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Here is a standalone altimeter working with Arduino that you can use in RC project, hiking, cars... where you want :)

It shows on first screen the altittude, the temperature & the air pressure, and in the second, the minimum / maximum altitude reached.

Parts needed: (~12$)

  • An arduino board like a nano, pro mini or even AtTiny85 (depends on what you want, pro mini is lighter than nano and can works with an input voltage of 3.3v to 12v, perfect for light weight RC) 3.29$ on ebay
  • BMP280 chip temperature & barometric pressure sensor 1.84$ on ebay
  • An OLED display (0.96" I2C IIC Série 128X64) 5.32$ on ebay
  • Iron solder, tin and wires
  • A plastic case to put all in 1.50$ on ebay

Step 1: The Wiring

The wiring is simple, the most "complicated" is to find the SCL and SDA pin on your arduino.

On the nano as on the photo, pin A4 is SDA and pin A5 is SCL.

On the Pro Mini, take a look at the picture, SDA is upside right to pin A2, and SCL upside right to pin A3.

Once your wiring is done, lets upload the sketch to the Arduino !

Step 2: The Program

Code explanations (full code below):

#include "U8glib.h"
#include "BMP280.h"

They are the 2 libraries you have to put inside Documents\Arduino\libraries\

#define P0 1021.97

This is where you calibrate the altimeter, changing this value. Once it's done, it's pretty accurate !

(by default it was 1013.25, i had to up it to 1021.97 to have the right altitude in my town)

U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NO_ACK);

Here you define the Oled screen type (128x64 etc...)

  u8g.drawStr( 5, 10, "Temp: ");
u8g.drawStr( 5, 30, "Bar : "); u8g.drawStr( 5, 50, "Alt : "); u8g.drawStr( 50, 10, sT); u8g.drawStr( 50, 30, sP); u8g.drawStr( 50, 50, sA);

Here the informations you want to display on first screen and their position ( Y, X, VALUE)

  dtostrf(A_MIN, 4, 2, sA_MIN);
dtostrf(A_MAX, 4, 2, sA_MAX); u8g.drawStr( 5, 20, "A Min: "); u8g.drawStr( 60, 20, sA_MIN); u8g.drawStr( 5, 45, "A Max: "); u8g.drawStr( 60, 45, sA_MAX);

Same for second screen

      if ( A > A_MAX) {
A_MAX = A; }
      if ( A < A_MIN || A_MIN == 0) {
        A_MIN = A;
      }

Here we update the minimum and maximun altitude stored

      do {
draw(T, P, A); } while ( u8g.nextPage() ); u8g.firstPage(); delay(1000);

Here, with the delay value (1000 in this case), you will stay 1 second on the first screen before switching to the second one. So change that if you want to customize display time :)

      do {
draw2(A_MIN, A_MAX); } while ( u8g.nextPage() ); u8g.firstPage(); delay(1000);

Same for second screen !

Hope it's clear, feel free to post a question in comments if needed !

Here is the full code:

#include "U8glib.h"
#include "BMP280.h" #include "Wire.h" #define P0 1021.97 //1013.25 BMP280 bmp; // OLED Type U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NO_ACK); char sT[20]; char sP[9]; char sA[9]; char sA_MIN[9]; char sA_MAX[9]; double A_MIN = 0; double A_MAX = 0; void draw(double T, double P, double A) { u8g.setFont(u8g_font_unifont); dtostrf(T, 4, 2, sT); dtostrf(P, 4, 2, sP); dtostrf(A, 4, 2, sA); u8g.drawStr( 5, 10, "Temp: "); u8g.drawStr( 5, 30, "Bar : "); u8g.drawStr( 5, 50, "Alt : "); u8g.drawStr( 50, 10, sT); u8g.drawStr( 50, 30, sP); u8g.drawStr( 50, 50, sA); } void draw2(double A_MIN, double A_MAX) { u8g.setFont(u8g_font_unifont); dtostrf(A_MIN, 4, 2, sA_MIN); dtostrf(A_MAX, 4, 2, sA_MAX); u8g.drawStr( 5, 20, "A Min: "); u8g.drawStr( 60, 20, sA_MIN); u8g.drawStr( 5, 45, "A Max: "); u8g.drawStr( 60, 45, sA_MAX); } void setup() { Serial.begin(9600); if (!bmp.begin()) { Serial.println("BMP init failed!"); while (1); } else Serial.println("BMP init success!"); bmp.setOversampling(4); u8g.setColorIndex(1); u8g.setFont(u8g_font_unifont); } void loop(void) { double T, P; char result = bmp.startMeasurment(); if (result != 0) { delay(result); result = bmp.getTemperatureAndPressure(T, P); if (result != 0) { double A = bmp.altitude(P, P0); if ( A > A_MAX) { A_MAX = A; } if ( A < A_MIN || A_MIN == 0) { A_MIN = A; } // Serial.print("T = \t"); Serial.print(T, 2); Serial.print(" degC\t"); // Serial.print("P = \t"); Serial.print(P, 2); Serial.print(" mBar\t"); // Serial.print("A = \t"); Serial.print(A, 2); Serial.println(" m"); u8g.firstPage(); do { draw(T, P, A); } while ( u8g.nextPage() ); u8g.firstPage(); delay(1000); do { draw2(A_MIN, A_MAX); } while ( u8g.nextPage() ); u8g.firstPage(); delay(1000); } else { Serial.println("Error."); } } else { Serial.println("Error."); } delay(100); }

Step 3: Now It's Up to You !

You can move form the breadboard to the plastic case with soldering all.

Then, put it on RC plane, RC quadcopter, RC helicopter..... or a water rocket !

Hope it was helpful and that you will send me a pic once it's done =)

<p>Hi everyone, I'm trying to run this but I can't even get past the verification of the code. I'm very new to this and I must be doing something stupid, any ideas?</p><p>The error is </p><p>error: 'bmp' was not declared in this scope</p><p> if (!bmp.begin()) {</p><p> ^</p><p>The first occurrence of the error is at line 4: BMP280 bmp;</p><p>but it continues anywhere &quot;bmp&quot; is mentioned.</p><p>Many thanks in advance, Paul</p>
<p>Hi Paul, you have this error because there is a problem with the &quot;BMP280.h&quot; library, verify that you have put the 2 libraries inside Documents\Arduino\libraries\ as in the Step 2: The program</p>
<p>Thank you so much Shoyun! :-)</p><p>I was being stupid!</p><p>Thanks again</p>
<p>You are welcome ! Glad to help you :) </p>
<p>Hi </p><p>how to set the QNH?</p>
<p>Hi alainn, to calibrate the altimeter (if i understand you well) you have to play with the P0 value in the begining of the code: #define P0 1021.97 </p><p>Change the 1021.97 value to match your real altitude, then it's calibrated and acurate :)</p>
Hi Shoyun<br>you need a computer to do that <br>not very convenient<br>this one use a tactil switch <br> http://electro.olganet.com/2014/03/29/tiny-altimeter-oled/ <br>but not convenient also<br>an encoder should be nice to set the QNH or QNE <br>so you should use your device as a true altimeter in a plane
<p>Hi ! You are right, you need a computer but once the setting is done if you stay at the same place it will be ok :)</p><p>For my purposes it was enough, maybe you need the ability to set up on the go, it may be possible to add it.</p>
<p>Nice project </p><p>How could I change the delay to put a button?</p>
<p>Hi, i don't undersand what you really want to do, sorry.</p>
there is a delay to change the screen (one second) <br>I want to put a button instead of the Delay to change the screens<br>How can I do it?
<p>Hello! Is there an option to see the history of the altitude using that method?</p><p>Thanks</p>
<p>Hi !</p><p>The screen auto switch from current data and min / max altitude every second. No history but min and max altitude values.</p><p>It could be done writing on a sd card current data every x seconds :)</p>
<p>Nice project </p><p>How could I change the delay to put a button?</p>
<p>One other minor detail was that I had to put both CSD and SDO (on the BMP280) to +3.3 to get it to work. In your diagram you showed SDO going to GND when I did that it did not work... Now to get it packaged up and on top of a water rocket!</p>
Oh ok, maybe something different in our chips. Nice that you found the solution, it can help others :)<br><br>When you will finish your water rocket send a picture ! =)
<p>Got it working! The problem was in the BMP280.h file. The I2C address was 0x76 and my BMP280 was on 0x77. Once I ran the I2C scanner I was able to correct the BMP280.h lib file with the correct address and then it worked fine!</p>
Glad to read that :))) Nice !
<p>I am having problems. I tested the display and the BMP280 separately and they work fine. (Note: using a different library for the 280 Adafruit_BMP280.h) But when I try and run your script all I see is a bunch of small pixels on the screen.</p><p>Please advise... Thanks Bill</p>
Hi Bill.<br><br>If you changed the library used, u maybe have to adapt my code, why don't you use the library i mentioned ? Not compatible ?<br><br>Hope you will managed to make it work.
<p>Hopefully you saw that I did get it working.. But yes there was a problem with the original library with the I2C address. I was able to correct it and now it's working... I did not even try and get it working with the Adafruit_BMP280.h it is very different.</p>
<p>This is a pretty cool idea. For practical purposes for RC or rockets, how small of a bundle do you think you could fit all of these components into?</p>
<p>Thanks :)</p><p>It can be really small and light weight with an Attiny85 or nano. I can't tell u exactly but i'm sure that it will be small enough !</p>

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