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Topic: Open Source Data Logger Project Using the Arduino? (Read 37 times) previous topic - next topic

AVRman

It's great that you brought this up. I'm actually working on using an Arduino to store data off to a USB thumb drive. I'm logging from one USB port and saving to the thumb drive. Just need to get the closing of files working correctly.

Zujin

I'm a co-op student working for a company right now and am highly interested in working on this project.  I do have some questions about the actual operation of the data logger though.
1.  How good is the resolution? I know it's 10 bit, but what is the max value for the analog input? Our main need here is thermocouples and 1 mV can be 20 degrees difference or more.
2.  How could we get more inputs?  I know you can get more boards or more A/D converters and then put them on the digital ins, I was just wondering if there was an easier way to do this?

My main goal is to get as many thermocouple inputs as possible.  Any code I write, no matter how "dirty" would be posted back.

Sorry if most of the questions have been answered elsewhere, I'm just now getting into the arduino board community.  Most of my experience is with Linux based microcontrollers.

Thanks.
Ryan
Tenn. Tech U.
Ryan C
Tenn. Tech U


mem

Hi Ryan, by default the arduino uses 5 volts for the ADC reference.  As I recall from the datasheet, you can use an internal reference of 1.1 volt giving about 1mv resolution. The guaranteed accuracy is  plus/minus 2 bits.

There are six analog inputs and you can add an external multiplexer if you need more.

phill

Has anybody taken on this project? I have a few ideas for a modular system. I think better resualts could be gained by using standalone ADC chips, combined with a modular system, you could just plug in the modules you need!

kg4wsv

hey Ryan,

Maxim has a couple of thermocouple interfaces (MAX6674 MAX6675) that would attach to the Arduino via SPI.  Since SPI is a bus, requiring a separate chip select for each device, you could easily put a dozen or so on an Arduino as-is.  With an IO expander IC you could add even more.

I've got these on my list to play with, but haven't had time yet.

-j

(TTU class of '90)

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