Home-made electronic altimeter-variometer with the sound and light warning signals

    It can be used in aviation sports as an additional means of ensuring safety in:


    - performing parachute jumps;
    - flying on a paraglider;
    - flights on ultralight aircraft

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    Advantages of this solution:

    - a small price of components (1200-1500r at retail, when buying in China online stores is much cheaper);
    - ease of assembly (can be assembled in the evening, on a breadboard so generally in half an hour);
    - high accuracy of height measurement;
    - compactness and low weight of the device;
    - open program code (you can make changes, change the threshold settings for the operation of the device);
    - It can be used as a module for measuring atmospheric pressure (relative height, vertical speed and atmospheric pressure are constantly transmitted via the COM port).
    - Powered by both an autonomous DC power source (6-20V) and a Mini-B USB cable.

    Creation History:

    AltVar +, as I called it, was created on the basis of this project in the form of a variometer - tweeter. The prototype assembled on a breadboard. There were only two significant components on it:
    - Arduino Nano V3 microcontroller board
    - Gy-68 pressure sensor

    The device responded with a squeak to the ups and downs, but there was no indication. Therefore, I had to refine the program.

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    Now the board broadcast the values ​​of height and vertical speed to the computer's COM port.
    I wanted more autonomy and I added a 4-digital 7-segment display, enclosed a board with a sensor in a makeshift case, and built a battery into it. The display showed the value of the relative height.
    Now the instrument could be used both for measuring relative height and a high-precision barometer.

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    I used it for some time, because just a few minutes after turning it on, a tendency to change the weather was visible on it.
    The fact is that the accuracy of the sensor is approximately - + 0.17 m. The change in atmospheric pressure by a tenth of a mmHg. the column changes the meter reading by more than a meter.

    Friends and acquaintances of paratroopers knew that I had such a homemade product. They also pushed me to the next step, proposing on its basis to assemble a height signaling device - a “squeaker”.
    From the indication on a 4-digital 7-segment display, refused almost immediately, because if you hang them immediately 2, then the digital legs will be enough for me just barely, and the output code consumed MK resources "immeasurably." In addition, with this method of displaying, there is a noticeable stroboscopic effect, which spoils the visual perception of information.

    Displayed height and vertical speed data on - LCD - display 1602 (16 characters, 2 lines).

    So the trickster told me what to call him.

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    AltVar + regularly showed the slightest changes in height and vertical speed.

    To output an audio signal, I left part of the source project code .
    Tested it for days on end. AltVar + worked steadily.
    More truly - there was no failure! In the stand-alone version (with a 200mA 9V “Krona” type element), it worked for 8 hours without a break and turned off by power.

    The code for the microcontroller was created using the Arduino 1.0.6 compiler . In several stages, gradually adding functionality.

    The program algorithm works simply and straightforwardly:

    - values ​​of height and vertical speed are constantly displayed on the LCD-display;
    - the obtained values ​​of the height and vertical speed are compared with the threshold values ​​set by the user, and the results of this test give sound and light signals.

    When the device is turned on, the threshold values ​​of heights and speeds specified by the user are displayed. At first glance cumbersome - but informative!

    Video upload 1

    Changes can be made by changing the values ​​in the program and after compilation upload to the microcontroller.
    The algorithm of the program is built in such a way that before each jump you need to initialize AltVar + (turn it off - turn it on). We kind of “cock” it. What is it for?

    After the "cocking" we have:

    - the most accurate value of the zero height of the site;
    - the values ​​of the variables responsible for the number of sound signals take the initial values;
    - save battery power

    The program, as I have already indicated, is designed for skydivers. The "Chinese style" of writing allows even a beginner to understand it. Everything is simple and unambiguous, as it seems to me.
    I see no obstacles to adapt it for a paraglider (paramotor) and ALS.

    The program lines, as far as I could, provided with exhaustive comments.
    The “cap” indicates the necessary components, interconnections of elements, resistor ratings.
    You can open it in a text editor or in the compiler and see.

    In this version of the program, three heights are set for high vertical speed:

    - readiness (Ready) - 1 beep (set 1000 m);
    - alerts (Alert) - 3 sound signals (800 m);
    - alarms (Alarm) - a continuous sound signal (600 m).

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    The signal will be removed when the vertical speed decreases to a threshold speed (set - 25 m \ s). I have

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    entered two more informational sound signals:
    - when a certain altitude (Climb) is reached on board the aircraft ( 300 m at a vertical speed of more than +1 m \ s);
    - when reaching a certain height (Baza) during descent by parachute (200 m at a vertical speed of more than –1 m \ s, here the triggering height is limited to a minimum of 25 meters because on the ground after turning on AltVar + various unforeseen pressure surges are possible, which will cause signal);

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    Information is displayed in the format:
    1 line Alt: * * * * (meters) - (sign of negative height)
    2 line Var: * *. * (meters per second) -V- (decrease) + ^ + (rise) I
    used the standard compiler character generator, did not Russify. Therefore, everything is in English.

    In addition, all sound signals were duplicated by an LED.

    By connecting AltVar + via the COM port, you can use a third-party device to record a vertical flight profile. At first, I used this opportunity to debug the program and decided to leave it.
    To obtain the exact value of atmospheric pressure, it is necessary to amend the code variable reserved for these purposes. Then there will be extremely accurate readings of atmospheric pressure.
    Otherwise, the device without this correction provides measurements of height and vertical speed with fairly high accuracy.

    You can continue to build functionality.

    For example:
    - measuring the voltage of a power source;
    - record emergency data from the log (a kind of "virtual" SyPReS ");
    - put a vibrating alert;
    - etc. etc.
    But for now I have stopped on this set of signals.

    Assembly of prototypes for testing in the field.


    Soldered all AltVar + components on the breadboard,

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    placed the board under the LCD screen, which is certainly not a dogma. You can place it next to it. The appliance will become flatter but wider.

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    Made of 4 mm plastic housing for the device itself and for the battery (9V "Krona"). Processed joints and edges, blew out of an aerosol spray can.
    What can I say ... "Kondovo" happened.

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    Perhaps not compact enough. In fact, it was possible to use a small soap dish with cut-out holes for indicating, a switch and an audio connector. But what happened is what happened.

    There is something to test at least.

    The steps in this testing are as follows:

    - stability in static state;
    - autonomy check;
    - “elevator test” with very low threshold values ​​of heights and vertical speeds;
    - parachute jumps with elevated (in height) thresholds for the operation of the device

    Video 2 “elevator test” , significantly up to 1:45, then the box opened and the camera cracked
    it, in OK

    I think it was successful.

    Were asked:

    - response heights 20 => 15 => 10 m;
    - vertical speed -0.6 m \ s (at the limit of sensitivity);
    - the height in the set is 8 m;
    - descent altitude 5 m.

    When passing all altitudes, AltVar + “bleached” a specified number of times. And the LED blinked.
    After lowering the vertical speed below the threshold value - I removed the alarm. That is, he behaved quite predictably, as I planned.

    We will test it further.

    Almost anyone can assemble such a device if desired and, using an open source code, program it for their tasks.

    I summarize

    Components used:

    - Arduino Nano V3 microcontroller board
    - Gy-68 pressure sensor
    - LCD - 1602 display
    - 3.5 mm audio jack;
    - resistors 4k7, 1K, 330 ohms;
    - 5V LED;
    - “Krona” battery;
    - switch;
    - breadboard with conductors

    Software:

    - Arduino 1.0.6. , Connecting the library port, sensor, display and speaker
    - the sketch (a program that is loaded into the microcontroller)

    PS designed the dress, to simplify assembly AltVar +. But not yet made.

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    Paragliding firmware AltVar + v1.1

    Squeaks as an initial project, indicates height and vertical speed.
    Lights the LED at a decrease, even the minimum.

    AltVar + can also be used as a green LED flashlight :)

    Further development of this project (3.3-volt version)
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