Electronics question

Dr.Jeff

True Classic
As many already know I am the full time caregiver for my 96 yo mom, so she's living in the same house. I have a "call" system in the home where she can press a button on a pendant and remote speakers sound a 'chime alarm' - telling me she needs something. In other words it is a one way system to signal me. The speakers are wireless receivers that plug into regular wall sockets, and the pendant is a battery powered transmitter. The button on it activates all of the receivers at once, which can be programmed for the "chime" tune and volume. Unfortunately the system has a fairly limited reach (wireless) for the signal, and the speakers are not loud enough (at full volume) when I'm out on the property or have equipment running. So I'd like to "hotwire" a couple of the receivers to allow two things; 1) keep the receiver located within range but extend a pair of wires from it to a further distance, where, 2) the wires connect to a much louder speaker. But I need some help with how to do this.

I opened one of the receiver-speaker assemblies. It is very simple inside. The 110V supply goes directly to a small circuit board, there are 3 controls buttons (volume, menu up and menu down), then a pair of wires to the onboard speaker. I could not find any schematics for it so I don't know if the circuit board changes the voltage from 110V to something less (I suspect it does). Therefore I don't know what sort of speaker I can attach to the speaker output wires if I splice into them.

Here are photos of what's inside the box (I left them large, click on them to see detail). I'm hoping some of you can look at them and understand what it is, in order to help with the project:

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The red and white wires coming from the bottom are the wall plug. The red and black wires barely showing behind go to the onboard speaker. The onboard speaker says "16 ohm, .25 Watt".

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The three push buttons on the right are as described, volume, menu up and down (for chimes).

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You can see one of the little capacitor cans (I think it is) says 10V on it.

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Here's the little on board speaker.
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It will be easy to clip the two speaker output wires and extend them to a seperate speaker. But what spec of speaker will work? Will I need to add a relay and external amp to power a larger speaker?

Really appreciate any help in doing this. It will be a huge benefit to my mom and I.
 
I think the best approach would be to wire in a jack that you can plug an external speaker/amp into. However, there could be a safety issue because it looks like there is no transformer isolating the circuit from the AC lines. You could use an isolation transformer either between the AC power and the unit's power plug or at the speaker outputs. The first option would be easy because they sell ready made isolation transformers that you can just plug into the wall outlet and it will have one or more outlets to plug your load into.

Another thought I had was to make that unit portable by powering it from a battery rather than the AC line. That would work as long as it is not relying on power line communication to other parts of the system. That capacitor that says 10V on it looks like a filter capacitor for the DC power being supplied to the circuit. If that is the case, you could measure the DC voltage across it to confirm the voltage being supplied. Then, find a battery to connect there and take it for a walk and see if it works.
 

Dr.Jeff

True Classic
Can the lines to the actual speaker in the unit be measured for voltage to determine what the system runs on? I'm thinking if I know the output voltage then I can use a small amp directly from those two (onboard speaker) wires. Sort of like they used to make a "booster" amp for a car stereo system.

It won't help to make the unit portable because one of the main problems is the transmitter won't reach very far. So the receiver unit needs to remain in close enough proximity and extension wires taken from there to a remote (and louder) speaker.
 
Yes, it would be a good idea to measure the voltage across the speaker terminals with an AC voltmeter. If it is in the ~1 to 1.5 volt range it should be able to drive the low level inputs of an amplified speaker. Or maybe hook it to a Bluetooth transmitter and use a wireless speaker. That should be good for about 10 meters. If you go that route, the isolation issue goes away. Actually, as long as the unit has a polarized plug and the wiring at your place is correct, it shouldn't be an issue. Unfortunately, many places end up with the wires flipped so the neutral is sitting at 120V instead of ground potential.
 

Dr.Jeff

True Classic
I was able to measure the voltage at the speaker, around .7 VAC. So I think it should work as a line level input to any amplifier? I found some small circuit board type amps (mono) online for very little money. They have a gain control so I assume they will accept a line level input, but there is very little info offered about it. The nice thing is the small size may even fit in the plastic housing for the receiver unit (pictures posted previously), it has quite a bit of unused area inside. These little amps run on 12V and I have some left over "wall wart" 12V power supplies from old electronic devices that no longer function. Just need a suitable speaker for outdoor use. Maybe even a small PA type loudspeaker (keep in mind this is only a doorbell type chime signal). If everything works the way I think it will then this is a really simple conversion. Please let me know if I'm wrong about something here.
 

Dr.Jeff

True Classic
Thanks for all your input on this. Even if the amplifier idea doesn't work, I can still splice the wires to the onboard speaker and extend them. That way the receiver module can be located indoors where it will get a good signal from the transmitter, but allow the existing speaker to be removed and remounted separately outdoors. That at least solves one problem; currently the receivers work fine anywhere inside but they don't work reliably outside, apparently the stucco exterior walls with "chicken wire" act as a Faraday cage. Although it still won't solve the volume issue (being able to hear it over the noise of equipment). However if the amplifier does work, then maybe even the little existing piezo speaker (in addition to being located outside) might be sufficiently loud. Otherwise a larger speaker could be used. Looking forward to playing with this....yet another learning project with electronics, after my previous failure with the fuel injector pulsing module.
 

Dr.Jeff

True Classic
Not sure. As far as I can tell I followed the schematic to assemble it from the components listed in various instructions. I used a prototype breadboard to alleviate my poor soldering skills. But it did not function. I tried a couple of variations but no success. It is possible one of the components is defective, or I accidently killed one, or I misunderstood the schematic, not sure. After a couple days playing with it I got frustrated and put it aside. Fortunately the components all come in multiples, so one day I'll try making it again with new parts and hopefully a little more skill form that first-ever attempt at doing this sort of thing.
 
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