IoT MQTT Based Heart Rate Monitor using ESP8266 & Arduino
In this project, we will use NodeMCU ESP8266, Arduino, and an Easy Pulse Sensor to make an IoT-based heart rate monitor. We will show the Pulse Rate or BPM value on both the OLED Display…
Know the mission before touching a wire.
Understand what you are making, prepare the right tools, and make the workbench safe.
Project details
IoT MQTT Based Heart Rate Monitor using ESP8266 & Arduino is a iot project. In this project, we will use NodeMCU ESP8266, Arduino, and an Easy Pulse Sensor to make an IoT-based heart rate monitor. We will show the Pulse Rate or BPM value on both the OLED Display…
- Source pages
- 1153-1159
- Named parts
- 8
- Build goal
- Working, tested prototype
Tools you need
- Digital multimeter
- Wire stripper and side cutters
- Soldering iron with a fine tip
- Current-limited bench supply
- Computer with a data-capable USB cable
Use eye protection, good lighting, and a clean insulated surface throughout the build.
Safety precautions
- Disconnect every power source before changing a connection.
- Check component polarity, pinout, and supply voltage twice.
- Use a current limit for the first power-up.
- Keep liquids, loose metal, and uninsulated wires away from the bench.
Gather, identify, and understand every part.
Use the standardized inventory, then open What's this? to learn each part's role, advantages, limitations, handling, and specifications.
What's this?Image, role, pros, cons, handling & specifications
MODULE LEARNING VIEWArduino Board or Arduino Nano
A programmable controller that reads inputs, makes decisions, and drives the project's outputs.
What it does hereIt is the control centre and must use the documented board, pin map, supply, and logic level.
Buy / compare this part ↗Advantages
- Reprogrammable and reusable
- Large learning ecosystem
- Complex behaviour remains changeable
Limitations
- GPIO voltage and current are limited
- Some pins affect boot or communication
- Loads normally need a driver
Handling
- Disconnect power before rewiring
- Avoid static discharge
- Never power motors, relays, or pumps directly from GPIO
Specifications to verify
- Use the exact model, value, package, and rating listed for Arduino Board or Arduino Nano; similar-looking parts are not always interchangeable.
- Confirm operating voltage, logic level, pinout, memory, USB interface, and maximum GPIO current.
What's this?Image, role, pros, cons, handling & specifications
MODULE LEARNING VIEWNodeMCU Board ESP8266
A programmable controller that reads inputs, makes decisions, and drives the project's outputs.
What it does hereIt is the control centre and must use the documented board, pin map, supply, and logic level.
Buy / compare this part ↗Advantages
- Reprogrammable and reusable
- Large learning ecosystem
- Complex behaviour remains changeable
Limitations
- GPIO voltage and current are limited
- Some pins affect boot or communication
- Loads normally need a driver
Handling
- Disconnect power before rewiring
- Avoid static discharge
- Never power motors, relays, or pumps directly from GPIO
Specifications to verify
- Use the exact model, value, package, and rating listed for NodeMCU Board ESP8266; similar-looking parts are not always interchangeable.
- Confirm operating voltage, logic level, pinout, memory, USB interface, and maximum GPIO current.
What's this?Image, role, pros, cons, handling & specifications
Easy Pulse Sensor, HRM-2511-E Pulse Sensor
A sensor converts a physical condition into an electrical signal the circuit can measure.
What it does hereIt provides project input as an analogue, digital, resistive, frequency, or calibrated signal.
Buy / compare this part ↗Advantages
- Adds real-world awareness
- Can usually be tested independently
- Often supports calibration
Limitations
- Readings can drift
- Placement affects results
- Some sensors need warm-up or calibration
Handling
- Protect the sensing surface
- Observe supply voltage and polarity
- Keep signal leads away from noisy power wiring
Specifications to verify
- Use the exact model, value, package, and rating listed for Easy Pulse Sensor, HRM-2511-E Pulse Sensor; similar-looking parts are not always interchangeable.
- Confirm supply range, output type, measurement range, accuracy, response time, and pin order.
What's this?Image, role, pros, cons, handling & specifications
OLED Display, 0.96" I2C OLED Display
An output component turns an electrical control signal into light, sound, motion, switching, or displayed information.
What it does hereIt presents the circuit result or acts on the physical world.
Buy / compare this part ↗Advantages
- Makes system state visible
- Can be tested separately
- Supports clear troubleshooting
Limitations
- Loads may exceed controller current
- Polarity or driver direction can matter
- Inductive loads create voltage spikes
Handling
- Use the documented driver stage
- Check polarity and load current
- Add flyback protection for inductive loads
Specifications to verify
- Use the exact model, value, package, and rating listed for OLED Display, 0.96" I2C OLED Display; similar-looking parts are not always interchangeable.
- Confirm voltage, current, polarity, interface, driver requirements, and duty cycle.
What's this?Image, role, pros, cons, handling & specifications
Power Supply, 5V Supply
A power component supplies, converts, stores, or regulates energy for the project.
What it does hereIt must provide the documented voltage, polarity, isolation, and sufficient current safely.
Buy / compare this part ↗Advantages
- Stable power improves reliability
- Current limiting protects first tests
- Regulation reduces resets and noise
Limitations
- Wrong polarity can cause immediate damage
- Underrated parts overheat
- Mains circuits require qualified supervision
Handling
- Measure output before connection
- Use a fuse or current limit
- Insulate exposed conductors
Specifications to verify
- Use the exact model, value, package, and rating listed for Power Supply, 5V Supply; similar-looking parts are not always interchangeable.
- Confirm input/output voltage, current, polarity, connector, isolation, and thermal rating.
What's this?Image, role, pros, cons, handling & specifications
Checking the Pulse Rate (BPM) on the OLED and Cloud
An output component turns an electrical control signal into light, sound, motion, switching, or displayed information.
What it does hereIt presents the circuit result or acts on the physical world.
Buy / compare this part ↗Advantages
- Makes system state visible
- Can be tested separately
- Supports clear troubleshooting
Limitations
- Loads may exceed controller current
- Polarity or driver direction can matter
- Inductive loads create voltage spikes
Handling
- Use the documented driver stage
- Check polarity and load current
- Add flyback protection for inductive loads
Specifications to verify
- Use the exact model, value, package, and rating listed for Checking the Pulse Rate (BPM) on the OLED and Cloud; similar-looking parts are not always interchangeable.
- Confirm voltage, current, polarity, interface, driver requirements, and duty cycle.
What's this?Image, role, pros, cons, handling & specifications
Open the Arduino Code Part Serial Monitor. Then, on Serial
A programmable controller that reads inputs, makes decisions, and drives the project's outputs.
What it does hereIt is the control centre and must use the documented board, pin map, supply, and logic level.
Buy / compare this part ↗Advantages
- Reprogrammable and reusable
- Large learning ecosystem
- Complex behaviour remains changeable
Limitations
- GPIO voltage and current are limited
- Some pins affect boot or communication
- Loads normally need a driver
Handling
- Disconnect power before rewiring
- Avoid static discharge
- Never power motors, relays, or pumps directly from GPIO
Specifications to verify
- Use the exact model, value, package, and rating listed for Open the Arduino Code Part Serial Monitor. Then, on Serial; similar-looking parts are not always interchangeable.
- Confirm operating voltage, logic level, pinout, memory, USB interface, and maximum GPIO current.
What's this?Image, role, pros, cons, handling & specifications
MODULE LEARNING VIEWOpen the Serial Monitor tab for NodeMCU ESP8266 Output as
A programmable controller that reads inputs, makes decisions, and drives the project's outputs.
What it does hereIt is the control centre and must use the documented board, pin map, supply, and logic level.
Buy / compare this part ↗Advantages
- Reprogrammable and reusable
- Large learning ecosystem
- Complex behaviour remains changeable
Limitations
- GPIO voltage and current are limited
- Some pins affect boot or communication
- Loads normally need a driver
Handling
- Disconnect power before rewiring
- Avoid static discharge
- Never power motors, relays, or pumps directly from GPIO
Specifications to verify
- Use the exact model, value, package, and rating listed for Open the Serial Monitor tab for NodeMCU ESP8266 Output as; similar-looking parts are not always interchangeable.
- Confirm operating voltage, logic level, pinout, memory, USB interface, and maximum GPIO current.
Connect one verified path at a time.
Explore the named components and standardized signal flow, then use Source Check to verify exact physical pins, values, and topology before applying power.
Trace this circuit.
IoT MQTT Based Heart Rate Monitor using ESP8266 & Arduino: interactive parts, standardized terminals, responsive anchored wires, student explanations, and the original circuit reference in one shared system.
Trace before wiring
Follow power, ground, inputs, processing, and outputs in that order. Never guess a pin from package shape alone.
Connect with power off
Make short, labelled connections and share a common ground only where the schematic requires it.
Inspect every joint
Check continuity, polarity, adjacent shorts, and loose connections before the first power-up.
Open all source diagrams and build views 5 visuals
Confirm the hardware-only control path.
This project does not include firmware in the source. The circuit itself provides the required behaviour.
How to connect
- Match every controller label to the circuit view and source pin map.
- Join grounds before signal wires when separate low-voltage supplies are used.
- Keep motors, relays, pumps, and other loads on a suitable driver and external supply.
Common mistakes
Reversed VCC/GND, board-label versus GPIO-number confusion, missing common ground, and charge-only USB cables.
Troubleshoot
Disconnect loads, continuity-test one path at a time, then test with a current limit.
Software preparation
No IDE, board package, library, or firmware upload is required for this project.
If you add a programmable controller as an extension, document its pin map separately.
How to upload code
The original design is implemented entirely in hardware, so proceed after verifying the circuit and supply.
Assemble, deploy, test, and troubleshoot.
Use the complete source notes in build order, then pass the final checks before calling the project finished.
Build in functional stages
- Power and regulation
- Controller or processing stage
- Inputs and sensors
- Outputs and loads
- Enclosure and strain relief
Power up safely
- Inspect unpowered continuity first
- Apply the lowest safe current limit
- Measure supply rails before signals
- Add one load at a time
- Record expected and actual results
Work from simple to complex
- Confirm power, ground, polarity, and orientation
- Compare each pin with the source
- Test inputs separately from outputs
- Replace only one variable at a time
- Power off before every correction
Follow the documented instructions.
These notes come from this project's source and remain in their original order.
Project overview
Project build noteIn this project, we will use NodeMCU ESP8266, Arduino, and an Easy Pulse Sensor to make an IoT-based heart rate monitor. We will show the Pulse Rate or BPM value on both the OLED Display and the MQTT Dashboard. In one of our previous projects, we used an Optical Pulse Sensor with NodeMCU ESP8266 that could connect to a WiFi network and regularly send the Heart Rate (BPM) value to the Thingspeak Server.
With the free version of Thingspeak Server, you can only do certain things. The data doesn't get sent to Thingspeak Server until 15 seconds have passed. Because of this, we need to choose a method that can easily meet our needs. MQTT protocol fulfills our requirements. MQTT is a lightweight messaging protocol for networks with low bandwidth, high latency, and low reliability. Because of its features, MQTT is a great way to send a lot of sensor messages to platforms for analytics and cloud solutions. So, Ubidots is a good MQTT platform for IoT projects. With the Ubidots platform, we can send data to the cloud from any device that can connect to the Internet. In this IoT MQTT Based Heart Rate Monitor Project, the Easy Pulse Sensor will be connected to Arduino and ESP8266. First, we will show the Pulse Rate Data on the OLED Display. The data will then be sent to the Ubidtos MQTT Cloud through the WiFi connection.
Easy Pulse Sensor
The Easy Pulse Sensor is a pulse sensor that you can make yourself. It is made for hobbyists and educational uses. It is used to explain how photoplethysmography works (PPG). PPG is a non-invasive way to find the pulse wave of the heart and blood vessels from a fingertip. A transmission mode PPG probe (HRM-2511E) is used in the Easy Pulse Sensor. On one side of the Sensor, the finger is lit up by an infrared light source. On the other side of the sensor is a photodetector that measures small changes
in the intensity of the light that gets through. These changes are caused by changes in the amount of blood in the tissue. The onboard components and instruments give an analog PPG waveform that is clean and filtered. The digital pulse output is also shown by the LED on the board. Both the analog and the digital signals match the heartbeat. Block Diagram: IoT Based Heart Rate Monitor using ESP8266 Arduino on MQTT Let's look at the block diagram to make things clear and easy to understand. This is a simple diagram that shows how the project will work: ESP8266, Arduino, and a pulse sensor are used to make an IoT-based heart rate monitor. First, we hook up the Pulse Sensor to the Arduino. We send the data from Arduino to NodeMCU ESP8266 through UART Communication. We could have put the Pulse Sensor directly on the NodeMCU ESP8266 Board. But the pulse sensor doesn't seem to be working and the Serial Monitor doesn't show anything. So it's easy to get the data from Arduino to ESP8266 by using the UART method.
The NodeMCU ESP8266 can connect to the WiFi Network. The BPM topic is then uploaded or published to MQTT Cloud Called Ubidots. As a subscriber, you can use the Ubidots Dashboard to look at the published data on your computer or phone. This is how the IoT Based Heart Rate Monitor Project works in its entirety.
Part Required
Project build noteArduino Board or Arduino Nano NodeMCU Board ESP8266 Easy Pulse Sensor, HRM-2511-E Pulse Sensor OLED Display, 0.96" I2C OLED Display Power Supply, 5V Supply Connecting Wires Breadboard Circuit Diagram & Connections You can turn the block diagram shown above into a circuit diagram. I make the schematics with Fritzing. Pulse Sensor ESP8266 and Arduino are easy to connect to each other. To talk between ESP8266 and Arduino, we use the Software Serial Method. Connect the TX and RX pins of the ESP8266 to the digital 7 and 8 pins of the Arduino. Connect the pulse sensor's input to the Arduino A0 Pin. In the same way, connect the Pulse Sensor's VCC and GND pins to Arduino's 5V and GND pins.
Since the OLED Display is an I2C Module, connect its I2C Pins (SDA and SCL) to D2 and D1 on the NodeMCU. Connect the OLED Display's VCC and GND pins to the 3.3V and GND pins on the ESP8266. Checking the Pulse Rate (BPM) on the OLED and Cloud Upload the code to the Arduino and NodeMCU Board. After you've uploaded the code, attach the Probe to your finger or ear if you're using the Earlobe clip. Open the Arduino Code Part Serial Monitor. Then, on Serial Monitor, you will see the Pulse Rate or BPM Value. Open the Serial Monitor tab for NodeMCU ESP8266 Output as well. You will be able to see data coming in through Arduino's UART. Serial Monitor will also show the log of the data that was published. The BPM value can also be seen on the OLED Display, in addition to the Serial Monitor. If you don't want this project to have a MQTT connection,
you can use an OLED to see the Heart Rate data instead.
You built IoT MQTT Based Heart Rate Monitor using ESP8266 & Arduino.
You followed the full workflow from understanding the mission to testing the finished project. That is a real engineering achievement - well done.
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