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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.

Build

Here’s a quick demo..

clip

Notes

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

Receiver:

  • 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

Transmitter:

  • 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.

scope_inbound_pulse

Circuit

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.

Breadboard

Schematic

Testing on a breadboard:

RFDoorbell_bb_build

Antenna

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

Construction

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)

build_rx_1

build_rx_2

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.

build_tx_1

Credits and References

About LEAP#522 RadioOpAmpLPD433Music Chips
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 my personal collection of electronics projects, 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 (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.