ESP32 Cellular Failover Gateway Kit: Zero-Downtime MQTT with Automatic GSM Fallback

Every part needed, pre-tested for compatibility, with an AI build companion trained on this exact project. Shipped from Bengaluru in 3-5 days.

Remote monitoring of temperature and humidity often depends on a stable WiFi connection — but WiFi is anything but predictable. With this kit, you construct a resilient gateway that publishes DHT22 sensor data over MQTT, and the instant WiFi drops, a SIM800L GSM module steps in. Data continues to flow over cellular GPRS without a single missed reading, making it ideal for agricultural cold storage, pharmaceutical logistics, or any field deployment where connectivity can’t be taken for granted.

What You'll Build

You’ll assemble and program a self-contained environmental monitor that reads two DHT22 sensors, displays live data on a 0.96-inch OLED, and transmits via MQTT. The ESP32 constantly pings the WiFi network; if no response, it toggles to the SIM800L’s GPRS, re-establishes the MQTT session, and continues publishing — all while logging the switch event locally. The final unit sits inside a vented enclosure, powered by a stable 5V 3A supply you’ve regulated yourself.

What You'll Learn

• Implementing robust MQTT client logic on ESP32 with keep-alive and last-will testament
• Interfacing a SIM800L GSM module, managing AT commands, and provisioning a GPRS PDP context
• Designing a noise-free power section with an LM2596 buck converter, bulk 1000µF decoupling, and 100nF high-frequency bypass capacitors
• Structuring failover code that monitors WiFi RSSI, triggers network switch, and updates an OLED status indicator in real time

Kit Contents

Why Buy This Kit Instead of Sourcing Parts Separately

Who This Kit Is For

B.Tech ECE and EEE students tackling final-year IoT or embedded systems projects will find the failover logic directly applicable to real-world industry requirements. Participants in Smart India Hackathon or similar competitions can adapt the gateway for sensor mesh networks. Advanced ATL Tinkering Lab mentors and researchers at IITs, NITs, VIT, or BITS building remote data loggers will appreciate the pre-integrated GSM component and comprehensive circuit design.

Built and Backed by Compoden

Every Compoden kit ships with an AI build companion trained on this exact project — accessible via a QR code on the box, with WhatsApp and email backup. We've spent 10 years building projects for makers, schools, and institutions across India. If a part fails because of a manufacturing defect, replace it free within 7 days.

Choose your assembly option:

• Soldering Kit — 25W soldering iron, 60/40 solder wire, flux, and small perfboard for permanent assembly.
• Breadboard Combo — 800-point full-size breadboard with 65-piece jumper wire pack for solderless prototyping.