📡 Overview
In this project, we build a long-range wireless temperature monitoring system using LoRa radio communication, a PIC microcontroller, and a NodeMCU ESP8266.
The system allows you to monitor temperature from remote locations such as a garden, shed, greenhouse, or outdoor enclosure — and view live data anywhere in the world using the ThingSpeak cloud platform.
Unlike typical WiFi-based sensors, this system does not require WiFi at the sensor location, making it significantly more secure and much higher range.
🧠 System Architecture
The project is split into two main parts:
[ Sensor Node (Outdoor) ]
PIC16F628 → DS18B20 Temperature Sensor → LoRa Transmitter
↓
Wireless Long-Range Link (LoRa)
↓
[ Base Station (Indoor) ]
LoRa Receiver → NodeMCU ESP8266 → ThingSpeak Cloud
🌍 How It Works
1. Sensor Node (Outdoor Unit)
The outdoor unit is built around a PIC16F628 microcontroller connected to a DS18B20 temperature sensor.
The PIC reads temperature data and formats it into a simple packet structure:
T24E
Where:
- T = start of packet
- 24 = temperature value (°C)
- E = end of packet
This data is transmitted via LoRa at a fixed interval (e.g. every 5 minutes).
To conserve power, the microcontroller spends most of its time in a low-power state between transmissions.
2. Receiver Node (Indoor Unit)
The base station uses a NodeMCU ESP8266 connected to a LoRa receiver module.
It:
- Receives incoming LoRa packets
- Extracts the temperature value between T and E
- Validates and processes the data
Once decoded, the value is passed to the WiFi stage.
3. Cloud Upload (ThingSpeak IoT)
The NodeMCU uploads the processed temperature value to ThingSpeak, allowing:
- Real-time graphs
- Historical data logging
- Remote access from any device with internet
No custom app is required — just open your ThingSpeak channel in a browser.
📊 ThingSpeak Dashboard
ThingSpeak provides:
- Live updating temperature graph
- Automatic data logging
- Mobile and desktop access
- Long-term data storage (ideal for monitoring trends)
Once configured, the system continuously logs sensor data at your chosen interval.
⚡ Power & Efficiency Design
To make the system suitable for outdoor battery operation:
- PIC microcontroller sleeps between transmissions
- LoRa module remains inactive when not sending data
- System wakes periodically to transmit readings
This approach significantly reduces power consumption and allows long-term battery operation.
🧩 Key Features
- Long-range wireless communication using LoRa
- No WiFi required at the sensor node
- Secure remote sensing (no exposed credentials outdoors)
- Cloud-based monitoring via ThingSpeak
- Low-power design for battery operation
- Simple and reliable packet protocol (TxxE)
- Easily expandable to multiple sensor types
🔧 Possible Upgrades
This system can be expanded to include:
- Humidity monitoring
- Soil moisture sensing
- Battery voltage tracking
- Multi-node sensor networks
- Alerts via ThingSpeak webhooks or email
💡 Why This System Is Useful
Most off-the-shelf IoT sensors rely entirely on WiFi, which limits range to a typical home network and requires storing credentials on the device.
This design solves that problem:
- The sensor node does not store WiFi credentials
- Communication range is significantly extended using LoRa
- The system can operate in remote outdoor environments
- Data is still accessible globally via the cloud
🏗️ Hardware Overview
Sensor Node:
- DS18B20 temperature sensor
- PIC16F628 microcontroller
- LoRa transmitter module
Base Station:
- LoRa receiver module
- NodeMCU ESP8266 (ESP-12E)
- WiFi connection to ThingSpeak
🔗 Build Process
You can assemble this project using a breadboard or prototype setup by following the schematics.
PCB design files will be added in a future update.
⚙️ Setup Summary
- Create a ThingSpeak account
- Create a new channel and enable Field 1 (Temperature)
- Copy your Channel ID and API Key
- Flash the PIC with the provided HEX firmware
- Upload the NodeMCU Arduino sketch (insert WiFi + API credentials)
- Power both units and begin logging data
📦 What’s Included in the Download
This project pack includes:
- PIC assembly source code (for reference)
- Pre-compiled PIC HEX firmware (ready to flash)
- NodeMCU Arduino IDE sketch
- Full wiring diagrams (both nodes)
- ThingSpeak setup guide
- Packet format documentation (TxxE)
- Step-by-step build instructions
🚀 Real-World Applications
A temperature data logger like this is widely used in:
- Cold chain logistics
- Pharmaceutical storage monitoring
- Food safety (HACCP compliance)
- Laboratory temperature mapping
- HVAC system optimisation
- Agricultural and greenhouse monitoring
📌 Final Notes
This project demonstrates how low-cost embedded systems can be combined to create a long-range IoT monitoring solution without relying on WiFi at the sensor location.
By combining:
- PIC microcontroller processing
- LoRa long-range communication
- ESP8266 cloud connectivity
…you get a flexible, scalable remote monitoring system that can be deployed almost anywhere.
Download the full project here
What is a temperature logger?
A temperature data logger is a portable device used to automatically measure and record environmental temperatures over a specific period. It ensures that sensitive goods remain within safe limits by providing a reliable, automated alternative to manual thermometer checks.
They are essential tools across various industries, fulfilling the following primary uses:
- Cold Chain Shipment Monitoring: Tracking perishable goods (e.g., produce, dairy) and pharmaceuticals in transit to guarantee that conditions remain within safe parameters.
- Pharmaceutical and Vaccine Storage: Ensuring drugs, blood samples, and vaccines are kept at required temperatures (e.g., +2°C to +8°C) to prevent spoilage and maintain their efficacy.
- Food Safety and HACCP Compliance: Monitoring refrigerators, freezers, and processing facilities to ensure strict food safety regulations are continuously met.
- Laboratory and Equipment Mapping: Performing temperature mapping in scientific environments, incubators, or industrial ovens to identify hot and cold spots.
- Building Management & HVAC: Optimizing climate control systems in commercial and agricultural buildings for efficiency and product quality.