deported air speed sensor

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deported air speed sensor

Post by jfpion » Mon Oct 15, 2018 9:06 am

Hello , I would like to use an air speed sensor on my (rather) big plane (2.7 m biplan).
but I need to install the pitot on the wings, I would like to install the sensor in the wings (outside of the propeller wind) because it is easier tou connect a wire than 2 tubes . and like I want to monitor the 3 batteries for the RC and ignition , it would be a lot of wiring to install all the openxsensor in the wing.
the question is how long can be the connexion wire between the arduino and the 4525DO ?
thank you

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Re: deported air speed sensor

Post by Kilrah » Mon Oct 15, 2018 9:10 am

I'd just recommend using 2 separate oXs, one in the wing just for airspeed and one in the fuselage for the rest.

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Re: deported air speed sensor

Post by jfpion » Sat Nov 03, 2018 7:07 am

thank you, for this plane it could be done, but for others like gliders it will be tricky . and the question remains what is the max length for the wiring between the arduino ant the 4525do (or the others devices) ?

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Re: deported air speed sensor

Post by mstrens » Sat Nov 03, 2018 7:43 am

It is difficult to say what is the max length because it depends on the capacitance of the cable and of the noise environement.
Based on some article in google about I2C, I expect that you it should work for a cable lentgh of 1.5m.
Currently oXs is configured to work at 400kkz but it could easily be adapted to work at 100khz in order to let it works with a long cable.
Adding some pull up resistances could also help.

So I expect you can go for it.

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Re: deported air speed sensor

Post by devil » Sat Nov 03, 2018 9:29 am


I asked myself the same question two years ago.
and made a test with 5m silicone cable 30AWG ...
I split my OXS sensor into two parts.
The Arduino Pro mini with power measurement sits in the front of the canopy, easily accessible for flashing.
The second part with MS5611 and Do4525 is in the rudder at the end of the fuselage.
Used OXS Sketch Version 7
Pullup resistors, I have no built-in and no capacitors.
Everything directly 1:1 wired
it is also a second RX installed at the end of the hull and this does not bother the I2C.

The reason was I did not want to put 2m tubes through the hull for the Airspeed and the compensated Vario.


Although I only needed 2m cable but I wanted to know, so the 5m cable to test.
with 5m silicone cable 30AWG I had no problems at the table, since I only needed 2, I was sure that it works.

Here is a photo of the test composition :shock:
And here are a few photos of the finished sensor that is installed since last year in my glider and works very well.
I twisted the cables in the fabric hose

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