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[on:]

Hi there,
i want to build myself an arduino driven pressure and temperature logger to use while scuba diving. It should have the following features:
-Turn on automaticly when i get into the water
-Adjust the pressure sensor (so it gives correct readings no matter what alttitude I dive in) when it powers on.
-Log time, temperature and pressure on an SD card
-Flash a warning LED when the temperature drops below 6°C
-Turn back of after getting out of the water.

I found this http://www.adafruit.com/products/243, which should cover the SD card and clock, http://www.adafruit.com/products/391 for the pressure (depth), and http://www.adafruit.com/products/381 for the temperature.

Everything will be housed in an aluminium housing.

Could you guys give me advice on which Arduino to use, that would cover this project? I'm totally new to this so I have no idea on what to use...

Thanks
ChoKo

[Reply #1 on:]

i want to build myself an arduino driven pressure and temperature logger to use while scuba diving.

I'd be more worried about getting a case that could hold it properly... and dry.

[Reply #2 on:]

some of the stuff its really easy to do like

Log time, temperature and pressure on an SD card
Flash a warning LED when the temperature drops below 6°C

and could be done on every arduino i think

as for powering on/off  -  not really sure how to do it - you could get the altitude reading from the pressure sensor and based on the altitude turn the device on/off but it maybe harder than it looks cause the altitude reading its based on the see level pressure and i think the pressure will change with your altitude so the calculation may not be so exact

but one question putting the sensor (pressure sensors) in an airtight case will not cause problems ?
also if you want a smaller data logger check this out http://www.sparkfun.com/products/9530

hope this helps

[Reply #3 on:]

Have a look at Seeeduino's Stalker.
It's a Arduino especially for data logging. Its have at on-board SD card slot, a RTC chip and a on-board temperature sensor.

http://www.seeedstudio.com/depot/seeeduino-stalker-v2-p-727.html?cPath=132_133

Actually they do also have a temperature data logger example code on there website. So with some mirror changes i think it could be a good starting point for your project.

http://www.seeedstudio.com/wiki/Seeeduino_Stalker_v2.0#Source_Code_Examples

[Reply #4 on:]

Check with member Packhorse (in new Zealand) too - he is working on a similar device already. I think jest need to add an SD driver/socket to it, like the functionality of the adafruit shield.

[Reply #5 on:]

Ok, thanks for the replies. I had a look at Packhorses project and i think that with some slight modifications I should be able to turn it into what I want 
About the pressure sensor: I think Putyn is right about the sensor in an enclosed case. Will try to think of something to do about that...

Cheers,
ChoKo

[Reply #6 on:]

About the pressure sensor: I think Putyn is right about the sensor in an enclosed case.

As well as reading the pressure inside a pressure sealed box your requirements pose a few other challenges.
Seeing the warning LED through the aluminium is going to be tricky. Reading the temperature through the metal should be possible but the reading will be delayed. Getting the processor which is off to detect when the dive starts and turn itself on seems to need time travel (okay you could have some electronic circuit that switches the processor on when electrodes get wet, but that's making things complicated). Reading the surface atmospheric pressure, to adjust for altitude, after the dive has started also needs a bit of time travel.

I think life would be a lot simpler if you just turned the thing on/off manually.

Take a look at your depth gauge. I imagine it is liquid filled and has a transparent face which, when pressed, causes the pressure reading to change. You might want to consider if you could do something similar putting the arduino inside a container filled with inert non-conducting liquid, flexible transparent front to transmit pressure and allow led to be seen, thin metalic foil transmitting heat from exterior to temperature sensor surface. 

Some dive watches are liquid filled. I bet that some dive computers are too.