Two door bells on one push button switch

[JohnW2]

The clarity has seeped into my gray matter, most obliged. Very interesting postings.

You're welcome - I'm glad that things are now clearer!

The following is an attractive options, as its easy to move the bells about. http://www.ebay.co.uk/itm/Wireless-...439?ssPageName=ADME:X:AAQ:GB:1123[/QUOTE]Fair enough, although I can but repeat the adage which is often seen here - that when 'wired' (anything) is an option, it is usually preferable to 'wireless' - which can sometimes be iffy'!

Kind Regards, John

 

[DIYspanner]

Out of curiosity,

if two transformers coil outputs are connected in a series circuit,

am I right in thinking their respective output voltages will behave in the same manner as two 12V batteries connected in series on an HGV in that both bells will be operating at the combined voltage of two transformer coil outputs ?

 

[JohnW2]

if two transformers coil outputs are connected in a series circuit, am I right in thinking their respective output voltages will behave in the same manner as two 12V batteries connected in series on an HGV in that both bells will be operating at the combined voltage of two transformer coil outputs ?

Provided you connect the transformers 'the right way around' (so that their voltages add, rather than subtract), if the bells are also in series, then the voltage across the two bells will be equal to the combined voltages of the two transformer outputs. However, if the bells are identical, that voltage will share equally between the two bells - so each bell will be operating at the voltage of one of the transformer outputs. ... just as if you had two 12V batteries in series in your HGV and connected two identical bulbs in series across the combined batteries - there would be 24V across the pair of bulbs, but 12V across each of the individual bulbs.

Kind Regards, John

 

[DIYspanner]

if two transformers coil outputs are connected in a series circuit, am I right in thinking their respective output voltages will behave in the same manner as two 12V batteries connected in series on an HGV in that both bells will be operating at the combined voltage of two transformer coil outputs ?

Provided you connect the transformers 'the right way around' (so that their voltages add, rather than subtract), if the bells are also in series, then the voltage across the two bells will be equal to the combined voltages of the two transformer outputs. However, if the bells are identical, that voltage will share equally between the two bells - so each bell will be operating at the voltage of one of the transformer outputs. ... just as if you had two 12V batteries in series in your HGV and connected two identical bulbs in series across the combined batteries - there would be 24V across the pair of bulbs, but 12V across each of the individual bulbs.

Kind Regards, John

Based on what you say, why is it such a crazy idea, if the secondaries and bells are the same voltage, to connect two bell circuits in series ?

I apologize if I continue to seem stupid!

 

[bernardgreen]

Connecting in series will work if the bells do not have interrupter contacts.

Interrupter contacts open when the electro-magnet pulls the hammer onto the bell. The open contacts break the current flow and the electro-magnet de-energises and releases the hammer. The contacts close as the hammer goes back and the cycle repeats.

The interrupter in one bell will affect the current flow in the other bell and the ringing becomes very erratic.

 

[JohnW2]

Based on what you say, why is it such a crazy idea, if the secondaries and bells are the same voltage, to connect two bell circuits in series ?

Although I did use the word myself, 'crazy' is probably far too strong a word. It would be a very unusual way to do it (hence might well confuse someone who subsequently worked on it), but it should work.

Personally, I think I'd probably first try just putting the two bells*** in parallel and apply mains power to one of the units (i.e. just using the bell from the second one) - since it's quite possible that one transformer would prove adequate to operate both bells. Even if that technically 'overloaded' th one transformer, the fact that door bells are never activated for more than a few seconds at a time (at most) would mean that no harm would result.
Edit: *** in view of winston's comment, I should clarify that when I mentioned putting the "bells" in parallel, I meant literally just the bells (the bits that make the sound), not using any other components of (or supplying power to) the second of the units.

Kind Regards, John

 

[winston1]

You cannot guarantee the secondaries will be exactly the same voltage and if they are not you will get circulating currents. Also consider what would happen if one bell set lost its mains supply.

 

[JohnW2]

Connecting in series will work if the bells do not have interrupter contacts. ... The interrupter in one bell will affect the current flow in the other bell and the ringing becomes very erratic.

That is true, and I hadn't considered that potential problem. Do AC-powered bells commonly have interrupters?

Kind Regards, John

 

[JohnW2]

You cannot guarantee the secondaries will be exactly the same voltage ...

Indeed not - which is why I'm not very comfortable with bernards 'anti-phase' approach, which relies on exact 'cancelling' of the two voltages.

... and if they are not you will get circulating currents.

I'm not sure which arrangement you are thinking about here. No-one has suggested (except perhaps the OP, initially) that the secondaries of the transformers should be put in parallel - that could, as you may be implying, be a potential disaster.

Also consider what would happen if one bell set lost its mains supply.

Again, I'm not sure what arrangement you are thinking about. With transformer secondaries in series and in-phase, the worst that would happen would be that the bells wouldn't work - properly or at all. With bernard's anti-phase system, there would be a problem (both bells would presumably attempt to sound continuously, at reduced voltage).

Kind Regards, John

 

[winston1]

You cannot guarantee the secondaries will be exactly the same voltage ...

Indeed not - which is why I'm not very comfortable with bernards 'anti-phase' approach, which relies on exact 'cancelling' of the two voltages.

... and if they are not you will get circulating currents.

I'm not sure which arrangement you are thinking about here. No-one has suggested (except perhaps the OP, initially) that the secondaries of the transformers should be put in parallel - that could, as you may be implying, be a potential disaster.

Also consider what would happen if one bell set lost its mains supply.

With bernard's anti-phase system, there would be a problem (both bells would presumably attempt to sound continuously, at reduced voltage).

Kind Regards, John

The live transformer would feed current into the dead transformers secondary via the bells. This would be reflected to its primary as a voltage up to 240v which would try to power anything else connected to the dead circuit.

 

[JohnW2]

The live transformer would feed current into the dead transformers secondary via the bells. This would be reflected to its primary as a voltage up to 240v which would try to power anything else connected to the dead circuit.

AFAICS, in practice, if both were supplied from the same circuit, the only way in which one, but not the other, transformer could lose its mains would be be for an interruption to arise in its connection to the mains circuit (blown plug fuse, cable damage or failed connection) - in which case it would not be able to feed back that induced voltage to anything else. I personally think this is probably more of a theoretical than a practical concern.

However, as I've recently written, before attempting any of these 'esoteric' approaches I would ascertain whether one of the transformers was capable of operating two bells, since that would, if it worked, afford the simplest, and essentially non-contentious, solution.

Kind Regards, John

 

[DIYspanner]

I contacted the manufacturer of the bell I was going to fit and to quote their response,


"Unfortunately these are standalone units and cannot be linked with any other chime or sounder."

 

[JohnW2]

I contacted the manufacturer of the bell I was going to fit and to quote their response, ... "Unfortunately these are standalone units and cannot be linked with any other chime or sounder."

It doesn't surprise me that they said that, since they are presumably not designed to be linked, but that doesn't necessarily mean that it can't be done.

I've got a bit confused amidst all this discussion - can you remind me of exactly which bell we are talking about?

Kind Regards, John

 

[DIYspanner]

I've got a bit confused amidst all this discussion - can you remind me of exactly which bell we are talking about?
Kind Regards, John

I'd originally asked if I could fit an additional mains fed, bell push operated bell so that it operated along side an existing mains fed, bell push operated bell off the same bell push. One bell at each end of the house.

I posted my question to establish the best way to wire the bell push circuits together which, from general opinion, seems to be frowned on.


The bell I had in mind was this one for which I contacted the manufacturer to ask their opinion.

http://www.ebay.co.uk/itm/221331099...=1&clk_rvr_id=770490847273&afsrc=1&rmvSB=true

 

[JohnW2]

I'd originally asked if I could fit an additional mains fed, bell push operated bell so that it operated along side an existing mains fed, bell push operated bell off the same bell push. One bell at each end of the house. ... I posted my question to establish the best way to wire the bell push circuits together which, from general opinion, seems to be frowned on.

Yes, I understand that. Of course, at least some of the various 'clever' approaches (particularly bernard's suggestion) that have been discussed (and frowned on by some) would have relied on your having two essntially identical units, so would not be appropriate for adding a (different) new one to an existing one.

The bell I had in mind was this one for which I contacted the manufacturer to ask their opinion.
http://www.ebay.co.uk/itm/221331099...vr_id=770490847273&afsrc=1&rmvSB=true[/QUOTE]
Fair enough. As I've said, it's far from impossible that the transformer in one would be man enough to also operate the chime in another (non-powered) one - but you would only be able to discover if that were the case by buying two and trying.

Kind Regards, John