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MAX31855 problem - reads zero
Moderators: adafruit_support_bill, adafruit

MAX31855 problem - reads zero

by hb2013 on Thu Jun 20, 2013 5:55 pm

Can't get MAX31855 to read anything other than zero. Below is the code I am using.

Code: Select all | TOGGLE FULL SIZE
#include "Adafruit_MAX31855.h"
int GND = 4;
int VIN = 2;
int thermoDO = 5;
int thermoCS = 6;
int thermoCLK = 7;

Adafruit_MAX31855 thermocouple(thermoCLK, thermoCS, thermoDO);
 
void setup() {
  Serial.begin(9600);
  pinMode(GND,OUTPUT);
  digitalWrite(GND,LOW);
  pinMode(VIN,OUTPUT);
  digitalWrite(VIN,HIGH);
 
 
  Serial.println("MAX31855 test");
  // wait for MAX chip to stabilize
  delay(500);
     if (digitalRead(V3OUT)) {
      Serial.println("MAX31855 V3 IS HIGH");
    }
}

void loop() {
  // basic readout test, just print the current temp
   Serial.print("Internal Temp = ");
   Serial.println(thermocouple.readInternal());

   double c = thermocouple.readCelsius();
   if (isnan(c)) {
     Serial.println("Something wrong with thermocouple!");
   } else {
     Serial.print("C = ");
     Serial.println(c);
   }
   //Serial.print("F = ");
   //Serial.println(thermocouple.readFarenheit());
 
   delay(1000);
}
Last edited by adafruit_support_bill on Thu Jun 20, 2013 7:52 pm, edited 1 time in total.
Reason: Please use the 'code' button when submitting code
hb2013
 
Posts: 4
Joined: Thu Jun 20, 2013 5:47 pm

Re: MAX31855 problem - reads zero

by adafruit_support_bill on Thu Jun 20, 2013 7:53 pm

What thermocouple are you using? Is it grounded? Post a photo or wiring diagram.

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Posts: 37497
Joined: Sat Feb 07, 2009 10:11 am

Re: MAX31855 problem - reads zero

by hb2013 on Thu Jun 20, 2013 8:56 pm

Here are the pics. I am using K-type thermo-couple.
Attachments
arduino-max2.jpg
arduino-max2.jpg (33.04 KiB) Viewed 7487 times
arduino-max1.jpg
arduino-max1.jpg (34.64 KiB) Viewed 7487 times
hb2013
 
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Re: MAX31855 problem - reads zero

by adafruit_support_bill on Thu Jun 20, 2013 9:34 pm

Is it grounded?

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Re: MAX31855 problem - reads zero

by hb2013 on Thu Jun 20, 2013 9:57 pm

Do you mean thermocouple? It has two wires connected as shown. Ground what? The probe?
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Re: MAX31855 problem - reads zero

by adafruit_support_bill on Fri Jun 21, 2013 5:45 am

Ground what? The probe?

If the junction is in contact with a grounded object, it will read 0 with this amplifier.

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Re: MAX31855 problem - reads zero

by hb2013 on Fri Jun 21, 2013 10:37 am

No it is not. It is seating on a wooden surface.
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Re: MAX31855 problem - reads zero

by adafruit_support_bill on Fri Jun 21, 2013 11:06 am

Your connections look ok. Contact support@adafruit.com with a link to this thread and we can send you a replacement.

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Re: MAX31855 problem - reads zero

by jerm2119 on Wed Jun 26, 2013 12:42 pm

I have a similar problem. Using the arduino 1.0.5 software and an adruino uno, the serial monitor output is -127.94 Celsius regardless of where the thermocouples are. There is also a message saying "Something wrong with thermocouple!" I've checked the wiring and even if the wires were reversed, that number is not possible at room temperature. Help?
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Re: MAX31855 problem - reads zero

by adafruit_support_bill on Wed Jun 26, 2013 2:09 pm

That sounds more like a problem with the thermocouple than the MAX31855. Where did you purchase these? I don't see you in the customer database.

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Re: MAX31855 problem - reads zero

by paddygoat on Wed Jul 03, 2013 9:00 am

Just recieved my MAX31855 breakout board (invoice no. 303135) and wired it up BUT getting - Int. Temp = -127.94 and T/C Problem BUT I tested the thermocouple on a rocket scream MAX31855 board and it works fine. Please advise .... Thank you.
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Re: MAX31855 problem - reads zero

by paddygoat on Wed Jul 03, 2013 9:11 am

Also, there is a problem finding the avr folder. Just got the board working with the serial version of the software, but quite a few 'thermocouple errors'.
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Re: MAX31855 problem - reads zero

by adafruit_support_bill on Wed Jul 03, 2013 9:32 am

Contact support@adafruit.com with a link to this thread to arrange for a replacement.

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Re: MAX31855 problem - reads zero

by paddygoat on Wed Jul 03, 2013 9:36 am

It's the code that was not working actually. Got it working by replacing with this:

#include "Adafruit_MAX31855.h"
#include <LiquidCrystal.h>

int thermoDO = 3;
int thermoCS = 4;
int thermoCLK = 5;

LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

Adafruit_MAX31855 thermocouple(thermoCLK, thermoCS, thermoDO);

void setup() {
Serial.begin(9600);
lcd.begin(16, 2);

Serial.println("MAX31855 test");
// wait for MAX chip to stabilize
delay(500);
}

void loop() {
// basic readout test, just print the current temp
Serial.print("Internal Temp = ");
Serial.println(thermocouple.readInternal());

double c = thermocouple.readCelsius();
if (isnan(c)) {
Serial.println("Something wrong with thermocouple!");
} else {
Serial.print("C = ");
Serial.println(c);
}
//Serial.print("F = ");
//Serial.println(thermocouple.readFarenheit());

lcd.setCursor(0, 0);
lcd.print("Int. Temp = ");
lcd.println(thermocouple.readInternal());
lcd.print(" ");
lcd.setCursor(0, 1);
lcd.print("C = ");
lcd.print(c);
lcd.print(" ");

delay(1000);
}
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Re: MAX31855 problem - reads zero

by adafruit_support_bill on Wed Jul 03, 2013 9:43 am

Interesting. The thermocouple part of that code looks identical to the serialThermocouple example.

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