using a 12v switch to operate a 240v appliance

[xelaris]

Ok, here we are entering the electronic area (more than simply electrics), but this simple project might have huge potentials for anyone....

The basic problem is this:
I have a brand new enclosed shower cubicle - it has all the basic functions and more, including a fan....the latter is operated via a switch sited conveniently inside the shower (obviously 12v). Now, I expect this fan to give a poor performance - (just by looking at it)....I'm thinking of replacing it with a better one.
There are some promising SELV fans on the market....still, I'm tempted to go for the more powerful in line type - simply because it would allow me to connect an extra extracting vent in the bathroom (no just in the shower cubicle)...still, the main reason for requiring a more powerful fan is that there's going to be a few bends and probably 4m ducting (flat channels).

It would be ideal if the 12v trigger inside the shower could switch the 240v fan on and off - or maybe in conjunction with a timer or humidistat -there are relays that apparently do just that sort of job - basically, I'd like to get one of these "boxes"...connect the red and black 12v wires on one side and the 240v source and load on the other....where can I find such "boxes"? Any advice how to use them?

 

[westie101]

Something like this?

http://www.maplin.co.uk/round-base-10a-relays-2567

 

[xelaris]

Something like this?

http://www.maplin.co.uk/round-base-10a-relays-2567[/QUOTE]

thanks for the link...I guess this might do the job but right now I'm pretty clueless on how to use/connect this stuff - for that price I might just buy and experiment a bit...I might connect the red and black 12v wire from the shower cubicle on the right places (if I find them) and a light bulb on the other.
Now, I must have a basic electronics manual somewhere...

 

[EFLImpudence]

I am not sure if a relay is classed as electrically separated which the switch must be.

 

[xelaris]

I am not sure if a relay is classed as electrically separated which the switch must be.

what do you mean by "electrically separated"? Electronics isn't my cup of tea - please let's keep a "basic-electromoron" lingo...

Meanwhile...I've landed into this:
http://www.ebay.co.uk/itm/DC-12V-LC..._Measurement_Equipment_ET&hash=item1e72bb882c

boy, that look simple...12dc on one side and power on the other and there is a timer too?! How far am I going from my project? Can this be connected to the switch inside the shower cubicle to turn on/off the 240v fan?
Of course the timer/relay is installed in the loft next to the fan - the 12v cable is long enough to get there...

 

[viewer]

At some point your original shower cubicle must have a transformer to give 12V to the fan. It seems wasteful to use this just to power a switch; could you use a pull switch (230V) in the bathroom, an external switch or a humidistat and so avoid the complications?
The idea of a stronger fan in the bathroom than the shower could cause problems as hot, moist air would be pulled from the cubicle and, despite the bigger fan, is likely to condense on colder surfaces in the room.

 

[xelaris]

At some point your original shower cubicle must have a transformer to give 12V to the fan. It seems wasteful to use this just to power a switch; could you use a pull switch (230V) in the bathroom, an external switch or a humidistat and so avoid the complications?
The idea of a stronger fan in the bathroom than the shower could cause problems as hot, moist air would be pulled from the cubicle and, despite the bigger fan, is likely to condense on colder surfaces in the room.

The transformer does a lot more than simply feeding the fan....there is a radio, led lights, audio connectors, massager....
I thought about the humidistat...still, the shower has a steam facility and you don't want to get the fan taking away all that precious steam - it's ok for a simple shower....
The pull cord? It's so passe' - you'll have this thing hanging inside the cubicle or even worst you'll need to get out of the cubicle just to operate it? by having the switch inside the cubicle you can stay warm for a while listening to the radio and getting ready and dry...
All I'm doing is simply using the internal switch for another more powerful fan....

 

[Scoby_Beasley]

I didn't find this link btw!!

http://www.taptilecontrols.com/bathroom/index.htm

 

[EFLImpudence]

what do you mean by "electrically separated"?

In a relay there will be no insulation between the 12V and 240V circuits.

So your switch wiring will not be SELV - Separated Extra-Low Voltage - therefore not allowed.

 

[DaftPunk]

Could you feed a 230V relay via a 230V to 12V isolating transformer fed in reverse?

 

[xelaris]

I didn't find this link btw!!

http://www.taptilecontrols.com/bathroom/index.htm[/QUOTE]

Very cool indeed....but I wouldn't dare to check them prices...surely, the technology has been available for ages...still we are stuck with a market which is too slow to understand we have plenty of other choices than pulling dangling strings inside bathrooms?! Not to mention to having to deal with all those Regs checks and limitations? Who's keeping down the evolution of domestic lighting? Greedy professionals perhaps?

 

[EFLImpudence]

Who's keeping down the evolution of domestic lighting? Greedy professionals perhaps?

For some reason the Government doesn't want you to kill yourself.

Me ...

Do whatever you want.

 

[xelaris]

Could you feed a 230V relay via a 230V to 12V isolating transformer fed in reverse?

please, do you mind decode that for us commoners? (ok, I'm back to the GCSE electronic papers left on the loft).

 

[xelaris]

Who's keeping down the evolution of domestic lighting? Greedy professionals perhaps?

For some reason the Government doesn't want you to kill yourself.

Me ...

Do whatever you want.

the killing is the money made from of all these blockages and regs checks - which would not be needed (most of them) if 12v were made more available - innit? Just greedy pro don't want that cos' they'll lose - and we all are kept in the dark - literally.
The flashy technology seen on that link could be available for much less...instead it's a niche only for the well off - like a form of taxation to be paid for keeping the old regime going....

 

[DaftPunk]

A proper wire wound transformer works both ways. If you supply a 12V - 230V transformer with 230V it outputs 12V. Conversely if you feed it with 12V it outputs 230V.

As long as your existing 12V supply is AC, You could feed this into an isolating transformer to switch the relay coil to switch a 230V fan etc.

As the relay is fed through an isolating transformer, even if the relay fails catastrophically and the switching voltage ends up on the coil supply, all you'll get at the shower is a maximum of 12V which is deemed to be safe.

Something like this coupled with a 230V relay and base would do the trick.