MAX31855 throwing crazy numbers

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dougt2
 
Posts: 1
Joined: Fri Jul 26, 2013 4:28 pm

MAX31855 throwing crazy numbers

Post by dougt2 »

My max31855 starting throwing off weird numbers and gave me some really roasted coffee. I've set it up to test with just the arduino and the max on a different breadboard and am running the serial test and here's what some of the results look like:


Internal Temp = 0.00
C = 257.00
F = 32.00
Internal Temp = 0.00
C = 64.25
F = 32.00
Internal Temp = 0.00
C = 16.00
F = 32.00
Internal Temp = 64.00
C = -2048.00
F = 32.00
Internal Temp = 16.06
C = 514.00
F = 32.00
Internal Temp = 0.00
C = 0.50
F = 32.00
Internal Temp = 2.00
C = 0.00
F = 147.20
Internal Temp = -0.50
C = 0.00
F = 32.00
Internal Temp = 0.12
C = 1028.00
F = -3654.40
Internal Temp = 16.00
C = 0.00
F = 35.60
Internal Temp = 4.00
C = 128.50
F = 32.00
Internal Temp = 0.00
C = 0.00
F = 32.00
Internal Temp = 0.00
C = 0.00
F = 32.00
======================================================
I changed the Thermocouple to another I had and now get:

MAX31855 test
Internal Temp = 48.19
C = 1538.00
F = 1886.00
Internal Temp = -0.50
C = 16.00
F = nan
Internal Temp = 4.00
Something wrong with thermocouple!
F = 263.30
Internal Temp = 32.06
C = 2.00
F = 1882.40
Internal Temp = 0.50
Something wrong with thermocouple!
F = nan
Internal Temp = 4.00
Something wrong with thermocouple!
F = 263.30
Internal Temp = 32.13
C = 1030.00
F = 1882.40
Internal Temp = 1.00
Something wrong with thermocouple!
F = nan
Internal Temp = 4.00
Something wrong with thermocouple!
F = 263.30
Internal Temp = 32.13
C = 1028.00
F = 1882.40
Internal Temp = 1.00
Something wrong with thermocouple!
F = nan
Internal Temp = 4.00
C = 128.50
F = 493.70
Internal Temp = 32.13
C = 1028.00
F = 39.20
Internal Temp = 1.00
Something wrong with thermocouple!
F = nan
Internal Temp = 4.00
Something wrong with thermocouple!
F = 495.50
Internal Temp = 32.13
C = 1028.00
F = 39.20
Internal Temp = 1.00
Something wrong with thermocouple!
F = nan
Internal Temp = 4.00
C = 128.50
F = 32.00
Internal Temp = 32.13
C = 1028.00
F = 39.20

Suggestions?

User avatar
adafruit_support_bill
 
Posts: 88096
Joined: Sat Feb 07, 2009 10:11 am

Re: MAX31855 throwing crazy numbers

Post by adafruit_support_bill »

Post a photo showing your soldering and connections.
Make sure that your thermocouple junction is not grounded. The junction should not be in contact with any grounded part of your roaster.

User avatar
engineercarl
 
Posts: 56
Joined: Fri Nov 22, 2013 6:47 pm

Re: MAX31855 throwing crazy numbers

Post by engineercarl »

Have you added the suggested 0.01uF capacitor? Check-out page 11 of the datasheet http://www.adafruit.com/datasheets/MAX31855.pdf

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