Bluetooth is a good way to connect devices that are near each other. However, it can drain batteries which is one reason Bluetooth Low Energy — BLE — exists. [Drmph] shows how easy it is to deploy BLE to make, in this case, a doorbell. He even shows how you can refit an existing doorbell to use the newer technology.
Like many projects, this one started out of necessity. The existing wireless doorbell failed, but it was difficult to find a new unit with good review. Cheap doorbells tend to ring spuriously due to interference. BLE, of course, doesn’t have that problem. Common BLE modules make up the bulk of the project. It is easy enough to add your own style to the doorbell like a voice announcement or musical playback. The transmitter is little more than a switch, the module, a coin cell, and an LED.
It is, of course, possible to have a single receiver read multiple doorbells. For example, a front door and back door with different tones. The post shows how to make a remote monitor, too, if you need the bell to ring beyond the range of BLE.
A fun, simple, and useful project. Of course, the cool doorbells now have video. Just be careful not to get carried away.
“Cheap doorbells tend to ring spuriously due to interference”
Yes. I bought one from the Lidl many years ago. It lasted a week. It kept ringing at random times but no one was ever at the door. After a week I took a hammer to it. That did fix the ringing and my frustration.
After that I’ve been using two of these (front and rear entrance):
https://frenck.dev/diy-smart-doorbell-for-just-2-dollar/
After maybe 4-5 years I can say that this is incredibly reliable. Probably the most reliable part of my old home.
Wouldn’t be too hard to capture a press with a hackRF and replay it.
I wonder if you could even just generate the right packets given it’s usually just an ID.
We actually have a battery-less wireless doorbell. I don’t know exactly how it works, but the fact that we no longer have to replace the button battery has been a huge plus. The button takes quite some effort to push, so I guess it builds up enough energy with that and uses that to send out a pulse on a certain frequency.
So far we haven’t had issues with false rings yet, and we’ve had this for a few years now.
No more false rings is what I understand… But how sure are you that you never missed a ring?
After all, a doorbel that never rings also never rings false. Just a thought.
I guess you depress a piezo electric crystal and the mechanical energy is converted into enough joules to drive a small packet over the “ether”. If it wasn’t explainable by first order principles, it would sound like magic. Honestly I have no idea how efficiently such devices already can operate. But then there are people who CW with milliwatts over the Atlantic in ham radio.
Yes, ours works very good and reliable as well without any battery in the outdoor switch.