Bathroom switch - via relay?

You can do. FWIW though 4x AA batteries cost about the same and hold a lot more charge. PP3s are especialy bad deals in terms of energy per cost. And C cells are much better than AAs...

You could use a switched mode wallwart, one of the small light ones used for charging a mobile would be about right. No few watts wasted.

Pete Verd> No - in mine the primary side of the transformer would be on all the

yes, it has to be that way

You probably wont want to, but you could use the fan rotor from a 1" laptop fan as your press switch button. It would get the message across in a cute way.

Re the proposed sign, 3d plastic turds are very easy to make. Let a can of foam dribble the right amount out, it will fall/form like a turd, and paint brown when set. :) Or not.

It could. That's true anywhere mains and LV coexist. A good method to strongly discourage it is to have the 240v come in at a position where the wires arent long enough to reach any low voltage part, make sure theyre cord griped on entry, and cable tie L&N together so that if one comes off it cant move far.

Grip & tie the LV wires similarly so they cant stray over to the mains bits.

Then you can earth the secondary side as an added precaution.

NT

Condensation/ damp may still affect it eventually. Picking a switch with gold plated contacts would eliminate the main deleterious result.

NT

I've often wondered about that - what are the crireia when designing a torch, kids toy, whatever as to which size & number of batteries are best?

Hmm, interesting. I don't know much about batteries, so I just picked PP3 as the kind of thing that tends to hang around long-term in smoke alarms and the like.

Unfortunately I've now built the box with a PP3-sized space in the lower-voltage side, so I think I'll stick with it. If I find it needs changing too often I can always stick a holder for four D cells to the wall next to it, like an old-fashioned doorbell.

I've had a bash at actually making the thing, and what I've done is to glue a plastic partition across the box - one half 9v, one half 240v. The relay is glued into a hole in the partition, with the 9v half in the

Interesting - not sure what you mean here. Just tie one leg of the connection to earth, on the grounds that it won't make a complete circuit with the battery? What about the other leg - I can't connect them both to earth or I'd be connecting them together.

Cheers,

Pete

As with many things there are 2 very different definitions of best... Best in terms of run cost favours large expensive batteries that last a very long time. 6v Lantern batteries are a good example. Best in terms of lowest toy mfr cost and smallest size (cute factor) favours small batteries that die quickly, often AA cells (or worse).

Re voltage, lower means shorter battery life and more trouble from poor contacts. Higher means longer battery life but higher battery & battery holder costs. Some circuits are to some degree voltage specific, which overrides other concerns. As to why they're voltage specific, thats getting into circuit and IC design, which is a tad complex.

NT

If you ever need to, a PJ996 might be easier to handle. 9v relays will run on 6v.

sounds like a very effective solution

Just tie one of the transformer LV outputs to earth. If mains meets that side of the LV supply, the fuse/mcb will trip. If mains meets the other side of the LV circuit, the transformer secondary will be low enough resistance to allow overcurrent, and hopefully blow the fuse or trip the breaker, simultaneously frying the relay. You cant earth both of course :)

Someone else can hopefully remind us all of the regs on SELV, which might say something else.

NT

Dunno if any of the home easy stuff would be of use? A switch/dimmer module in ceiling controlled by a battery powered light switch on the wall? Less risk from wet fingers then...

No experience of them though - they might be crap for all I know :)

Darren

Um - what transformer?

Presumably the same would apply with the battery though?

I'd wonder about the current-carrying capacity of the wiring on that side, but I guess it would last long enough to trip an RCD.

Pete

Not especially. They altered them with the 17th edition (deleting Zone

You need to use common sense really - a large bathroom with the switch well away from the wet bits might be ok. A smaller one or one with a massive shower that will generate loads of steam, would be better with a pull switch.

Basins do not really count. Shower trays and baths do.

Pull switch then...

oops make that a "timer fan" rather than a wood one!

The problem with that, is that the timer duration will probably not be long enough to reduce the humidity completely. With a humidistat it may need to run the fan for 40 mins or so to dry the room to normal levels.

Yup panels that need tools to get past count as if they are out of the room. Obviously you don't want water getting under panels for all sorts of reasons, so not getting your electrics wet is just another on the list.

In general the smaller the battery the larger the cost per amp hour - although economy of scale comes into this too. But perhaps the worst is AAA against AA - they're often the same price despite being about half the capacity. PP3s use 6 AAAA - not a common size on its own so difficult to compare.

ummm :)

yes.

It might not, but thats still a big improvement on it definitely wont. Mind you in this case if there's no exposure of the LV side it may be better to leave it uneathed and just equibond the push button front. (Mains to the battery would be fun)

NT

There's no need to flush the toilet every time someone has a wee.

Daniele

Maybe not, but I at least am in the habit of doing so, and I'm not going to tell my lodgers that they shouldn't.

Pete

I guess it's easier to manage this en famille (especially when 50% of the famille is prepubescent boy, and still wholly unabashed by bodily functions).

Daniele

One, totally orthogonal, thought is to have a heat recovery fan running all the time. Needs no particular switchgear.

I'm considering one of these:

The message from Derek Geldard contains these words:

Have got a similar one in Lidl and have it on the upstairs landing. Agree that it's an excellent idea and gives plenty of light to see one's way around.

Hmm, that's quite an interesting idea. I must admit, I was thinking what a shame it was to blow all that lovely heat out of the house just to get rid of the water. Not sure why I'd run it all the time - even at 80% efficient it would still be spending all day pumping heat out of the house compared to if it were turned off. Plus the running cost of the fan itself. I guess that's necessary ventilation if you live in a modern uber-insulated sweat-box, but my house, while not ancient, doesn't really qualify.

Plus the fan has a dangly pull-cord on it, which looks really tacky :-).

And it's not cheap.

But still worth considering, thank you.

Pete

Couple of practical points - don't place a push button within reach of 5 year old sitting on toilet - pp3 will die quickly. I found that my cheap fan only ran for about 10 minutes after "blipping" the light on, even when the timer set for a nominal 20 minutes. It seems to require a connection of about 4 seconds to charge the capacitor fully.