I think you can take a look at this Adjustable DC Current Sensor Switch. https://www.amazon.com/Adjustable-Current-Flameproof-Sensing-Normally/dp/B09NZ98X63

Its an AC current transformer, no good on DC or anything >60Hz. Plus it would need to be on only one wire of the twisted pair and that would be like putting a ferrite bead on a power cable - to block RF signals... that'll work well, not!

OK.
What about GND and any of the other lines? Can they be used without causing interferences?

Well the HZ lines are the bell push connection from the front door. Clearly there must be a voltage across them in order that the push works. Presumably that voltage comes from the BUS so maybe one of them has a voltage relative to ground that vanishes if the power goes off. Unfortunately, it will also do so when the bell push is pressed and you probably don't want your UPS switching over every time someone rings the bell - so that means introducing a few seconds delay before activating, exactly what you don't want for a UPS if you want to preserve your work in progress....

 

Personally I don't see why its needed. If the power in the apartment goes off the UPS kicks in. Its but a moment to go out of the door and see if the communal lighting on the landing is working and check the same on an adjacent floor to determine if the outage is apartment, floor or building related.

 

thats a g

OK, the unknowing and uneducated here - - - but what's going on with SA and GND? Is there any kind of signal there? According to the posted document there should be 12V @ 50mA (MAX). Can you get any kind of reading there? If so - and again, "unknowing and uneducated"

thats the good question, and i was also wondering for what a reason SA/GND is there, and decided to try to measure V there,
but i am not able to measure there anything. no idea why. i tried to measure DC.

edit2: ah i just saw its active only in case someone press the bell.

as

Personally I don't see why its needed. If the power in the apartment goes off the UPS kicks in. Its but a moment to go out of the door and see if the communal lighting on the landing is working and check the same on an adjacent floor to determine if the outage is apartment, floor or building related.

Assume you are not at home.

 

Assume you are not at home.

I take it you have an app on your phone ? ? ? If someone comes to the door while you're away - just like RING Doorbell Systems. But if power is out - you don't know if someone came by. Perhaps it's notification of deliveries maybe ? ? ? And if you're away and power fails - how do you know? Do you have a camera in the house pointed at some indicator?

Personally I don't see why its needed.

Neither do I. If someone comes to my door and I'm away - I can't come to the door. So it changes nothing for me. But I'm sure you have your own reasons for wanting this system. Most of us here have already wondered how you wouldn't know if power was out when you were home. I guess nobody thought about the possibility of an app on your phone.

 

hi,
okay the reason why i am trying to solve this case has nothing with delivery/ or someone come over and ring the bell.

I am running some complex HW ecosystem and traveling a lot. For me its critical to figure out if the power outage is inside the flat - ie serious issue on my side, or its central ie whole buidling/area/city is off. Based on that i have to decide what to do with running Virtual machines etc etc etc.

Maybe this is the great point " Do you have a camera in the house pointed at some indicator? ... " ie to point some camera to indicator ie LED on that doorbell, the critical path here is ... will the internet connection work ... to be able access it remotely, i only have failover from optical internet to 2G sim, so to access camera stream its not gonna be an easy task

That's why i initially thought i can somehow intercept DC (voltage) directly on main bus of the doorbells.

thx

 

okay and one more idea:
As there is a red led diode on the doorbell (with monitor) it means that electronic components inside (led, display in case someone is on line) have to be powered from BUS/BUS, correct?

What about to source some Signal/voltage directly from the led diode inside the doorbell?

thanks

 

You cant open the box, its not his and probably tamper-proof anyway

 

It was not until post #25 that we were given any solid details about the system. So again I suggest a voltage presence monitoring Measuring between terminals.
BUT now the question: Why would somebody switch off the circuit breaker for the doorbell/ visitor announcement system??? My solution would be rather different: Monitor the doorbell mains power with a normally closed relay. When the power is switched off two things happen: A security camera takes a photo of the one who switched it off, and the relay contacts close, powering a LOUD ( at least 95dB) electric bell to start ringing.

 

You cant open the box, its not his and probably tamper-proof anyway

i dont get it ... i can open it .. no tamper proof...

BUT now the question: Why would somebody switch off the circuit breaker for the doorbell/ visitor announcement system???

no, in case there is blackout ie full house, block, city is w/out electricity - no powere - doorbell main Bus is dead.

My solution would be rather different: Monitor the doorbell mains power with a normally closed relay.

how do u want to do this? doorbell mains power is not there,,, only BUS/BUS where is DC 30V (what i measured)

 

You probably cannot legally touch it, as you don't own it. Are you renting or leasing the apartment?

OK, here's an idea... but first we need to know if there is a voltage between the HK lines, or on one of the HK lines to GND. Assuming yes, and assuming it goes away if the main property CB drops out then we have a (relatively) non-invasive point of monitoring - though the legal position is still an issue. Now, knowing a delay of a few seconds or so isn't an issue we could use that to send a text message to the TS if the voltage drops out for, say, a minute, and again if it comes back. An MCU with a GSM card running on batteries which are kept topped up from the mains would do that easily

 

You probably cannot legally touch it, as you don't own it. Are you renting or leasing the apartment?

its my place and i paid for that doorbell which is inside my flat and documentation to it was shared.

though the legal position is still an issue.

pls ignore legal... this is not UK, Germany just one of the rubbish eastern EU countries.... and tripping CB was provided for a sake of simplicity, noone will trip CB, no power -> no electricity -> doorbells system is dead.


whats HK/GND? U mean BUS/BUS?

 

If the apartment is like those I have seen in the US, each unit has it's own breaker panel. It should be simple to access the feed to that panel and sense that voltage is present, or not. Two neon bulb-resistor devices with fiber optics exiting the panel. Loss of power at that point is not an internal apartment issue. The life of the neon bulb indicator is usually at minimum 20 years, often much longer. The fiber optic light to the sensor avoids shock and fire issues.

Of course, if the TS paid for the system then getting into the box should be OK.

 

i rather go by a way to intercept directly from the doorbell if possible - somehow

 

When my power goes out I look outside to see if it is me alone or the whole neighborhood.

 

Then use an ISOLATED, battery backup equipped, voltage sensor to monitor the bell circuit. That should be the solution.

 

When my power goes out I look outside to see if it is me alone or the whole neighborhood.

That deos not work if you are not at home or in the area..

 

Then use an ISOLATED, battery backup equipped, voltage sensor to monitor the bell circuit. That should be the solution.

Could you pls elaborate a bit more? Thx

 

A "voltage sensor" can be as simple as an FET input op-amp used as a comparator, driving a single transistor that is powering an opto-isolator. A fairly high value resistor may be used in series with the sensing input, and an adjustable voltage divider feeds the other input. When the sensed voltage This may also be adjusted to signal the loss of a voltage. It uses the power supply negative as the reference level. The higher voltage can be monitored by using a voltage divider with the input.

 

I don't think i am in the position to design it by myself.

 

whats HK/GND? U mean BUS/BUS?

No, I meant what I said. HZ/HZ is the wiring to the bell push button at the front door to the block (and maybe outside the apartment door too). Its a simple switch contact. For that to work there must be a voltage across the contacts, or between one of them and GND. Typically this will be 3v or 5v but might be higher. The assumption is that is derived from the 30v and therefore is a safe proxy for it. The downside is that it will also vanish if someone presses the bell push. However since that's a relatively short process, a few seconds maybe, we can distinguish between a press of the door bell and a power cut by simply waiting to see if it lasts longer than, say, 30 seconds.

So take your voltmeter and measure across the HZ contacts and also between each HZ contact and GND, record what voltages you get. Then get someone to press your door bell and see what happens to those voltages. Finally, if you can, validate they also vanish when the 30v vanishes.