1. Home
  2. Hobby Electronics Basics
  3. Low-power transformer - and other stuff

Low-power transformer - and other stuff

Hi,

As part of a bathroom project, I want more sophisticated control of the extractor fan than just turning it on with the overhead light. At present, I'm thinking in terms of a flow-switch on the shower supply (so it extracts steam while showering) and a push-switch (for occasional toilet-related necessity :-) ). Both of these would also involve over-run timer(s).

Since in the UK I can't legally have a mains (240v) switch in the location I'd want (well, except for a high-IP-rating one, all of which are ugly) I'm thinking in terms of a 6-12-ish volt "signal" circuit going down to the switches in the room, and a suitable timer module/relay/etc assembly in the (accessible) roof-space above the bathroom where the fan will be. I envisage a very simple circuit on stripboard or similar, in a project box.

My main question is how best to power the "signal" circuit with minimum wasted energy when not in use. I've had a quick look at small transformers (eg

formatting link
) but don't understand all the figures. Things like "efficiency 30%" and "core losses 1.8W" scare me when all I want to do is energise a relay a couple of times a day - but perhaps these only apply under load? In addition, I'm a little confused by the apparent two outputs - do I get a different voltage across each compared to across both or something like that?

Secondarily, any advice on "chunky" self-contained parts for things like my overrun timers? I don't really want to get into detailed electronics on this project, just slap together big chunks of ready-made functionality on a dumb board. It's electrics more than electronics.

Cheers,

Pete

Reply to
Pete Verdon
Loading thread data ...

"Pete Verdon"

** Core loss will apply with no load.
** There are two identical windings - so you can use them in series or parallel.

The voltage rating will be double in series and the current will be double in parallel.

..... Phil

Reply to
Phil Allison

"Pete Verdon" wrote in message news:4963f346$0$512$ snipped-for-privacy@news.gradwell.net...

Why not replace the single switch on the outside with a double were one turns on the light, the other light+fan ? Cheap, simple, safe, foolproof and uses no power...

Reply to
Steve Sousa

Does your house have an electric doorbell? Maybe you could tap off the transformer for that.

If not, you could buy a doorbell transformer from a local home supply center.

HTH

Reply to
Randy Day

I like the two switch idea, but why not make the light+fan a mechanical timer. Turn it to the time needed. 5 minutes for me, 30 minutes for my teen daughter :-) Mike

Reply to
amdx

have you looked at pneumatically operated remote switches, often the buttons for them aren't so ugly.

formatting link

I think 'core losses' is related to magenetising current and so you pay that all the time. 30% is extra costs while you're using the power.

yeah , there's a number of different ways you can hook them up. basically you can either have two isolated outputs, or parallel them or connect them in series.

and I'm guessing you're wanting DC ad then end...

formatting link

But I'd consider putting an outlet in the ceiling crawlspace/attic and plugging a plugpack DC supply into it,

Reply to
Jasen Betts

I just replaced the switch with a dupllex one and fished a new wire to the fixture.

Have Fun! Rich

Reply to
Rich Grise

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.