Humidity sensor SHT2x for ArduPilotMega

I have implemented an i2c temperature+humidity sensor on my ArduPilotMega. This could be useful for anybody, so I will try to explain here how I did it.

What is needed:

the sensor i used is the SHT21 from Sensirion, but it should also work for the SHT25. On the manufacturer website you can find technical data about the sensors, and they also sell their sensors themselves:

I received the sensor from Sensirion mounted on a breakout board.

a connector to easily change the sensor breakout borad.I used one from samtec(ref SMS-104-01-G-S).

An I2C/SMBus Voltage Traslator (I2C Level Shifter) With adapter because the sensor uses 3.3V i2c when the APM outputs 5V

An EM-406/uBlox/MTK Adapter Cable 10 cm , or whatever length.

(only 4 wires are required. So you can remove the red one and the black one standing next to it)

Code:

I did include all the files I modified here.

Code features:

-I did not implement mavlink code for data transmission. It seems it requires changes in Mission Planner, which I cannot do.

-In the Command Line Interpreter (CLI), in the test "menu", the "meteo" command output temperature and humidity, until "enter" is pressed.

-It can log temperature and humidity about every second (I have to check if the logging interval is really 1 sec). The logged data can be retrieved in Mission Planner. Logging can be enabled or disabled in the "logs" menu.

So far it seems to work fine. I will test more in the next days.

a) ArduPilotMega.pde

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Comments

Dom April 14, 2012 at 10:45pm

Eric,

If you're still around, could you post a new download link to this code?
Seth November 11, 2011 at 4:41pm

For a high altitude balloon/UAV drop example check out the Near Space Corporation.
Andrew Beckett October 21, 2011 at 3:43pm

I got it, thank you!
Eric October 21, 2011 at 12:12pm

Andrew

I have uploaded the file on a third party web service, accessible from the same link as before. Probably the link will not stand forever, so don't wait too much.
Andrew Beckett October 19, 2011 at 3:28pm

I'm interested in seeing the code. Do you have another web host you can use?
Eric October 19, 2011 at 1:41pm

Scott

Yes that could be a good solution for meteorological stations. I would rather go for a fixed wing UAV, as the wind can blow your balloon 50 km away in windy conditions.

Some gps might also not work at very high altitudes, due to limitations of manufacturers. very high speed can also be a limitation, when the balloon blasts at about 30km, the UAV would fall faster than sound speed.
Eric October 19, 2011 at 1:33pm

Andrew

I tried a few times to uplaod the file again, with no success :(. I don't know what I do wrong.

If you are interested I can send you the source code.
Scott Plunkett October 19, 2011 at 12:43pm

@Eric...brings up an interesting thought - What about an instrument package / Quadrotor attached to a balloon...balloon goes up and measurements are taken / logged, then at a given altitude the system performs a cutaway, free falls most of the trip down, then pops a parachute for deceleration and to right the quad, then the quad performs a RTL function landing at the launch point No more lost expensive instrument packages / radios; could be a fun / interesting project.
Andrew Beckett October 19, 2011 at 12:32pm

Download link is broken.
Rana October 1, 2011 at 6:50pm

Nice attempt, could be very useful for measuring the temperature of the Lipo in flight.

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