Battery doorbell local repeater?

Good morning Tim,

I have a device that is essentially a microphone placed near your doorbell chime 9powered by 4 AA batteries (or maybe AAA) that then transmits to an AC powered ringer that you plug into a convenient outlet. Here is one from Home Depot:

Now this unit is 120V, and I have no idea if you have Home Depot stores in your 240VAC country, but there must be something similar. The pickup units batteries seem to last 2-3 years, and it rarely false triggers, unless I slam the closet door it is mounted near.

Best regards, another Tim

What about installing another light-draw chime just inside your door? Activating the button would trip both. Just put it in series with the bell.

KISS

Peter Wieck Melrose Park, PA

Hi Tim!

The problem is, I don't have a 'convenient outlets' near the front door. ;-(

Yeah, there are a few similar things available over here and even a doorbell that allows you to hook up a conventional wired / battery bell and trigger a wireless one, again, I didn't really want to have anything 'else' if I could get away with a small buzzer / sounder inside the front door. That would help the Mrs hear it as she's normally just the other side of the internal wall in the lounge. ;-)

Hehe.

We had the similar thing again this morning ... I heard the doorbell go but as I was getting up to answer the door, he was knocking on the glass because *he* hadn't seen / heard any feedback that the bell was working.

If I can find a suitable mini-buzzer it may well work in series with the existing bell and so would be very easy to tack into the existing circuit and mount just behind the bell push.

We hear both things, they hear the buzzer. ;-)

Cheers, T i m

Two thoughts, from a mechanical engineer.

1. Cheap solution: write DOORBELL WORKS! on a 3x5 card and tape it to th e door.

1. Also cheap solution: if you're like 90% of people you have a smoke ala rm that doesn't work because you've changed the battery. Take out the litt le piezo speaker and put it on the other side of the door. Wire it to the buzzer. Include the 9 volt battery as needed. (not sure exactly how your doorbell is powered.

I apologize in advance for violating the Terms of Use of this forum, which include to provide the most complicated DIY electronic design project possi ble for any problem that might have a simpler solution.

That was another thought Peter (and was suggested elsewhere), maybe a electromechanical buzzer so they hear the buzzer directly and also any reverberations that travel though the frame etc.

Quite, but the issue with the above is that I'd need to get lucky and find something that would work itself and allow the existing bell to ring, especially when it's already running on a reduced voltage (4.8V of Ni-Mh rather than 6V of alkaline).

That's why I was trying to isolate the existing bell functionality and leech some power off that to run an auxiliary sounder.

Cheers, T i m

Worth a try ... except the batteries do go flat and so the bell doesn't work .. ;-(

I was going to include an LED in the bell push that lights or flashes when they press the button (discharging cap) but again, that's assuming they look for such (and most deliveries are in the day and this would be South facing).

That was the sort of idea of my plan. ;-)

;-)

The thing is, I'm not sure a simple solution works in this situation. What I was hoping for is a 'subtle' (electronically) solution that does what I need.

So, under normal circumstances there will be 6V DC across the open bell push.

I have a cct in parallel with that that charges a cap via a diode and resistor I have a small 'remote' PSU that wouldn't be affected by the bell push shorting it out (because of the diode).

If something could latch and discharge the cap though a buzzer and release once it has, everything else the doorbell will 1) work as designed and 2) the 'repeater' should work without much interference to the existing solution, albeit other than a slightly increased load on the battery.

If I could find a buzzer that works from 1.2V, I could put a couple of fwd biased diodes across it and went back to alkaline cells, that should work and be as simple as it can get?

Cheers T i m

Keeping in mind that this forum exists so that the uninformed may provide t he least appropriate, most complicated, least reliable solutions for establ ished problems with established (and reliable) solutions such that the requ ester of such information may be relieved of taking responsibility to do th e right thing in the first place, over-complication is the natural order of things (Thank you, TImothy).

Put it in a small WireMold box right inside the door by the door jamb. Feed it from the bell wire - take one lead, and connect the buzzer in SERIES w ith that lead. At 58 ma, it will not overload your transformer.

Peter Wieck Melrose Park, PA

I'm keeping out of that one. ;-)

Or I could design / 3D print something. If it were white it could stay as it is.

Yeah, as long as it will fit on the inner frame (inwards opening door) that will be fine. The frame is the same size as the end of the corridor (the door was made to fit the space) so there isn't a lot of clearance on either side for much.

OK.

Well, it's batteries but if the buzzer requires a minimum of 6V and the battery is only 6V, I'm not sure either buzzer or bell will still work will they?

This was why I was thinking of some way of 'phatoming the 6V (battery) psu to the bellpush and using that to source the voltage often required to run these sounders?

I wasn't looking to make it complicated on purpose, I just couldn't see how it could be KISS and still do what I want / need?

Something that could be easily modified is the PSU for the bell itself. The bell sits on the side of the stairs so a small hole though the back of the bell box for a cable to a small 12V battery (sealed Lead acid or possibly a similar voltage diy Li-Ion pack) should be doable. *Then* I have the spare 6V for a frame mounted buzzer. ;-)

Cheers, T i m

On 10/22/2020 12:40 PM, T i m wrote: ...

Thanks for that Bob.

I'm, confused. I asked about one of those (Electro-Acoustic Transducer) on eBay, if it was a speaker or if it produced a noise on it's own, just with a supply voltage etc and they replied it was just a speaker, requiring external driving (assuming I'm seeing what you intended on the link)?

Cheers, T i m

You're right, sorry. Brain fart. These are true buzzers, a couple work down to 1.2v:

Is the doorbell mechanical, with a coil and contacts that open and close? I f so, a speaker in series would make noise from the interruptions in curren t flow. It might be loud enough for your needs. The only way to find out is to test it with any old speaker that you have laying around.

You could put the at-the-door buzzer in parallel with the interior bell. It would require a separate battery & its occasional replacement.

------|>|---+---|

Do you even need any trigger/latching circuit? Often doorbells only make a sound when the button is pressed, so the visitor should not be bothered by that, and it would not require such a trigger circuit.

Why not do pretty much exactly what you already suggested:

Get a big capacitor (perhaps a couple of 1 Farad 5.5V supercapacitors in series, they are quite small and should withstand 6V even without equalising resistors), charge the capacitor from the existing doorbell wiring via a 1N4004...1N4007 diode, and put a piezo or mechanical buzzer connected in parallel with the diode in the direction with the positive of the buzzer connected to the cathode of the diode. During charging, the buzzer will experience 0.7V of reverse bias which probably won't bother it, and when the button is pressed, the diode is reverse biased and the buzzer receives whatever voltage the capacitor was charged to. For simplicity, don't bother with any extra series resistor to limit the charging current, as that would expose the buzzer to more reverse bias, and it is probably unnecessary after the first charging cycle. The capacitor won't have time to discharge much when the button is pressed, which means it won't take long to recharge either. When the circuit is initially installed, it might take a while to charge the capacitor, perhaps a minute or so.

So you need capacitor, diode, buzzer.

If the existing bell has a lot of inductance, when the button is released there might be a large voltage kick across the switch. The diode ought to catch this so I would not expect it to fry the new piezo buzzer, but it might alter the sound of the existing doorbell when it releases.

Hey, I like it, but we can complicate it more. I think we need a Raspberry Pi or an Arduino in the circuit controlling it.

Outside of the programming the Arduino is very simple to use for many things. They can be bought for less than $ 5 from many places in China.

That is often less expensive than many of the relays it would take to do the job.

erry Pi or an Arduino in the circuit controlling it.

I need to learn more about that; this is one of those technical advances th at kind of sneaked by me. I was trying to figure out if I could replace my washer timer with something like that, 30 year old Maytag and can't get pa rts, but then it started working again.

They really really don't make them like that anymore.

They are really simple and inexpensive. For your washer timer one should work fine. They have several inputs and outputs. There are internal timmers you can set the time of. So you input a signal on one pin and start a timer. When it times out, send a signal to one of the output pins. Then start the process all over again with another input and output.

While they will do more, they really excell at things like a minature PLC.

There are some learning kits for around $ 100.

I doubt if there is a part or piece in any Maytag of similar vintage that c annot be found somewhere, and in short order. We have a Maytag dryer at our summer house, and just replaced the belt, rollers, idler and motor with ne w parts (made in Mexico and the USA) all for less than $100 installed (by m e). It was made in 1971.

And for very good reason: 30 - 45 gallons of water per load. Up to 2 gall ons of water left behind (full load) that has to be dried. And more. But, t hey do work well, when they work.

Peter Wieck Melrose Park, PA