Wiring doorbells

[Wowbagger]

My ancient aunt Phyllis is blind and going increasingly deaf. She spends most of her time in the lounge with the radio on and has a doorbell affixed to the wall immediately above her chair. She has another, which runs off the same button, placed in the corridor so that she can hear it if she's in the kitchen.

Recently we replaced the doorbell above her chair because the old one seemed to have given up the ghost. When we wired the new one in, the corridor bell rang non-stop. Dez disconnected it in the hope that the new doorbell would be loud enough for her to hear it from the kitchen. It appears that it isn't.

She wants me to wire up her bell again so that both ring when the button is pressed. I have no idea how - my scant knowledge of physics and circuitry has been decaying ever since it was last added to in about 1967.

Any advice would be appreciated.

[Greenbank]

A 'mobile ringer' that she can carry with her.

[Marj]

We have a cordless one, the batteries didn't need changing for nearly 2 years.

[rafletcher]

A 'mobile ringer' that she can carry with her.

She WILL forget to do that.

[tiermat]

I would forget about the old doorbell and go for one of the cordless systems, we have one that has a battery powered unit, for carrying around, and a plugin unit.

Even I, with my abysmal hearing, can hear it when it goes off!!

[border-rider]

You need to wire the bells in parallel, and the switch in series with them both, if they use the same DC voltage. If the bells operate at different DC voltages, this won't work and you may have a problem. You might have to run multiple wires to the bellpush

Either way, a wireless bell might be easier, as the others said

[Jaded]

A 'mobile ringer' that she can carry with her.

Plus one.

MiL has one of those, it has a flashing blue light on it, which can be seen from across the room.

[rafletcher]

Reminds me of the "Telephones for the deaf" sketch on Not the 9 O'clock News.

[Wowbagger]

You need to wire the bells in parallel, and the switch in series with them both, if they use the same DC voltage. If the bells operate at different DC voltages, this won't work and you may have a problem. You might have to run multiple wires to the bellpush

Either way, a wireless bell might be easier, as the others said

Ah! this throws light on the matter. Thank you.

The old doorbells both used the 9-volt PP3 battery. The new one uses two D-sized 1.5 volt batteries, so we were trying to wire the 9V and the 2*1.5V together, and the higher voltage bell would ring constantly.

Out of curiosity, do you have an explanation comprehensible to ignoramuses as to why this happens?

[jogler]

We have a cordless one, the batteries didn't need changing for nearly 2 years.

with a chimer in the kitchen & another one on the landing so that I can hear it when in the office upstairs.

[border-rider]

Having the higher voltage one in parallel with the lower voltage one  is going to shove current round through both bells even when the switch is open.  

The higher voltage one rings because it's got current going through it the right way.  The lower voltage one has current going the wrong way, so likely isn't very happy.   You're probably charging the 3V battery array up tot 9 V

It makes sense if you sketch the circuit. 

[Wowbagger]

Having the higher voltage one in parallel with the lower voltage one  is going to shove current round through both bells even when the switch is open.  

The higher voltage one rings because it's got current going through it the right way.  The lower voltage one has current going the wrong way, so likely isn't very happy.   You're probably charging the 3V battery array up tot 9 V

It makes sense if you sketch the circuit. 

Thanks. I think we'll just buy twin doorbells. Aunt Phyllis isn't short of cash.

[Panoramix]

+1 to what MV said

The only solution would be to run them in serie with a 10.5V battery and one switch. There is a risk of burning one if the impedances don't play nicely together (or you could experiment by increasing the voltage until the 2 work)

[border-rider]

or you could do something clever with one battery (or preferably a power supply) and a voltage regulator, and keep them in parallel

[Greenbank]

or you could do something clever with one battery (or preferably a power supply) and a voltage regulator, and keep them in parallel

Or a couple of diodes.

[border-rider]

Aye, that's the easiest way: connect a diode in line with each bell, pointing in the appropriate direction.   Cheap & easy

[Kim]

Sounds like what she *really* needs is a pager system.  It might seem overkill now, but think about how she's going to hear the smoke alarm a few years down the line.  The systems are usually modular.

Connevans is a good place to start looking.  They're the SJS Cycles of deaf gadgets.

Doorbells are of course not rocket science, but it's hard to advise in a useful way without knowing how the bell units and power source are wired internally.  What you really want is a pair of electrically identical bells, with the bell/solenoid mechanisms wired in parallel (yes, that requires access that you might not easily have to the internals of a combined battery/bell unit), and the battery/switch only connected to one...

ASCII schematic time:

     Switch
+----/ ----------+--------+
|+               |        |
= Bat            O Bell   O Bell
|-               |        |
+----------------+--------+

Not, as you describe here:

+----------------+----------------+
|                |                |
O Bell           |                O Bell
|+               / Switch         |+
= Bat            |                = Bat
|-               |                |-
+----------------+----------------+

Which is relying on matched battery voltage and polarity preventing current flowing in the series circuit of both batteries and bells.

Wireless doorbells on the same channel would be the easy solution.

ETA: Ah, of course, diodes.  That would work:

       Diode            Diode
+------|>|-------+------|<|-------+
|                |                |
O Bell           |                O Bell
|+               / Switch         |+
= Bat            |                = Bat
|-               |                |-
+----------------+----------------+

1N4001s would probably be sufficient.

[fred the great]

If you wire a number of electrical items in series it results in a power drop each time.

I would suggest one power supply for two or three bells, all wired in parallel. Of course all bells will ring when the bell push is pressed and she can hear them ringing providing she is not too far from any bell.

[Jaded]

Reminds me of the "Telephones for the deaf" sketch on Not the 9 O'clock News.

Now I re-read the OP : Doh!

(That sketch was predated by a student friend of Mrs Js asking her why they didn't get a telephone for her parents that lit up when it rang.  )

[Kim]

(That sketch was predated by a student friend of Mrs Js asking her why they didn't get a telephone for her parents that lit up when it rang.   )

We have one of those (well, it incorporates a xenon strobe).  It's loud enough that I once woke up wondering why I could hear an Epson inkjet printing, when we only have an HP laser.  It was barakta using said phone in the next room to help her mother troubleshoot her printer problems.

[Kim]

If you wire a number of electrical items in series it results in a power drop each time.

Voltage drop, and only if the items are loads and not voltage sources (which add).

Assuming the bells and battery ratings match, this would be a legitimate circuit (note the battery polarity):

            Switch
+---------------/----------------+
|                                |-
O Bell                           = Bat
|+                               |+
= Bat                            O Bell
|-                               |
+--------------------------------+

Which you'll note handily eliminates the need for the diodes mentioned above.  I didn't suggest it because we know the bells don't match, and the wiring might be topographically challenging.

[fred the great]

I was just keeping my answer simple for the non technical reader.

If one connects three light bulbs in series the last bulb will be considerably dimmer than the first one but connected in parallel they will have a similar brightness.

That's about the limit of all my Physics knowledge from yesteryear

[border-rider]

That's about the limit of all my Physics knowledge from yesteryear

Probably as well, because it's wrong.

If the three series bulbs are equally rated then you'll get the same voltage drop across each and the same current through each, so the same power dissipated in each.  Neglecting lost volts in the wiring, of course.

Whether a series or parallel combination is brighter depends on the nature if the source and the impedance of the load. 

[frankly frankie]

Wireless bell seems the obvious solution.

Mind, my neighbours' one rings every time another neighbour (across the road) unlocks his car ...

[rower40]

Wireless bell seems the obvious solution.

Mind, my neighbours' one rings every time another neighbour (across the road) unlocks his car ...

I found out my cow-orker's password this way.  He and I both used the same make of wireless keyboard.  I got in before him, and had a blank Word document open.  His name and password appeared when he logged in on his computer.

I printed it off, and gave it to him, with "Is this your password?" We then agreed that exactly one of us would switch our keyboard sender and receiver to the alternative channel.