Share My Creation JG eVariometer (vertical speed indicator)

Discussion in 'Share Your Creations' started by freedom2000, Apr 28, 2019.

  1. freedom2000

    freedom2000 Well-Known Member Licensed User



    A friend of mine asked me to design a basic variometer for para gliding.
    He wanted a standalone device "beeping" when climbing.

    Here is the prototype (difficult to make more simple..) :
    • an ESP32 Lolin Lite board
    • a BMP280 sensor
    • a 3.3V buzzer

    and no solder, no PCB till now :)

    Of course a B4A App as I couldn't resist to design something a little more complicated... But bear in mind that the device really works standalone. The App is totally optionnal and transparent (no interface for binding, all automatic !)
    I took my scooter to ride the 2 roads down/up and back down/up.
    Variation of altitude is displayed in real time, using @Johan Schoeman excellent library


    I have added a menu to open Google Earth and display the track. (thank you @agraham :D)
    The altitude is given @1Hz by the sensor via BLE and lat/Lon by the GPS into the smartphone.
    A parameter allows to tune the altitude and correct the offset between sensor and Google Earth.
    The result is quite impressive. This tiny sensor is really accurate and stable (+- 50cm max).

    As you can see, I directly powered the BMP280 with 2 IO pins of the ESP32 It's possible because the BMP only sinks 5µA... + and Gnd are thus provided by 2 IO pins. If I switch them as inputs then the BMP is totally off. This should be nice when the ESP will be in deepsleep to protect the battery !
    Similarly the buzzer is sinking 14mA wich is a little too high for one single IO pin (12 mA max)... so I used 2 pins to drive the buzzer directly and safely.
    The Lolin32 board allows to plug a lipo bat and has a charger embedded (charge it or power it with a 5V USB charger).

    As such this design is really my most minimalistic one : (three componants !) and soooooo cheap (<10$) :rolleyes:
    Last edited: Apr 28, 2019
    fredo, Alexander Stolte, udg and 6 others like this.
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