This project is a simple BLE door bell for beginners with the option to retrofit an old (broken) RF door bell for experienced constructors. This BLE doorbell, while still running for years on a coin cell, has a number of advantages over the RF alternatives:-

* It is immune to interference from other doorbells in the neighbourhood.

* You can choose your own tune to play when the button is pressed

* You can have multiple monitor/receivers responding to the doorbell press button.

* It remembers when the door bell was pressed when you were out and displays a flashing led.

* You can monitor a front and back door press button with one (or more) monitor/receiver and optionally have different tunes for each door

* You can add up to four (4) extensions to monitor the door bell over the wifi.

* Beginners can safely complete this project by using an encased USB supply and a small plastic box for the monitor/receiver and extensions.

Background

When the existing RF doorbell failed, the first choice was to just replace it with a new one. However over 50% of the reviews of RF doorbells were negative, complaining of interference from other RF doorbells in the neighbourhood that caused the bell to sound when no one was at the front door. We had also noticed that ourselves prior to doorbell failing. So instead of buying a new RF doorbell, the previous BLE Window Open Detector project was repurposed as a doorbell. The components were small enough to fit in the existing push button case and door bell receiver. However you can also use a small waterproof box for the doorbell and a plastic box for the receiver.

This project is also online at BLE Door Bell Retrofit

Components

Prices as at January 2025 excluding shipping.

BLE Door Bell

1 x nRF523832 module such as Jessinie XL52832-D01 nRF52832 module ~US4.90 and Jessinie Test Board Adapter Plate for NRF52832 ~US$1.70 – Total ~US$5.60 (Aliexpress)

                     OR Holyiot YJ-16013-NRF52832

                     OR (in this build) Holyiot nRF52832 – YJ-16048 ~US$5.00 (Aliexpress)

1 x CR2032 coin cell ~ US$1.00

1 x Aokin CR2032 Battery Holder – US2.51 for 10 off (Aliexpress)

1 x PCB or veroboard to suit nRF523832 module (see BLE Window Open Detector for the pcb used in this build)

1 x Momentary Pushbutton (weather proof) – if not retrofitting an existing door bell e.g. Jaycar CAT.NO: SP0732 ~US$4.40

1 x ABS plastic box (weather proof) – if not retrofitting an existing door bell e.g Jaycar CAT.NO: HB6124 ~US$8.70

Door Bell Receiver and Extension (One set for receiver and one set for Extension)

1 x Dfrobot Beetle ESP32-C3 ~US$7.90

1 x Dfrobot Voice Prompt Module with Integrated MP3 Player and Speaker ~US$7.90 OR buzzer e.g. Jaycar Mini Piezo Buzzer 3-16VDC ~US$2.80

1 x USB supply e.g. Dfrobot 5V 1A ~US$3.40

1 x clear plastic box – if not retrofitting to existing door bell receiver. e.g. Jaycar CAT.NO: HB6005 ~US$2.40

The circuit for the BLE Door Bell Push Button is trivial. The circuit above is for a Jessinie module (pdf version)

If you are making your own door bell, you can use any suitable 'bare board' nRF52832 module such as Jessinie XL52832-D01 nRF52832 module and Jessinie Test Board Adapter Plate.

The the coin cell can be mounted on the back of the board between the VCC pin and hole drilled in the centre earth plain. Mount it in a small box weather proof box with a push button and optionally an indicator Led.

Here the existing doorbell was refitted with a BLE module. The existing doorbell button is stripped of most of it components, except for the battery holder, led and its resistor and the main push button. A small nRF52832 module is then added to broadcast “Front_Door” when the button is pressed.

Before removing the components from the existing door bell push button, the doorbell led and its series resistor was identified and the led polarity determined with a multimeter on diode mode. The led and its series resistor is kept when the other components are removed.

Tracing the track on the doorbell PCB gives the layout below (pdf version) Apart from the battery connections (Bat -v and Bat +v) there are only two other connections. One from the push button to nRF25832 pin 2 (A0). The push button connects to the +V when pressed. The other is the output to drive the led indication when the button is pushed. The +ve side of the led is connected to Bat +v, on the pcb, via a series resistor. The negative side of the led is connected to the ble module, either pin 7 or pin 11 as convenient.

In this construction a PCB from the BLE Window Open Detector was used trimmed to fit and pin 11 was used to drive the led. However you can also a piece of veroboard to mount a YJ-16013-NRF52832 module and use pin 7 to drive the led.

Here is the completed bell button PCB wiring (last photo above). Note that the tracks at the bottom of the original push button board have been scrapped off so as not to interfere with the BLE module's antenna,

Install the pfod_lp_nrf52_2024 Arduino board support as described in Easy Very Low Power BLE in Arduino

The sketch is lp_BLE_DoorBell.ino and the SafeString library (from the Arduino library manager)

Near the top of the sketch set the led pin. It is currently set to pin 7, assuming you are using an YJ-16013-NRF52832 or Jessinie module and a piece of veroboard.

Each door should be assigned a unique name. Set the LOCAL_NAME at the top of the sketch.

When programming the module, it is best to solder the power (3V3 and GND) and SWCLK and SDO cables directly to board and programmer. Jumper cables are convenient but become unreliable after repeated use.

If you are using the YJ-16013-NRF52832 module, the SWCLK (CK) and SDO (SWO) are pads on the board rather than edge connectors.

Multiple Door Bells

To have a front and back door bell, build a second BLE doorbell push button and set the LOCAL_NAME to “Back_Door” and the second name to the expectedDevices in the DoorBell_ESP32C_Monitor_Server.ino sketch below.

There are two options here:-

If you are a beginner, then the safe approach is to just mount the Dfrobot Beetle ESP32-C3 and MP3 speaker on a piece of veroboard in a small plastic box and power it via a USB supply and cable so that you are only exposed to 5V voltages.

If you are an experienced constructor who understands the dangers of working with Mains Power, you can build the receiver into the existing case using a power board from a USB supply.

A Safe Low Voltage Monitor for Beginners

The low voltage monitor consists of just an Dfrobot Beetle ESP32-C3 and an MP3 speaker (shown here) or buzzer, powered by a USB supply. The MP3 speaker pins pass through holes in the plastic case and a small piece of veroboard is soldered to the MP3 speaker pins to secure the speaker in place.

Again the circuit is trivial (pdf version)

If using a buzzer instead of the mp3 voice module, then connect the buzzer between pin 6 and GND. The Dfrobot Beetle ESP32-C3 has a built-in led on pin10 which is used as the indicator.

Retrofitting an existing doorbell receive involves mains power wiring and so should only be attempted by experienced constructors aware of the fatal dangers of main power.

The speaker and main pcb of the existing receiver are removed. The led board is kept and an 820R resistor added in series with the led so it can be driven by Pin 4 of the Dfrobot Beetle ESP32-C3.

To power the receiver, the power board from a USB supply was used an its mains power leads wired to the power pins of the in the receiver case.

A piece of veroboard is used to mount MP3 speaker and USB supply board and the Dfrobot Beetle ESP32-C3 board in the original case. The modified led board is used as the indicator led.

Before wiring up the MP3 speaker, load it with the tune .mp3 file you want played when it the door bell is pressed. As delivered the Voice Prompt Module has two files. Plug in the USB cable (supplied with the speaker) as shown here. NOTE Carefully: the red lead goes to the 5V pin and the silver side of the plug faces the 5V... GND labels.

The MP3 speaker will appear as a disk drive on your computer. Delete the two .mp3 files and copy your tune as 001.mp3. An example prompt file is here(See the next section for how to make your own.)

To test the tune touch the P1 pin to the GND lead.

Once you have loaded your tune and tested it, you can wire it into the board. Be very careful when wiring up the Voice Prompt module to correctly connect the 5V and GND pins.

Choose Your Own Tune

Install Audacity from https://www.audacityteam.org/download/ No extra libraries or add-ons are needed for this project.

To make your own tune, choose an alarm tone from one of the many freely available on the internet. Search for “free alarm tones”. Avoid those with low frequency components as the Voice Prompt Module does not render low frequencies.

Load the alarm into Audacity and then export it as a MONO file. Reload it and cut it to the desired length, adjust its volume and save it again for loading on the MP3 speaker

Install the ESP32 board support V3.0.7 (other versions may not work)

See https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html for instruction. Choose V3.0.7 from the drop down version.

Select the board Dfrobot Beetle ESP32-C3 as the board to program.

Plug in the board, if you don't see the COM port in your Arduino IDE you need to install the ESP32 CP201x USB to UART bridge VCP drivers

Set the USB CDC On Boot: “Enabled” and the Partition Scheme: “Huge APP (3MB No OTA/1MB SPIFFS)”

Unzip DoorBell_ESP32C3_Monitor_Server.zip to your Arduino sketch directory and install the SafeString and ESPAutoWiFiConfig libraries (available from Arduino library manager)

The

at the top of the sketch needs to match the LOCAL_NAMEs you set in the lp_BLE_DoorBell.inosketches for your door bells. Here a front and back door are monitored. Just delete the “Back_Door”, entry if you only have a front door bell.

Choose the appropriate pin to drive the indicator led. Pin 4 for the retrofit OR Pin 10 for the built-in led if making the low voltage version.

The DoorBell_ESP32C_Monitor_Server sketch provided has DEBUG enabled to print out debug messages. Comment out the #define DEBUG when you are finished check the operation.

To setup the monitor/reciever plug it in and after 30sec the led will start flashing rapidly indicating it could not connect to the WiFi network and has set up its own Access Point for you to connect to in order to configure the IP address and network SSID and password. See ESPAutoWiFiConfig for all the details. You can use an IP scanner program like Angry IP Scanner to see what IPs are already in use on your network. Choose a free one in the range x.x.x.200 to x.x.x.253 as these higher numbers are less likely to be pre-assigned.

Once the IP address and network access have been configured the monitor will reboot after a 30secs. Press the door bell button and check the tune / buzzer sounds. Move the monitor closer if is not detected.

Open the monitor's webpage http://10.1.1.106 for example if you set 10.1.1.106 as the monitor's IP and you will see a list of the door bells being scanned for and when they were last seen.

The DoorBell_ESP32C_Monitor_Server sketch scans for the expected BLE devices. When one is seen the time is recorded and the tune or buzzer is sounded and the led is set to flash slowly. When you return after being out, if the led is flashing slowly you know the door bell was pressed while you were away. You can then open the monitor's webpage to see which button was pressed and how long ago. Opening the monitor's web page also turns off the flashing led.

When a door bell is pressed the monitor's led starts flashing slowly. When you open the web page it cancels the flashing, so close the webpage after checking.

The DoorBell_ESP32C_Monitor_Server also provides a telnet server that up to 4 extension clients can connect to the provide remote door bell alerts.

No WiFi Option

If you don't want to connect the door bell to your WiFi network just comment out the #define ENABLE_WIFI at the top of the DoorBell_ESP32C_Monitor_Server.ino sketch.

The BLE DoorBell has a range of about 30m un-obstructed and so should work in most homes. However for longer range monitoring you can use an extension monitor which connect via telnet to the main monitor/receiver. This lets you add up to four (4) monitors in remote locations, like the back shed.

Construction

The construction is exactly the same as the for the Safe Low Voltage Monitor above.

Programming

As for the main monitor

Install the ESP32 board support V3.0.7 (other versions may not work)

See https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html for instruction. Choose V3.0.7 from the drop down version.

Select the board Dfrobot Beetle ESP32-C3 as the board to program.

Plug in the board, if you don't see the COM port in your Arduino IDE you need to install the ESP32 CP201x USB to UART bridge VCP drivers

Set the USB CDC On Boot: “Enabled” and the Partition Scheme: “Huge APP (3MB No OTA/1MB SPIFFS)”

Install the SafeString and ESPAutoWiFiConfig libraries (available from Arduino library manager)

open the DoorBell_ESP32C3_Extension.ino sketch and edit the line to set the IP to match one your monitor/receiver has been install on. For example

Then program the Dfrobot Beetle ESP32-C3 with the modified sketch.

Installation and Operation

Install the Extension Monitor using ESPAutoWiFiConfig to set its IP and network SSID and password. The extension will make a telnet connection to the main monitor and when the door bell is pressed the main monitor will send a message to the extension to play the tune / sound the buzzer and set the led to slowly flash. When you open the web page of the main monitor, e.g. http://10.1.1.106 (not the extension), the led flashing will stop.

The MP3 speaker can play more than just one tune. The tune to be played can be select via the MP3's serial connection (9600 baud). See section 4 Serialport command explanation of the instruction manual (local copy here)

ESP32–Tx connects to MP3 speaker-Rx and ESP32-Rx connects to MP3 speaker-Tx.

For Track 1 (001.mp3) use

const uint8_t track1[] = { 7E, 03, 00, 02, 00, 01, EF};

For Track 2 (002.mp3) use

const uint8_t track2[] = { 7E, 03, 00, 02, 00, 02, EF};

and send the track to the serial connection. E.g. for track 1 use

Serial.write(track1, 7);

Conclusion

This BLE Doorbell uses only a couple of components and is simple to construct by beginners and is immune to the RF interference from 'standard' doorbells. Experienced constructors can retrofitted an existing RF doorbell. It uses a very low power BLE module in the press button to notify the monitor when the button is pressed. You can monitor multiple push buttons and can choose your own tune/announcement to be played by the MP3 speaker. The monitor remembers when the button was pressed and a flashing led alerts you when you return home. A web page shows which button was pressed and how long ago.

A simple extension monitor was also presented when connects over WiFi to the main monitor to provide remote alerts and flashing indications.