I’ve moved this into projects because it has both a hardware and a software component.
The knock recognition should be easy to set up, it’s been done many times in the past. You trigger based on vibration detection. The problem is it’s not very reliable in some homes, it just depends on the architecture. At some locations, for example, a passing car vibrates the door enough to set it off. But you can certainly try that part.
The more complicated part is that your existing doorbell may be a momentary switch that completes your existing circuit. If it is that kind of doorbell, then there’s a physical break at that point, and you can’t trigger the chime unless the break is closed.
But there are other kinds of doorbells where the button itself won’t matter if you add a smart device to the chime, past the point where the button is connected.
And there are still others which already have a connection point on the chime To add a second buzzer, and those are very easy to work with.
It just depends on where the physical breaks in the circuit are and how they are wired. It’s possible that you will have to re-wire the existing doorbell button‘s connection to the existing chime in order to create a spot where you can add your secondary control.
So we will probably need pictures of the wiring that connects the button to the chime, and of the chime’s board. But I will leave that to the maker types in the community to discuss further.
For discussion of detecting the knock, just search the forums for “knock.“
So there are three separate parts to your project:
selection and placement of the device to detect the knock
selection and placement of a different device to allow the system to make your existing doorbell chime sound
Setting up an automation to allow detection of the knock to trigger the chime
.1) will depend very much on your local architecture as far as how reliable it is.
.2) depends on how your current button is wired. Your project may require re-wiring the existing button’s connection to the chime. And it may be hard or easy. It just depends on the existing wiring.
.3) should be easy.
I’m just tagging a few people who like this kind of project in case they have any ideas.
@ogiewon @johnconstantelo @robinWinbourne @lmosenko @Darwin @jnewbury2280