Extension block switches neutral not live


I have a master slave extension block that automatically switches on/off

6 slave sockets when whatever is plugged into a master socket is switched on/off, in this case my PC. It is labelled TCM, I bought it almost a year ago.

The other day it stopped working and me being me I took it apart to see what was wrong (I was trained as an electronics engineer).

I found the problem (a blown thermal fuse) but I was gob smacked to discover that it switches the neutral and not the live, i.e. the slave sockets are turned off by isolating the neutral and the live is still live. *

Is that legal? (I'm in the UK).

  • That explained an odd behaviour I saw a few months ago when a PC speaker system I bought remained powered when plugged into the slave sockets even when they were off, it guess it earthed some part of it's PSU for some reason.

Regards Chris

Reply to
Chris Glen-Smith
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I wouldn't think it is legal in any part of the world. It certainly isn't in North America. The potential for shock and death is very high, especially if a child or infirm adult touched something hot while grounded. Throw it away and check any replacement you buy.

Reply to

Only if it is a Low Voltage Control Master/Slave System

Where the AC [household] Outlet is shut on & off by the Masters Command to Trigger the Slaves.

No Killer AC actually runs through it, Only Conventional Receptacle Dangers Apply, check your Polarities.

Reply to
Roy Q.T.

Is it an X-10 system ?

That's very cool, how much did it cost you?

Reply to
Roy Q.T.

If it keeps giving you trouble, do llike Rusty says, throw it away immediatley ! }:-o teeheehee

Toss It All in Rustys' Garbage Can}-)

or givem here, i'll dispose ovem for ya };)

Reply to
Roy Q.T.

Get a power strip with a switch on,like mine.When you switch off your computer, switch off that too, so that everything connected on it will be off.They are cheap, here you can get one for less than 5 euro.

-- Tzortzakakis Dimitri?s major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr ? "Chris Glen-Smith" ?????? ??? ?????? news:eGGCd.558$u snipped-for-privacy@newsfe2-win.ntli.net...

Reply to
Dimitrios Tzortzakakis

Is this product CE marked?

I think that you will find that the device is not legal and you should speak to the Trading Standards Office in your area.

Reply to
Paul E. Bennett

Hi again

I don't know what an "X-10 system" is, sounds flash, this is just bit of flex with a mains plug one end and a box of sockets etc the other, it cost 12 UK pounds of so I think, from a gadget shot in the mall.

It worked well, it was convenient being able to select shutdown and walk away know everything would switch off after the PC shutdown. I can easily repair it but I'm not sure I want to use it now.

Killer AC definately runs through it! Except for the sockets it's all on a PCB. The feed to the Master 230VAC live does a couple of turns round a toroid core to sense the load which drives some electronics which drives a relay. The relay contacts are in series with the slave neutral, the slave live is wired directly to incoming live via a PCD mounted thermal fuse (temperature sensing solid state thing I think, not a "fuse" fuse.

The master socket is always on (i.e. it's unswitched) while it is plugged into the wall socket, perhaps that makes it OK to leave the slave socket lives live even when it switches them off.

Mostly I'm just amazed it was certified (or whatever the approval is) for sale.

Cheers Chris

Reply to
Chris Glen-Smith

Hi Paul

Yes it has a CE mark> Chris Glen-Smith wrote:

Reply to
Chris Glen-Smith

It is likely that your wireless device has an input circuit with a dc voltage across the inputs when the input is open (that is how the open contacts are sensed). One side is likely common with one terminal of the battery.

You should try putting a power FET device across the input (source and drain) and using a capacitor from source to gate to hold the FET on for a period after your relay opens. A resistor across the capacitor sets the discharge period. I would start with 470 MF and

1meg resistor for 4-5 minutes delay (depends on gate voltage on turn-off, device specific).

If the battery negative is common to one of the input terminals, use a N-channel FET (I did something similar with an IRF520, way over kill on current, but you are not likely to damage it). If the wireless device voltage is only 3 volts, you will need a FET designed for logic level gate voltages.

Connect as follows: Source of FET to - input terminal Drain of FET to the other input terminal Capacitor negative (use 16V cap) to Source Capacitor positive to Gate 1 meg resistor across capacitor 100K resistor to battery +, other side of 100K to one of your relay contacts Other relay contact to Gate.

Use a grounded soldering iron as the FET gate can be damaged by static electricity.

If the battery positive is common to one of the input terminals, use a P-channel FET and reverse all polarities listed above.

When the relay contacts are closed, the 100K resistor uses the battery to charge the capacitor. Voltage on the capacitor keeps the FET ON.

When the relay contacts open (on power fail) the capacitor holds a charge while the 1 meg resistor discharges the capacitor. At some low voltage on the Gate, the wireless sensor will detect an open circuit and send the alarm. Experiment with resistance and capacitance to get an acceptable time delay.

If you shop the parts, likely cost per circuit is USD $2.00-4 .00. Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz

Reply to
Bill Kaszeta / Photovoltaic Resources

Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz

Reply to
Bill Kaszeta / Photovoltaic Resources

X 10 is registered mark and has a totally wireless control for household ac receptacles.

Your's is just a Hardwired Extension with receptacles attached to it, Not much remotes controll as we assumed, furher more, you have 220vac and you will always have a Live Wire present on your Receptacles Line In., the system you have employed is obviously for use on a 110 system where there is 1Hot and 1Neutral] { In your 220vac household system there's 1Hot and 1Return also Hot for control purposes there is a little more considertion that one wire isolation for the elctronics to perform.

Tidy it up and send to one of your US Buddies we would have no problem with it.


Reply to
Roy Q.T.

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