As far as I know all Shelly 1’s have dry contacts (=potential free) 
But yes,it requires an external power (12-24vDC OR 110-220vAC)
But all relays require power 
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Yep, all the Shelly 1s since the first model have had a dry contact.
If your Shellies don’t support anything other than 230v, then they’re not the Shelly1 (non-PM) version
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Here’s mine…it’s shelly 1PM, and it doesn’t have dry contacts. L and L1 are interconnected, SW is switch, O is 230V output.
Like I said, non-PM version. Only the standard Shelly 1 support dry contacts, because you can’t really measure power if you don’t know your voltage
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I see the problem as being there is no power source at the button. Yes, there’s the 15VAC, but that goes to zero as soon as the button is pushed.
Once there is power, a dry contact shelly will be just fine. The ESP01 with a power supply would work, but you’d have to appropriale enclose the two.
The esp01 with a 18650 battery and charging cicuit could work. The charging cicuit is powered by 15VAC via a full wave rectifier, a capacitor and a 5V regulator. Again, an enclosure. (I really like this idea for door buttons and door bells. because the battery will probably last 10 years and will always be charged! And the battery could be a really cheap one! All without having to run another circuit.)
Actually, you could probably use a large capacitor (10,000µF@6V?) instead of the battery.
Most intercoms have lots of space inside.
On our intercom there is mostly air inside.
I mounted a ESP, an opto coupler (to make is less noisy than relay) and a microphone.
The microphone listens to high sounds and if a boolean is on then it “presses” the button.
This is great when you know you have folks coming, you enable the auto open mode (which disables itself after an hour) and when someone rings on the intercom the door opens.
That won’t work.
The charging circuit will press the button if you connect it in parallel over the button.
Connecting it in series will only let it charge when you press the button
No. Not even close.
An ESP uses quite a lot and is not suitable for battery use.
And lastly, since you don’t know what the power source is of this 15v you can’t just load it with a charger.
What happens if this circuit is not built for any loads at all?
You end up frying the system in the house.
This is not a good idea.
Like I said, non-PM version. Only the standard Shelly 1 support dry contacts, because you can’t really measure power if you don’t know your voltage
i admit, i only use PM versions, so i missed that - by bad (luckily though - good to know!). I do have a couple of non-PM’s, but they are from sonoff and they doesn’t have dry contacts.
The esp01 with a 18650 battery and charging cicuit could work
esp 82xx draws around 70-80mA roughly. So, 2000mAh battery would last one day. Charging is also risky: since shorting those two wires result in electric lock to open that means that you have 15V in series with lock. If you load it lock will be constantly engaged, in best case it will heat up because current will flow through it.
But it also depends on lock type - release current: if it’s high current one (some models draw over 1A when engaged) i guess you could load this output with 70mA constantly. But then you’d end up with “enormous” package of electronics (battery, charging circuit, relay, esp…) you have to put somewhere… and there’s also a risk of “frying the system”, as hellis said.
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I’ve gathered some more info into this mess of wires.
What I know so far:
- Blue & Red are connected to the button with 15VAC between them. (Red is positive)
- As long as red and blue make contact the door buzzes open (when button is held down)
- Gold is my Bell, with 15VAC between it and green, when they make contact my doorbell rings
What I want to achieve: I want to be able to buzz open my door from Home Assistant
I have a Shelly One Plus laying around, which would be great if I can use that, but if it makes more sense to buy an alternative I’m happy to do that.
The Shelly One Plus is Dry contact, so I could power it from elsewhere but ideally I’d like to avoid that as getting power to where it’s needed would be a pain.
I’m trying to find schematics on the wires etc. but the building is 100+ years old so it’s proving difficult
Ideal Solution: To be able to power the Shelly from these 15VAC wires
This ‘might’ work:
Provided:
- The 15vAC has enough power to support the Shelly1
- The capacitor holds the charge long enough. This depends a bit on how long the doorbell is pushed. If needed you can increase the capacitor to 47000µF
That was an unexpected design.
I was expecting a “phone”.
You can’t find these cables somewhere else?
Like a junction box above?
Or in the breaker box?
Hi, I think either the blue or the red will be the ‘hot’ wire and always at 15vac. when the button is pushed, it returns the 15vac downstairs to open the door. With that, you need to determine which wire is neutral in there, so the hot and neutral feed your shelly in aceindy’s schematic. Maybe one of the whites? The bare wire labeled gold I would guess is either ground or neutral.
Why are you guessing?
It has already been posted what the cables are
I doubt there are any neutral wires.
My guess is that you have a live, switch, and signal wire for the buzzer.
The bell might have a neutral.
But as said before. This is not the kind of things you guess and hope for the best.
If this would have been your own dishwasher/fridge whatever, then you are the only one loosing on it.
In this case there is a system that is several decades old and chances are there are no spare parts in your local hardware store.
If you break the things the landlord will get rather pissed.
The red and blue might have 15vac between them with a meter, but one of them is going to be 15vac hot, and the other will return the 15vac to the lobby when the button is pressed. Confirm which one by comparing each with ground. That is not a guess.
The OP’s goal is to be able to power the shelly or other device from the wiring at hand. As he states, sure it would be be easy to power from somewhere else.
One of the connections to apartment buzzer has to be a neutral.
Its not that hard. But to your point there is risk to messing with the wiring and adding devices. I’d add a fuse inline to whatever new is being powered just to be sure.
There is a lot of concern, and rightfully so, for safety. I’m all for that. This means that @NoBadDays739 is going to figure out what the all of those wires are doing.
Here is a hypothetical circuit for the door latch: one leg of a step-down transformer is connected to the soloenoid, the other to the push button; the push button and the solenoid are connected to the other. One could determine the impedance (not resistance) of the solenoid with an AC ammeter. 1A means that the impedance is 15Ω. and 15VA which is a lot for the low power devices described for controlling the solenoid. In older places, this would not surprise me.
15Ω with 100mA going through it (as would be the case of the ESP01/power supply/charging cirucuit/battery) would be 0.15W max. (8 LEDs?)
I suspect that @Hellis81 didn’t understand the circuit I proposed. The charging cicurit charges the battery and powers the ESP01. When the button is pressed, the input to the charging cirucuit goes 0. Thus the battery powers the ESP01 while the button is being pressed. Assuming the button is held for 10 seconds, the ESP01 (at 100mA) consumes about 0.3mAh of the battery. Once the button is released, the battery is recharged. And, this is important, the ESP01 does not get reset. Most power supplies for this purpose further isolate the electronics from the mains. I failed to mention that the relay of the ESP01 is what is “pressing” the button. The ESP01 just needs to be programmed, or commanded, to “release” the button.
Back to the question, “What happens if this ciurcuit is not built for any loads at all?” Great question! The type of transformer used for solenoids and doorbells has a fairly high internal resistance. Putting a load on it, even a direct short, causes the very little damage, if any at all. Not likely to fry the system in the house. If one has these concerns, and they are justified, then one should not be messing with the circuit in the first place.
Again, a source of power for the device controlling the pressing of the button, that is the challenge here.
-osd