CAN I MAKE MY 1960S FRIEDLAND DOOR CHIME STAY ON FOR A DELAY AFTER PUSH IS RELEASED?

[Carl Haworth]

Our old Friedland chime all too often now emits a only faint "ding"- because the person at the door (usually a delivery driver) just "dabs" at the button.

It works from three buttons:-

Outside of porch; inner front door (the outer front door when the house was built); back door.

The buttons and the chime are in fine working order. Provided a button is pushed decisively, not hesitantly, and held In for at least a couple of seconds, the chime sounds really loud and clear. We can hear it from anywhere in the house.

But we keep missing deliveries when we don't hear a single feeble "ding, and have to rely on a calling card being left to know that a delivery has been attempted - and where the (usually) parcel is.

The chime runs from a Bakelite-cased transformer supplied by a 6 Amp lighting circuit, so the supply is almost certainly ULV AC. I seem to remember that it is 20 V (so it may be a tiny bit less now that we are supposedly on 230 mains voltage),

Is there a button with a damped return spring action which keeps the circuit closed for a short time if the button is released too quickly? (I haven't been able to find one.)

An American video shows fitting a diode across the bell push terminals. That seems to do the trick (how?), but for DC only.

Other suggestions involve a relay with a timer which keeps the output on for a chosen time after the push is released. But, again, this would be for a DC supply only, wouldn't it?

Suggestions would be warmly welcomed. The chimes are melodious, as well as loud. They are far more pleasant acoustically than my neighbour's electronic chime, so I don't want to scrap the Friedland unit and replace it by a wireless device which, at least in my neighbour's house, is visually intrusive - as well as out of character with our interior. That is a lesser consideration, but certainly is a consideration if an electronic device does not give such a smashing sound as our old chime!

I could replace the old transformer with one which rectifies as well as transforms, but the chimes unit is presumably for AC, isn't it? If that proposal would allow the chime to work OK I could try the American idea with a diode. However, I'm curious to know how shorting out one side of the DC circuit to the other side makes the bell stay on for a short time after the push is released.

 

[James]

the short answer is yes it can be done.
not knowing exactly how the door chime works, it would be possible to build a separate 24v dc circuit that uses a timer relay to trigger the existing door chime.
i would expect the timer relay to be about £30 and a dc power supply about the same cost (it may be possible to get an ac timer relay but most work on 24v so i could not guarantee it would work ok with only 20v)
by the time you have costed a timer relay, dc powers supply, enclosure and someone to do this conversion i would expect the cost to be in excess of £200.
it may be simpler to buy a new doorbell.

 

[Carl Haworth]

Thanks for that, James - and for your "brutally realistic" cost/benefit analysis! Of course that makes sense.

The transformer is a Friedland and marked, unsurprisingly, 220 - 250 V AC. Underneath that is marked:-
3-5-8 V.

I would have to test the output to find if that line of voltages simply avoids repeating AC, or if it implies DC. You will probably know which it is by the three possible outputs.

However!

Even if it is AC, that could be rectified with a bridge rectifier, and then a relay with a timer could be used.

The snag is that the relay coil would have to be on the switched output from the pair of pushes for the front of the house, which are in parallel on the same output. The contacts would be on a constant live.

I think that there is a constant live to the chime unit and constant lives to the pushes, not vice-versa.

If this is so, then the relay contacts would need a constant live ex the transformer and the switched output from the front pushes would switch the relay on/off.

Before I thought more about this question I had assumed that the relay and timer could be on the main house circuit board, next to the chime transformer.

That's clearly not so. They would have to be adjacent to the chime unit. Hopefully they could be housed in a bland enclosure close to one of its sides.

I'm more put off by this than by the cost! I like to preserve in working order old technology - especially if makes an agreeable and effective sound. But I like it to look right, too!

A much simpler solution might (might not) be the American man's DIODE. You did not comment on that.

I don't find it a convincing demo. Don't understand what problem he has cured. Careless electrically, too.

 

[brianmoooore]

Small relay with a DC coil of high resistance. Arrange relay contacts to trigger chime. Switched AC feed from door push to bridge rectifier feeding coil of relay, with an electrolytic capacitor across coil as well.
Door push will operate relay and charge capacitor. Relay contacts closed, sounding chime.
Door push released, relay will stay pulled in until the voltage across the capacitor decays to the relay's minimum holding voltage.

 

[James]

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This popular 1-15 Second Delay Press to Exit Button Timer Relay is one of thousands of products held in stock. Call our Manchester based office on 0161 4137939 for more information

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[MFS Electrical]

Perhaps a nice engraved brass plate above the bell push that says “push and hold” sometimes the more simple the solution the better.

 

[Carl Haworth]

Perhaps a nice engraved brass plate above the bell push that says “push and hold” sometimes the more simple the solution the better.

 

[Carl Haworth]

Yes, of course, but the door stile is only 40 mm wide so the sign would have to be narrow and tall to get, in a reasonable point size, my intended message. That would be:-

PRESS
AND
HOLD
FOR
THREE
SECONDS

Centred.

That would not be a good layout. With a much wider door stile the plate could be wide enough to show the same message in two lines (2 x 3 words), still with a large enough point size.

I would want to include a maximum time to avoid some clever-clogs ringing continuously until I made it to the door!

 

[DPG]

Yes, of course, but the door stile is only 40 mm wide so the sign would have to be narrow and tall to get, in a reasonable point size, my intended message. That would be:-

PRESS
AND
HOLD
FOR
THREE
SECONDS

Centred.

That would not be a good layout. With a much wider door stile the plate could be wide enough to show the same message in two lines (2 x 3 words), still with a large enough point size.

I would want to include a maximum time to avoid some clever-clogs ringing continuously until I made it to the door!

Only needs to say:

HOLD FOR
3 SECONDS

 

[Carl Haworth]

1-15 Second Delay Press to Exit Button Relay | SSP Direct

This popular 1-15 Second Delay Press to Exit Button Timer Relay is one of thousands of products held in stock. Call our Manchester based office on 0161 4137939 for more information

www.securitysafetyproducts.co.uk

I've tried pasting in the URL starting at http and ending at .php, but nothing comes up. I've gone to the SSP website, but 'call point push buttons' in Search does not bring anything up.

 

[James]

the blue bit at the top is a clickable link

 

[Lucien Nunes]

If you are still interested in this, what are your electronic construction skills? I would do it exactly as @brianmoooore suggests, for which the parts cost would be about £4. The finished project would be about the size of a matchbox and would need to be at the chime location. This assumes a 2-core cable runs from the transformer to the chime and a separate 2-core cable from the chime to the button. We would need to know which transformer voltage the chime uses, and whether the pushbutton is illuminated.