MAX31855 problem - reads zero

[defender146]

I recently bought Thermocouple Amplifier MAX31855 breakout board and i'm having dificulty to get the temperature data.

I did all the steps of wiring and I even put the capacitor.

When I connected the Arduino to the MAX31855 I received the temperature data for a few minutes and then the data became very unstable until stopped sending data. The results are always 0. The thermalcouple i'm using is the same you have in the shop and its not in contact with anything grounded.

Can someone give me a tip to fix this problem?

Thank you

[adafruit_support_mike]

Post a photo of your hardware and connections and we'll take a look.

[mustakis]

i have also same problem with both of codes. i bought this board on christmas, from http://grobotronics.com physical shop. i tried everything i read around the web but same. i test thermocouples with multimeter set to the Ohm’s /Continuity function and looks ok.

IMG_0086.JPG (802.5 KiB) Viewed 791 times

IMG_0083.JPG (1006.49 KiB) Viewed 791 times

IMG_0085.JPG (853.08 KiB) Viewed 789 times

[adafruit_support_rick]

What kind of thermocouple are you using? The MAX31855 does not support grounded thermocouples - if the sensor touches ground the chip will return an error

[mustakis]

What kind of thermocouple are you using? The MAX31855 does not support grounded thermocouples - if the sensor touches ground the chip will return an error

if grounded is the one with metal probe, i don't. i use the two from the 1st screenshot

[adafruit2]

if it starts working...then stops...its likely a power or wiring issue. chips dont tend to 'stop working' for no reason :)

[mustakis]

in my case doesn't stops because never starts. always appear the message as in the photo.

[mustakis]

i had check my wires again and again i tried variations of your example code, as the one paddygoat paste here, but never i get nothing else different than the error. could you give me a guess why?

[adafruit_support_rick]

No idea. Let's try replacing the module. Please email [email protected] with a link to this thread for a replacement

[samhm17]

So I've got a similar MAX31855 problem, I can't seem to read anything other than zeros.
I'm using 4 max31855s to monitor thermocouples inside an oven. I'm currently using picoReflow to control my oven (https://github.com/apollo-ng/picoReflow). It's a really nice interface but only needs one thermocouple to drive the oven and that's all it plots. I'm trying log and plot data out of all 4 thermocouples but I can't seem to get any meaningful data. PicoReflow seems to read an accurate temperature and drive the oven properly but all I can read from the '855s are zeros.

Here's the basis of my logging... still working out matplotlib and live plotting etc.

Any advice would be greatly appreciated, thanks!

Code: Select all

from sys import argv
import RPi.GPIO as GPIO
import datetime
import time
import max31855

now = datetime.datetime.now()
date = now.strftime('%d-%m-%Y')

CLK1 = 22
CLK2 = 12
CLK3 = 24
CLK4 = 9

CS1 = 27
CS2 = 19
CS3 = 20
CS4 = 23

DO1 = 17
DO2 = 16
DO3 = 14
DO4 = 15

temp1 = max31855.MAX31855(CLK1, CS1, DO1, 'c')
temp2 = max31855.MAX31855(CLK2, CS2, DO2, 'c')
temp3 = max31855.MAX31855(CLK3, CS3, DO3, 'c')
temp4 = max31855.MAX31855(CLK4, CS4, DO3, 'c')

prompt = ">  "
print(temp1.get())
print(temp2.get())
print(temp3.get())
print(temp4.get())
print '\n'
print date
print "press ctrl-c to kill"
print "What would you like to call your file?"
file_prompt = raw_input(prompt)

file_name = file_prompt + ".dat"
file = open(file_name,"w")
file.write(date)
timestep = 1
time = 0
start = datetime.datetime.now()

while True:
            now = datetime.datetime.now()
            runtime = now - start
            t1 = temp1.get()
            t2 = temp2.get()
            t3 = temp3.get()
            t4 = temp4.get()

            data_string = str(runtime) + " " + str(t1) + " " + str(t2) + " " + str(t3) + " " + str(t4)
            print data_string
            file.write(data_string)
            time = time + timestep
            sleep(timestep)

[adafruit_support_bill]

@samhm17 - Please post some clear photos showing your soldering and connections to the sensor.

[samhm17]

In popping the '855s off their stickyback mounting system, I've discovered that temp2 seems to have a burnout on the backside of the board. (second board from the left)
I'm using a set of Marlin plugs and sockets to pass the thermocouples through the enclosure. The connections between the '855s and the sockets are done with the correct k-type thermocouple wire... I don't think I have any grounds there in there. A couple of my solderings do look a little dry so I'll tune them up and try again.

Is there anything it would be useful to have a closer look at?

Thanks for the time and thought!

[adafruit_support_bill]

Looks like a scorch mark in the case corresponding to the burn mark on the back of temp2. But there are no traces in that area of the board, so I don't see how it could have originated from on the board itself. Can you post a close-up photo of that?

Does your picoReflow read from one of these sensors, or does it have a MAX31855 of its own?

[samhm17]

So the scorch mark turns out to be a bit of burnt flux that flaked off.

The picoReflow reads from temp1, the second board from the right.

[adafruit_support_bill]

Interesting. So PicoReflow can read from temp1, but your code just returns zeros? And if you connect picoReflow to one of the other boards, can it read that as well?