[This is the description page of current state of EXPLOG project. This will be updated occasionally. So please keep an eye on the logs to know what happens when.]

EXPLOG stands for "Exploration Logger". It is an opensource device that can log a variety of navigation, weather and kinematic parameters very precisely. It is a modular, multi-purpose and multi-sensor device that is available in many form factors. It's nothing groundbreaking or cutting edge, but simply a device that integrates widely available embedded sensors in a single portable form factor. This is helpful when you're exploring new places and go hiking. You may already have GPS on your phone, or an altimeter on your watch. But why can't we have a single, device that can fulfill every data logging requirement we need ? You could be exploring a forest, some mountains or a tribal village for your thesis. Or you'd using a drone or a wheeled robot to explore a place that you normally can't access such as a disaster struck place. In any such situations, having a device that can show you everything from temperature, pressure, your current altitude to your GPS location could become really handy. EXPLOG tries to accomplish that. There are three form-factors EXLPOG will be available,

  1. EXPLOG Standard - A handheld version with high capacity 18650 Li-Ion cells and TFT/monochrome LCD.
  2. EXPLOG Mini -  Smaller version which is a self-powered, detachable module that can be attached to your robot or drone.
  3. EXPLOG Black Box - A compact module without a display but all the rest of the features.


Application Areas

  1. Scientific Research - this all-in-one embedded sensor package lets you collect climate information with accurate time and geographical location.
  2. Sports and Fitness- lets you collect sports performance data for real-time and post analysis. EXPLOG will be a persistent companion throughout your expedition, recording everything on your path without troubling you.
  3. Robotics - being modular and power redundant makes EXPLOG a suitable addition for remotely operated robots and drones. It is easier and convenient to use a standalone sensor module than to integrate everything onto the robot itself. Data from EXPLOG can be shared to the robot controller in real-time.
  4. Security and Surveillance - when you open the door to your room, a sudden pressure change happens. Together with noise level and proximity measurement, you can detect intrusions at homes or offices. EXPLOG can notify you in such events over internet connected through WiFi.
  5. Weather Forecasting - sudden variations in pressure and humidity could be an indication of an imminent storm. EXPLOG can monitor these and warn you, which makes it your personal weather station.
  6. Agriculture - lets you monitor and log climate conditions of your greenhouse or farm. EXPLOG can be programmed to notify you in case of any abnormalities. 

Advanced Applications

Open Data Pool

Open Data Pool is a public cloud system concept where users from all around the world can share data collected from EXPLOG devices. Data can be shared in real-time as per user's choice and also in CSV or similar formats. Real-time sharing will require active internet connection. The shared data can be either privately kept or shared to the public. Users will be able to access and download public data in real-time. For example, you could know the exact weather conditions of place at the other side of the globe if an EXPLOG device is active in that place. The possibilities are unlimited. As this is matter of data sharing such as one's location, there'll be privacy concerns and other complications. But the user will be always in control of what is being shared as this is an open source project, which gives you full access to the firmware source code and hardware designs.

For this to work, every EXPLOG device will need a unique ID, someone has to design the cloud system, and maintain it. That's why it's in the advanced spectrum of applications, a doable one of course.


EXPLOG Standard - Dimensions

Exploded View

EXPLOG Standard exploded view

3D Design

The best way to envision what we really want to make is to do a 3D design. You can then better decide component placements, sizes, volume and all such physical parameters beforehand. That'll save time. The 3D model for EXPLOG was designed in Autodesk Fusion 360 and will be available for downloading once it's ready for printing. The PCBs are just for illustrative purpose only.

Fully packed
There's still space left under the main PCB for other modules and antenna
3D printable and modular design with all bolt joints. Wall thickness is from 4 - 5 mm
LoRa transceiver is at the other side of main PCB
Display with fastened with two screws.
Still not sure how to make the buttons - probably 3D print it or make with silicone.

How does it work ?

The brain of the EXPLOG will be an ESP32 (ESP-WROOM32) module. ESP32 is a system-on-a-chip with dual core 32 bit Tensilica processor running at 240 MHz, WiFi, Bluetooth, BLE and more, produced by Espressif Systems. The ESP-WROOM32 is a module with integrated antenna, flash memory and other necessary circuits. It is a really powerful and feature rich chip in a single package and costs less than similarly featured chips. ESP32 is the big brother of the popular ESP8266. Here's the basic block diagram of proposed EXPLOG system design.

Air quality, temperature, pressure, accelerometer, light intensity, proximity, RTC, humidity, magnetometer and gyro sensors are interfaced to the WROOM32 module via a single I2C line which greatly reduces the number of I/O pins required. The microphone amplifier output is sampled by an ADC which is also connected to the I2C line. The GPS module is connected to one of the UART ports of ESP32 and the microSD card to one of SPI ports. The LoRa module based on SX1276/SX1277/ SX1278/SX1279 will be connected to the HSPI hardware SPI port of the ESP32. The display we plan to use will be a 1.8" TFT display or any other monochrome LCD display of similar size.

The keypad is a 7 key matrix and is interfaced through an I2C keypad controller TCA8418. For the LCD, 3 GPIOs will be used drive the 3 wire SPI interface. The power supply section will consist of two 18650 Li-Ion cells each with 3000 mAh capacity for the Standard model, and a single Li-Ion prismatic cell for the Mini and Black Box versions. The 18650 cells will be paralleled to produce 3.7V with a total capacity of 6000 mAh. Prismatic cells will have capacities depending on their selection. A dedicated Li-Ion charge controller will allow you to charge the cells via a USB cable. The 3.6 to 4.2 V from the cells will be converted to 3.3V using a DC-DC converter on board. ESP32, the sensors and the display will run at 3.3V.

The USB cable also allows you to read real-time data from EXPLOG or the microSD card using an interfacing software designed in Processing language. Additionally, you can fetch the data via WiFi, Bluetooth or LoRa depending on the configurations you set.


EXPLOG's firmware source code is released under MIT License and all hardware design files under Creative Commons 4.0 Attribution-ShareAlike. Please read more about,


Image sources :

  1. https://unsplash.com/photos/PjNRxr0WpeQ
  2. https://unsplash.com/photos/FvJuUaXWGiQ
  3. https://unsplash.com/photos/L97Hsnt-mAI
  4. https://unsplash.com/photos/pa0rr3rVB-U
  5. https://unsplash.com/photos/zTUZACXVPkE
  6. https://unsplash.com/photos/OYFHT4X5isg
  7. https://unsplash.com/photos/b0CEpd0m1QY
  8. https://commons.wikimedia.org/wiki/File:K10_black_rover_at_Haughton_Crater.jpg