Altimeter (altitude Meter) Based on Atmospheric Pressure

[Edit]; See version 2 in step 6 with manually baseline altitude input.

This is the building description of an Altimeter (Altitude Meter) based on an Arduino Nano and a Bosch BMP180 atmospheric pressure sensor.

The design is simple but the measurements are stable and quite accurate (1m precision).

Every second ten pressure samples are made and the average of these ten is calculated. This pressure is compared to a baseline pressure and is used to process the altitude. The baseline pressure is measured at the moment the altimeter is powered on so this represents an altitude of zero meter. If necessary the baseline pressure can be reset by pushing the button.

[Edit]: Version 2 has manually baseline altitude input. See description in Step 6

During setting the baseline (power on or button push) the current atmospheric pressure is displayed for one second. After this the altitude is on the 4-digit display and this will update about every second.

A red led is used for negative altitudes when going down-hill after setting the baseline.

[Edit]: With Version 2 this represents negative altitudes so below sea level.

The altimeter is powered by an USB cable so can be used in a car, motorcycle or on every other place with USB or a power bank.

Two special libraries are used. One for the BMP180 that can be found here. And one for the TM1637 4-digit display that can be found here.

The BMP180 is not the newest version. It seems to be
replaced by the BMP280. It should be simple to replace the BMP180 with the BMP280 in this design.

Parts of the sketch are based on the “BMP180_altitude_example.ino” delivered with the BMP180 library.

Step 1: Breadboard to Test the Design

I started with an Arduino Uno to test the design. In the final version I used a Nano because it's smaller.

Step 2: Board Creation and Housing

One single board is used. The cover of the housing holds the button, the led and the 4-digit display.

Step 3: Arduino Pin Connections

Connections for BMP180:
GND - GND
VCC - 3.3V (!!)
SDA - A4
SCL - A5

Connections for 4-digit TM1637 display:
GND - GND
VCC - 5V
CLK - D6
DIO - D8

Led voor negative values - Down-hill: D2

Button for reset baseline pressure: D4

Step 4: The Arduino Sketch

Step 5: Final

This is the result...

Step 6: Version 2 With Manually Baseline Altitude Input

In this version one extra button is introduced. Button 1 (black) is to start manually baseline altitude input. Button 2 (white) is to increase the value per digit.

Sequence during altitude input is:

Button 1 pushed - Led flashes 1 time - button 2 can be used to increase x digit in 000x

Button 1 pushed again - Led flashes 2 times - button 2 can be used to increase x digit in 00x0

Button 1 pushed again - Led flashes 3 times - button 2 can be used to increase x digit in 0x00

Button 1 pushed again - Led flashes 4 times - button 2 can be used to increase x digit in x000

Button 1 pushed again - Led flashes 5 times - button 2 can be used to change the sign: led_on=negative (below sea level), led_off=positive (above sea level)

Button 1 pushed again - Led flashes 1 time long - baseline altitude input ready

Step 7:

Sketch of version 2.

Comments

[k3po.mcdonald]

I want to build this but also have the display show density altitude based off a calculation involving the dew point and relative humidity. would love to learn the source for components such as the sensor, and cabinet.

[jaapdubbelaar]

Hello, Most of the parts for this kind of projects I order from BangGood.com. Try this search for the pressure sensor: https://www.banggood.com/search/bmp180.html?from=nav The cabinet was bought in a local electronics shop.

[k3po.mcdonald]

Thank you for responding. I ordered a BME280 and a project box off of Amazon. Did you by chance post the example code? I'll obviously have some mods I will need to do but I'd love to have a headstart. I'm also going to be using a different display. Long-term goal is to display altitude, density altitude, Outside Air Temp and rate of change over time (ft per minute rise or fall) . This is all to be put on an experimental aircraft.

[jaapdubbelaar]

Hello, Your project sounds very interesting. What kind of aircraft is it? Do you have any info online I can see?
You asked for the example code. This is on the Instructable page. See Step 4 (the initial version) and Step 7 ( Version 2 With Manual Baseline Altitude Input).

[k3po.mcdonald]

The second version will not open in IDE. can you post somewhere the text?

[jaapdubbelaar]

I added also .txt versions of the codes to Step 4 and Step 7. Does this help you?

[k3po.mcdonald]

Yes perfect! Thank you. I now have something to understand coding to change the base. I also will have to figure out how to modify it from the display you used to the one im using and the BME280. Also want to factor in the variometer coding as well.

[MikeL90]

This really is of no use at all. It must be able to manually set the current height above sea level when it is powered on, otherwise it only works when you live by the sea!!

[jaapdubbelaar]

Hello Mike,

Version two is ready!
You can manually set the current altitude now.
Please take a look here

What do you think?

[jaapdubbelaar]

Thanks for your reply, Mike.
You are right but a do live about at sea level in the Neherlands :-)
Manually setting the current height is a good idea for version two.