EXPLOG : Exploration Logger

A handheld device that can monitor and log navigation and weather parameters in realtime and share data over WiFi, BT, LoRa & USB

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EXPLOG is a modular and portable logging device that packs many embedded sensors. It can monitor and log various navigation and weather parameters such as accurate GPS location, direction, speed, acceleration, orientation, temperature, pressure, altitude, humidity, air quality, noise level, light intensity, and proximity simultaneously. The saved data can be exported to a computer or phone via USB, WiFi or BT and also an on-board LoRa transceiver allows for data sharing between devices and remote data acquisition. It can be used for research, fitness and sports performance analysis, and can function as a portable weather station and a surveillance device.

The name is a wordplay on "exploration" and "logger".

This project is under prototyping stage. I'm using ESP32 as the main controller. All the sensors are in the form of breakout modules for now. Once I complete the prototyping, I wish to make a custom PCB and a 3D printed case.

[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 might be a new term for you becasue Google search returned only 29 results for it. EXPLOG is not related to oil exploration or anything but the mere human curiosity and the urge to explore the unknown.

EXPLOG is an opensource device that can log a variety of navigation and weather parameters very precisely - it is a complete, modular and standalone sensor package. 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 addresses that need. 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 - An even smaller module without a display but all the rest of the features.


  • High sensitivity unassisted GPS.
  • Geo-location alarm.
  • Ambient temperature measurement.
  • Pressure and altitude measurements.
  • Humidity measurement.
  • Air quality measurement (particulates and other gases)
  • Ambient noise level measurement.
  • Light intensity measurement (Visible, IR and UV)
  • IR Proximity measurement.
  • Compass/Magnetometer for navigation.
  • Orientation and acceleration sensing with Gyro and Accelerometer.
  • microSD card support.
  • WiFi and Bluetooth connectivity with ESP32.
  • Remote data sharing and acquisition through LoRa transceiver module.
  • Li-Ion cells (3.3V operation and 6000 mAh capacity for standard version)
  • TFT/Monochrome LCD.
  • USB connectivity.
  • External I2C and SPI interfaces.

Application Areas

  1. Scientific Research - this all-in-one sensor package lets you collect climate information with accurate time and geographical location.
  2. Sports and Tourism - 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. 

How does it work ?

The brain of the EXPLOG will be an ESP32 (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 WROOM32 is module with integrated...

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  • Choosing the Right Sensors

    Vishnu M Aiea03/19/2018 at 11:21 3 comments

    EXPLOG needs a lot of sensors obviously and there's a large list to choose from. Some of the criteria for selection of sensors are,

    • Size - must be small with less than 5 mm height, and be surface mountable and reflow solderable  or through-hole solderable.
    • Interface - I2C compatible.
    • Operating voltage - 3.3V
    • Calibration - should be either factory calibrated or user calibratable.
    • Global availability
    • Cost

    We need to make the right choices by considering the global availability and cost of each sensor to make sure that others will be able to get them to replicate/modify the device. These are what I've been able to come up with. Datasheets of all these sensors will be available at the file section of this project.

    Barometric Pressure Sensor

    1. DPS310 from Infineon
    2. BMP280 from Bosch
    3. BMP380 from Bosch
    4. BMP388 from Bosch
    5. BME680 from Bosch
    6. MPL3115A2 from Maxim

    We need a sensor to accurately measure barometric air pressure becasue we need accurate pressure measurements for calculating the altitude accurately. DPS310 was my first choice becasue I had received an evaluation module from Infineon as part of a give away. But not everybody is going to get these as they are not available in the usual maker markets. BMP280 on the other hand is widely available and most are familiar with. But they're not the best ones our there. Let's have a comparison of features of sensors from leading manufacturers.

    Operation range300 - 1200 hPa300 - 1100 hPa300 - 1250 hPa300 - 1250 hPa300 - 1100 hPa200 - 1100 hPa
    Abs. Max. Pressure10000 hPa20000 hPa20000 hPa20000 hPa20000 hPa5000 hPa
    Max. Resolution (Pressure)24-bit20-bit24-bit24-bit20-bit20-bit
    Precision0.005 hPa0.0016 hPa0.003 hPa0.0016 hPa0.0018 hPa0.0025 hPa
    Absolute Accuracy ± 1 hPa± 1 hPa ± 0.5 hPa± 0.5 hPa± 0.6 hPa± 4 hPa
    Relative Accuracy± 0.06 hPa± 0.12 hPa± 0.06 hPa± 0.08 hPa± 0.12 hPa± 0.5 hPa
    Temperature Coefficient Offset0.5 Pa/K1.5 Pa/K1.2 Pa/K± 0.75 Pa/K± 1.3 Pa/KNA
    Sampling Rate128 Hz157 Hz200 Hz200 Hz182 Hz100 Hz
    FIFO Size32 samplesNA512 Bytes512 BytesNA32 samples
    Current Consumption @ 1Hz1.7 uA2.7 uA2.7 uA3.4 uA4.2 uA8.5 uA


    From evaluating the specifications, BMP380 and BMP388 seem to be the best choices becasue they provide better absolute and relative accuracies, higher sampling rate, highest bit depth and higher absolute maximum pressure. The BME680 is special becasue it crams a pressure, temperature, humidity and air quality sensors in a single package. It might save some PCB real estate but can't compete with specs of other single purpose sensors, and it's going to cost higher than others. So we won't be using that. The DPS310 has its problems such as lower sampling rate, lower FIFO size etc, and it is priced similar to others. So these reasons also favor BMP380 and BMP388.

    Absolute accuracy is how close the output reading to the actual reading of absolute pressure (absolute pressure is the pressure reading taken with a zero pressure as reference). The more accurate the absolute pressure, more will be the accuracy of our calculated true altitude relative to seal level. So if we need more accurate altitude measurements we need more absolute accuracy. On the other hand, relative accuracy, as you guessed, is the degree of error between two relative pressure readings (absolute error on two relative readings will be same). This reading is crucial because it is what helps us to determine the relative elevation, for example how high a drone from the ground is etc.

    Temperature Sensor

    Most pressure and humidity sensors come with internal temperature...

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Enjoy this project?



David H Haffner Sr wrote 03/21/2018 at 07:39 point

Very nice 3D rendering!

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Vishnu M Aiea wrote 03/21/2018 at 08:36 point

Thanks. Did on Fusion 360 and rendered on the cloud :)

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David H Haffner Sr wrote 03/21/2018 at 09:06 point

Ha, I just re-designed my project using Fusion 360 and glad I did :)

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Vishnu M Aiea wrote 03/21/2018 at 09:16 point

The cloud rendering is a life saving feature. Gets 4000px final renders within 20 minutes of queue time.

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Andrej Mosat wrote 03/17/2018 at 22:34 point

I am interested in the mechanical and electrical construction of the keyboard. Any hints?

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Vishnu M Aiea wrote 03/18/2018 at 09:48 point

It's just a 3D model for now and that's how I want the keypad/keyboard to be. For prototyping we'll be 3D printing the enclosure and 3D printing the buttons not going to work I suppose. We'll need to make just the buttons with silicon or some similar material with which I have no experience. But for proto we'll do a makeshift keypad.

Do you have experience with making and integrating keypads ? I'm sorry, but I couldn't understand what you meant by "hints".

Thanks for showing interest and for the comment :)

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bobricius wrote 03/16/2018 at 13:07 point

Everything is nice nice, except display. Nokia 5110 display have very bad connection to board.

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Vishnu M Aiea wrote 03/16/2018 at 13:31 point

Yeah, I initially planned to use it becasue monochrome LCDs will offer better outdoor visibility under sunlight and also consumes only a little power. I plan to use 1.8" TFT LCD instead. 

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bobricius wrote 03/16/2018 at 13:38 point

look at eadogs displays, they are litle expensive but they have future, more sizes, muti color backlit and arduino compatible

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Vishnu M Aiea wrote 03/16/2018 at 13:34 point

I'll soon upload a current and better (revision 2) exploded view.

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Vishnu M Aiea wrote 03/16/2018 at 13:43 point

Thanks. Will check it out.

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Bayu Abi Pamungkas wrote 03/15/2018 at 08:02 point

great project bro, can't wait for it!

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Vishnu M Aiea wrote 03/15/2018 at 12:22 point

Thanks for the support :)

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SHIJITH A C wrote 03/14/2018 at 16:19 point

Great Work Bro,All the best.

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Aravind AJ wrote 03/14/2018 at 15:45 point

Cant Wait!

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althafa4786 wrote 03/14/2018 at 08:47 point

Day by day you your skill going up best wishes

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SYED JUNAID AHMED wrote 03/14/2018 at 06:42 point

All the best bro ,want to collaborate if possible

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Prasanth KS wrote 03/14/2018 at 04:00 point

Well done bro! 

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Vishnu M Aiea wrote 03/14/2018 at 06:42 point

Thanks :)

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SOORAJLALS wrote 03/14/2018 at 00:55 point


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Vishnu M Aiea wrote 03/14/2018 at 06:42 point

Thanks :)

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