, activating the reed switch outside, which starts the pump motor running via the speed control circuit. I did at one time contemplate paralleling up another pair of wires from one of the reed switches, but decided against this as it would involve partially stripping the pump, and soldering wires in there.

"Invasive", you might say ... d:-)

Arfa

Arfa

[John Rumm]

If you want to be a pedant, a neutral is a live conductor, but not a phase (or now "line") conductor... ;-)

[Andy Dingley]

You can even do it from _outside_ a multi-core cable (tiny Hall probe, it needs the conductors to have some space between them and calibration is a sod). Works fine for a simple "Is this thing on?" sensor though.

[fred]

I like to think of myself as a conceptual pedant, I draw the outline and let my team fill in the fine details later :-D

[John Rumm]

I think that would make a nice job title... conceptual pedant - pedantry in broad brush strokes at a national level ;-))

[NT]

It would be good to separate what applies to these autoswtiched sockets, and what applies to the electronic circuit presented. I may come along later and add a couple of other circuits using different approaches.

NT

[tony sayer]

Ever tried another sensor alongside the other one?. Would there be sufficient field to work both of them?..