#522 Remote Doorbell
A simple doorbell using a 433MHz transmitter/receiver pair for remote signalling, and an HS-088 sound chip for a doorbell effect.
Here’s a quick demo..
I can’t hear my doorbell when I’m in the workshop, which often means an extra trip to the post office when I miss a bulky aliexpress delivery.
This is a quick build of a wireless doorbell using:
I decided not to use any encoding over the wireless link, so I’m using it more like a spark-gap transmitter. So far in my experiements, I’m not seeing enough interference to get false positives ringing the doorbell. If that changes, I’d probably add an ATtiny and run a simple ASK signal over the connection. We’ll see how this goes..
RF Module Specs
- Model MX-05V
- Working voltage : DC5V
- Quiescent current : 4MA
- Receiving frequency : 433MHZ
- Receiver sensitivity : -105DB
- Size : 30147mm external antenna : 32CM single core wire , wound into a spiral shape
- Product number : MX-FS-03V
- Transmission distance : 20-200 meter ( different voltage , the effect is different )
- Operating voltage : 3.5-12V
- Dimensions : 19*19mm
The incoming signal (DATA pin output) looks like this when the doorbell is pressed. The positive pulse is a fixed-width signal on incoming data. The pulse goes to 0V and stays low for the full duration of the incoming signal.
The transmitter is configured to power up and send a signal when the doorbell is pressed.
The transmitter uses an opamp to perform a peak-detection on the incoming signal to identify a doorbell press, and then fire the HS-088 module.
A speaker is connected with R2 selected between say 0-47Ω depending on the desired volume.
Testing on a breadboard:
For good reception over about 30m with a few blocking walls and doors, I found the following antennas worked just fine:
- Receiver: 32cm of 0.55mm copper wire wound ø5mm air coil
- Transmitter: 25cm of 0.55mm copper wire wound ø5mm air coil
I put the receiver circuit on a small piece of protoboard and mounted in a probject box with a speaker and a micro-USB adapter (for power only)
The transmitter is powered by a 9V battery. I put a mini-pushbutton on the board for testing, and a JST connector for the doorbell wiring.