Author Topic: Question about Arduino board  (Read 4636 times)

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Offline cloneTopic starter

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Question about Arduino board
« on: January 12, 2009, 11:07:03 PM »
I'm looking to buy an arduino duemilanove board as my very first microcontroller!

I want to hook up a thermistor as a sensor on one of the analog inputs.  the thermistor's resistance will change depending on the temperature.

my question is this.. on the spec sheet at the arduino website it says "The Duemilanove has 6 analog inputs, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts"

so.. are the analog inputs going to be able to read the change in resistance, or do those inputs only measure a voltage???

any help is very appreciated, im NEWB!

Offline cloneTopic starter

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Re: Question about Arduino board
« Reply #1 on: January 12, 2009, 11:32:47 PM »
i think i might have found the solution... 1 lead of the thermistor would be connected to +5V, and the other lead of the thermistor would be connected to an analog input.

depending on the resistance of the thermistor, it would give a reading at the analog input of something between 0 and 5 V. 

sound correct?

Offline frodo

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Re: Question about Arduino board
« Reply #2 on: January 13, 2009, 03:36:50 PM »
yes, it sounds right. try it out with your arduino board and tell us whether it works or not. :) Dan
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Offline TheWire

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Re: Question about Arduino board
« Reply #3 on: January 13, 2009, 09:34:51 PM »
Connecting the thermistor to +5v and the analog input will show a +5v reading at the input regardless of the temperature.  You will need a voltage divider or other circuit to get a voltage vs temperature reading for the Arduino.  Google "Thermistor Microcontroller" or "Thermistor Divider" for a lot of info.  A good example is: http://www.doctronics.co.uk/voltage.htm.

Also, thermistors tend to be very non-linear and you will have to correct for this to get an accurate temperature reading.

Offline Razor Concepts

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Re: Question about Arduino board
« Reply #4 on: January 13, 2009, 09:39:11 PM »
If you want slower, but more accurate readings you can go with small temperature sensors. I've used a LM335AZ, a temp sensor in a standard transistor-like package and it works great. And like TheWire said, you'll need a voltage divider which can be just a resistor.

Offline cloneTopic starter

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Re: Question about Arduino board
« Reply #5 on: January 14, 2009, 03:06:17 PM »
sweet! the voltage divider answere is bang on what i needed to know.  thanks!

 


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