Go Down

Topic: Aviation altimeter for microlights (Read 6399 times) previous topic - next topic

Hi !
I built this altimeter for microlights some months ago. Flight instructor in Paris (France) I was not happy with the bad quality of the classical (Chineese !) altimeters. They are expensive (300 to 900 EUR) and must be changed at least one time a year in a flying school.
This one is inexpensive (less than 100 EUR) is very easy to use and is more powerfull than standard altimeters. Our pilots love it and ask me to put one in all our aiplanes.
This project has been presented on the French forum. I hope you have many critics and proposals to ameliorate this project.
I have put the complete code with many comments for everyone interested to understand or to build their own altimeter.
Only one button to adjust and validate the Altitude or QNH, to switch between QNH and QNE and to switch back to QNH. Memory is also included to store the Altitude of your preferred airfield. You can change the units very simply, if you prefer meters rather than feet or inches of Hg rather than HPa.
On the Word sheet you can see 4 pictures: left/up : voltage and temperature (very usefull for microlights and very low cost) - right/up : the page for adjust the altimeter to local conditions (call an ATIS to have the actual QNH) - left/down : Altitude or QNH has been validated before takeoff. - right/down : flying at FL75 (7500 feet at 1013.25 HPa) You can notice that the color of pressure indication is different (now green rather than yellow)
On the bottom of the sheet I have included the schematics for wiring the different parts of this altimeter.

Waiting for your suggestions.


Hi !
This is the missing picture. The altimeter in the board panel.
The altimeter was installed in the body of the original altimeter (a lot of work !).
The encoder is now in the same place than the original button.
The microlight is a CTSW by Flight Design.



Very interesting!  Where is the sensor; inside altimeter body or elsewhere?

Hi !
Of course the sensor is in the body of the altimeter. So it is in the static pressure of the plane (with a nylon tube going to the static pressure hole).
The body of the altimeter is air-proof as before. I have just added two external connectors (air-proof also) for +12 V and Ground
at the bottom of the body to measure on-board battery voltage. A 7805 regulator is used to give  + 5V to the Arduino board.
Don't forget that onboard voltage can go up to 14.4 V which is to much for the Arduino but absolutely normal for the regulator.
The other advantage is to keep the sensor as close as possible of external air temperature which may be very different than the Inside temperature (heating in winter  as you can see on the picture... the heating command is  just above the altimeter !).



Love the "Caution: read manual before flight" sign.  I wonder if Apollo had that?!
[ I won't respond to messages, use the forum please ]


I like the "spins forbidden" sign - what kind of moron would try aerobatics in one of those?!


I like the "spins forbidden" sign - what kind of moron would try aerobatics in one of those?!


Hi !
Information about those crazy stickers :
"Caution: read manual before flight"  is a requirement of US Law !!!
"spins forbidden" : Spin recovery is not required for ultralights but there is no problem with !!!

Most ultralights are pretty well built and this one for example is the best seller in the US.
It is stronger than most aerobatics planes (with +9.6G at 450 kg  take-off weight and +7.2 G at 600 kg !) and faster than most certified aircrafts (more than 230 km/h, 130 knots)




I love aviation, feel free to post a link. Are you talking about one of those rogallo types or something else?

Hi !
No this ultralight is a multiaxis. Looks like a small plane.
You can visit : www.flightdesign.com/?  for more information.




OH, yeah I'm familiar with that, I almost bought one at an airshow one day. Those guys had a pretty good sales tactic :)


Your diy altimeter needs a certification I would say (ie. FAA - Aircraft Certification Service is concerned with the approval of software and airborne electronic hardware for airborne systems (e.g., autopilots, flight controls, engine controls), as well as that used to produce, test, or manufacture equipment to be installed on airborne products).. Will you pass it with arduino based system?

Hi !

Ultralights in France are not certfied planes so there is no need to pass FAA regulation.



Hi. I'm a pilot in Ireland and am really interested in building this project.  I haven't done anything with an arduino before, so I'm a bit tentative.  I've downloaded your code and the diagram.  I'm not sure which encoder you used.  Is there a part number for it?  I have sourced all the other bits.  Thanks for sharing this idea - I think it's brilliant. 


Hello Mike,

I think all encoder can work. You only need an encoder with a push-button contact.
I have forgotten to tell that the board was powered in 5 Volts with a 7805 (TO220)  regulator feed by the onboard 12 Volts battery.
A 1N4004 diode is inserted before the 7805 to prevent any error when connecting on the board power.
Do not try to use 12 Volts directly, this voltage may vary up to 14.4 Volts max which is too much for the arduino board regulator.
If you need any information, feel free to contact me directly.



Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131