Cellular IoT Monitor  

Transmit sensor data from remote locations (i.e., vacant home) without internet. Transfer data to email, text, Google Sheets, IFTTT, Home Assistant, and more for less than $2 per month.

How It Works

An inexpensive IoT SIM card gains access to the cloud via a cellular connection.

The HUB connects to the cellular network or wifi or both.

The HUB can operate as a stand-alone unit with its own sensors.

The HUB can also collect data wirelessly from separate sensor platforms.

The hub software - AmbientHUB - and the sensor software - AmbientAP - are written in C++ with the using the Arduino IDE.

The AmbientHUB software controls an ESP32 micro-controller connected with onboard sensors and an optional OLED display.

Hands on Technology presentation of 2/2/2022

Available
Summary:

Additional developments since the above description are reflected below and in the software.

Tested With

• Botletics SIM7000A cellular modem Arduino shield

• LiLLYGO SIM7000G board with integrated ESP32 Wrover

  

• and-global SIM7000A module

Supported Protocols

The AmbientHUB software can receive the AmbientAP sensor data using the listed protocols.

• http where each sensor is configured as a server which can be polled by the hub using a GET command.

• ESP-Now a lighter footprint protocol by which the sensors push the data to the hub based on its MAC address. https://www.espressif.com/en/products/software/esp-now/resources

Formatting Options

The AmbientHUB software collects the sensor values for hourly transmission via the Hologram IoT cellular platform to the listed website services.

Supported Services via Cellular

• https://io.adafruit.com/ MQTT for dashboard and redundant IFTTT webhook route

• https://ifttt.com/ for notifying to up to 20 email accounts plus Google sheets

• https://dweet.io/ which simply saves the messages in scratchpad format as a backup in case of IFTTT failure

Supported Services via Wifi

• Home Assistant or any MQTT Broker using a local wifi router

• Telegram for tailored commands

Threshold Alert

The AmbientHUB software provides
immediate alerts when sensors cross adaptive thresholds.

Builtin Modules

• An ESP32 or a D1 Mini 8266 micro-controller

• temperature / humidity sensors BME-280, MCP9808, DHTxx, AHT10, SHT20

• An optional SSD1306 OLED display https://www.amazon.com/gp/product/B07W1PT6VK

• door / window sensors

• illumination sensors

• flood sensors

• PIR/ motion Sensors

• HC-SR04 or HC-SR04P Ultrasonic sensor

• DC 5V 1 Channel Relay Module Board Shield High/Low Level Trigger with Optocoupler

Further Discussion

After trying several configurations, here is what I'd recommend:

• LillyGo over Botletics since it has the ESP32 on the board with the cellular modem.

• The ESPNOW protocol over client/server because of the lighter footprint and easier implementation.

• Use the adaFruit path to access IFTTT for more reliable performance.

• Standardize on the ESP32 vs 8266 for more robust capabilities and to simplify your life moving forward.

• Dweet has bitten the dust. Get on the google to find an alternative.

• Use a timer to disconnect the power from the LillyGo or Botletics daily.

All of the above alternatives can be configured in the software.

## Observations

• Kudos to Hologram. They have a polished dashboard which makes life easy to monitor.

• The software is very adaptable to other applications. See my GarageController, for example.

## Results

As of now (September 20, 2025) the system has:

• Detected a failed AC system by noting rising temperature and humidity.

• Helped identify a wall betwwen our condo and an attached storage shed that is uninsulated.

• Provided peace of mind as we can veerify temperature, humidity, doors, lights, basement dryness, etc.

Conclusions

• This system has worked fine and has paid for itself.

• We have eliminated the need for WiFi or homewatch services while absent.

## Attributions and References