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.
Bob the builder, username doesn’t checkout. 🔨
If it’s like the ones you find in shops round here, Just use the DIP switches to change it from the default ID that all your neighbours have theirs set to! Or if it’s not got DIP switches then you didn’t pair it, and the receiver paired to someone else’s next time their doorbell rang.
But you may have different ones locally.
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.
Because people would knock on the windows if the doorbell didn’t work. As we experienced with the battery based one.
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.
Yup, I’ve got a couple of light switch remotes which work like that. Slightly clicky but you wouldn’t realise they were different unless you knew. Highly recommend them.
Yes, ours works very good and reliable as well without any battery in the outdoor switch.
“a battery-less wireless doorbell”, so… a bell? 🔔
That’s what I was thinking also.
On the student club at the University, we just had two screws with the wires a little apart in the doorframe. You had to brdige it with a coin or something else conductive, that would ring the bell. If you couldn’t figure out how to ring the bell it was not the place for you apparently;)
With a bit more effort, you can make the battery last decades.
The remote module uses a physical button and has no responsibilities until the button is pressed, so the there’s no reason to power anything under normal conditions. The ring button connects power, triggers startup of the BT module, sends the ring indicator, perhaps gets confirmation if you’re into the whole “reliability” thing, then powers itself back down, disconnecting the battery again. Requires a bit more hardware on the board to handle power switching, but there’s been thousands of projects that do this so it’s easy enough to find.
Using low power sleep modes on the uc can come pretty close to the same result, but using an existing beginner-friendly module board without some extra power control usually introduces enough leakage current to drop your many years of runtime to just a few at best.
You’re ignoring the self-discharge of most batteries. Most CR2030 cells will be dead well within a decade even if they’re unused in their packet. There are chemistries which last better, but finding batteries that last is harder.
20 microamps in standby? Good grief, why so much?
It’s not hard to get a lowly Arduino Pro Mini to sip (much) less than a microamp (I’ve had one running a thermometer on a battery for coming on 7 years and still going).
Why is this thing such a power hog?
nRF52832 is a dog, look at the multiple major erratas and silicon revs despite it being around for 10 years! It’s at 47 pages now, the errata. Very scary.
https://docs.nordicsemi.com/category/nRF52832-category
Since when did doorbells become wireless devices? European homes usually have a 12v AC for the doorbell, Americans have homes made of cardboard so I don’t see the point in not just sliding trough a cable. A doorbell is not something you move so why wireless?
Sure I saw some devices for temporary situations where there is no cable or it was broken, but I rather would prefer a string pulling a switch to a buzzer than that digital cripple to literally just get a sound