Thermistor Sensor Module Help

Hello, I have bought this http://dx.com/p/thermistor-sensor-module-blue-199831#.Uy2Wc4VbtAc Thermistor sensor module and I have connected it to my Arduino UNO R3. I want to make a simple thermometer so I googled some tutorials on how to convert the value that the sensor outputs to temperature. I found a lot's of tutorials but none of them uses my module or something similar to it... I tried to use Steinhart-Hart Thermistor Equation from some of the tutorials but values are completely different than my room temperature. Can somebody help me? P.S: English isn't my first language so there might be some mistakes in my text.

There isn't much detail there about the interface, but it implies that this device provides a digital interface. Does it come with a manual or data sheet giving details? If not, figuring out how to use it will be tricky.

If all you want is a simple thermometer, a known reliable option would be a DS18B20 one-wire sensor, which costs about the same.

That card is digital… (unless the A0 gives you a voltage)
I guess you’ll be able to reach the analog voltage at one of the NTC legs.
That means soldering a new wire to one leg of the sensor and connect it to an analog input_pin
(choose the pin which is NOT gnd and NOT 5V)

The schematic may well match this one (with dual sensors)

It doesen't come with a manual or anything like that... It has 4 pins (VCC, GND, A0, D0). I think that if the D0 outputs HIGH or LOW signal depends on the voltage comparator and the A0 outputs voltage directly from the thermistor...

Try 'A0' to an analog input. If you get a reading that changes with temp, then u can use that card as thermometer. (if that reading is close to 500, its good. indicates that NTC is 10k @25degC in series with 10k resistor)

When I connect it to Analog input I get reading around 315 at 20 °C and it changes with temperature ( it decreases with rising temperature)

the unit uses a comparitor, not an op-amp.

This unit has 4 pins. the OO is the on/off pin that uses the comparitor like a switch. the A0 might be analog output.

http://playground.arduino.cc/ComponentLib/Thermistor#.Uy7ksKhdVQA

bring the A0 pin into an analog input on your Arduino and see what you get. IF it changed vales with temperature, then you should be able to follow the example,

attached file shows how a similar circuit work.
Can easily be changes to match your 10k 10k board (may your NTC be something different from 10K… like 20K)
(google translate for norwegian txt)
Beta for your NTC is probably around 4000

ardino-ntc-regning.pdf (83.2 KB)

I still can't get it to work... I'm getting some values, but certainly not the temperature of my room. Sometimes when I warm the thermistor the "temperature" in serial monitor decreases. In other tutorials it increases but it still isn't temperature not even close to my room temperature.

change the sketch so that you get 0-1024.

get a reading at room temperature. put it in the refrigerator, get a read.

with those to readings, you might be able to figure out what sensor is being used.

if you have a thermistor without using that board and use the help link

http://playground.arduino.cc/ComponentLib/Thermistor2#.Uy8YKahdVQA

The tutorial is based on R .. NTC swapped positions Rewrite one sentence in the file from previous post.. If that NTC is 22k @ 25deg C, then this code may be a starting point..

s=analogRead(A0); 
 tempc=1/(log(2.2*s/(1023-s))/4200.0+(1/298.15))-273.15; // beta = 4200
 Serial.println(tempc)

beta based on table for this one http://www.ebay.com/itm/NTC-Thermistor-100R-300R-1K0-5K0-20K-100K-3-5mm-/111199187400?pt=FR_YO_MaisonJardin_Bricolage_ElectroniqueComposants&var=&hash=item19e3fcf1c8 Does the NTC have any written text?

knut_ny: The tutorial is based on R .. NTC swapped positions Rewrite one sentence in the file from previous post.. If that NTC is 22k @ 25deg C, then this code may be a starting point..

s=analogRead(A0); 
 tempc=1/(log(2.2*s/(1023-s))/4200.0+(1/298.15))-273.15; // beta = 4200
 Serial.println(tempc)

beta based on table for this one http://www.ebay.com/itm/NTC-Thermistor-100R-300R-1K0-5K0-20K-100K-3-5mm-/111199187400?pt=FR_YO_MaisonJardin_Bricolage_ElectroniqueComposants&var=&hash=item19e3fcf1c8 Does the NTC have any written text?

It doesen't have any text on it (only text on the board is on the voltage comparator but that is irrelevant.) I tried your code an it shows 25 (°C) and that's pretty close to my room temperature so I will change some numbers and hopefully It'll work.

start with replacing the 2.2 +/- up to 10%
The table I found gave a hint for betavalue…: range 3900…4200
(measure a temp2 very different…fridge?. change beta to get close to temp2)
beware that the senor is slow… min two minutes to adjust to new temp