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Project Notes

#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

Incoming Signals

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.


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.