Thermistor shield from arduino-direct

Using Arduino Programming Questions
1

Hello,

I'm a software developer, but I'm also a total newbie in electronic. I've bought the thermistor shield from arduino-direct. When I try to read the value, I always get 142 ±1. Nothing happens even when I try to heat the thermistor with my fingers.

Is there any tutorial using this shield?

Thank you

2

Having posted several times now, you should be aware of the drill. Where is the link to the shield/device/whatever that is causing the problem? Where is the code that is not performing as intended?

3

Wasn't aware there was a way to post questions.

Where : http://arduino-direct.com/sunshop/index.php?l=product_detail&p=39
What : Thermistor 103 with a LM358 chip and some resistors.

Code :

int thermPin = A0;
float thermValue = 0;

void setup ()
{
  Serial.begin (9600);
}

void loop ()
{
  thermValue = analogRead (thermPin);
  Serial.println (thermValue);
  delay (1000);
}
4

I've found the code from a Chinese web site, but it still gives only 9 as a value.

http://translate.google.ca/translate?js=n&prev=_t&hl=fr&ie=UTF-8&layout=2&eotf=1&sl=auto&tl=en&u=http%3A%2F%2Fitem.taobao.com%2Fitem.htm%3Fid%3D6208909767&act=url

#include <math.h>

double Thermister (int RawADC) {
 double Temp;
 Temp = log (((10240000/RawADC) - 10000));
 Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp));
 Temp = Temp - 273.15; // Convert Kelvin to Celcius
 Temp = (Temp * 9.0) / 5.0 + 32.0; // Convert Celcius to Fahrenheit
 return Temp;
}

void setup () {
 Serial.begin (115200);
}

void loop () {
 Serial.println (int (Thermister (analogRead (A0)))); // display Fahrenheit
 delay (100);
}
5

Rather than all that complicated code, see if you are reading anything from the analog pin.

int thermPin = 0; // NOT A0 (A0 is a digital pin)

void setup()
{
   Serial.begin(9600);
}

void loop()
{
   Serial.print("Analog pin reading: ");
   Serial.println(analogRead(thermPin));
   delay(100);
}

If you don't get different readings as the temperature changes, the problem is with the hardware. If you do get different readings, the problem is with the software.

6

I know it's been a while, but I didn't touch my arduino for a while.

I figured out that arduino-direct don't always follow wire color standards. After checking the PCB, I noticed that they flipped their cables color. The black wire is for signal and the white as the ground...

Now it works, I only need to converted the value to human readable.

Thanks

7

I have a bunch of bricks from arduino-direct, they are made by Flamingo EDA. Look on the underside of the printboard. Mine all have - + and S markings, so no problem to connect them...

8

Hmmm... I have check all my bricks from them and I don't see the + - s markings. They might have add them lately.