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RobTillaart / MAX31855_RT

Arduino library for MAX31855 chip for K type thermocouple
MIT License
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Random internal temperature & thermocouple readings #19

Closed z01ne closed 3 years ago

z01ne commented 3 years ago

I tested two modules with 3 boards, I get the same readings: I added 10nF cap between T- and T+, and in one board, I cut the connection between T- and gnd

20:47:19.425 -> Status: STATUS_OK 20:47:19.425 -> RAW: 1100-1000-0100-1100-1000-0100-0101-0000 20:47:19.425 -> Internal: -123.688 20:47:19.425 -> TMP: -891.250 20:47:20.413 -> Status: STATUS_OK 20:47:20.413 -> RAW: 1100-1000-0000-1000-1000-0100-0110-0000 20:47:20.413 -> Internal: -123.625 20:47:20.413 -> TMP: -895.500 20:47:21.405 -> Status: STATUS_OK 20:47:21.405 -> RAW: 1100-0111-1111-0000-1000-0011-1101-0000 20:47:21.405 -> Internal: -124.188 20:47:21.405 -> TMP: -897.000 20:47:22.436 -> Status: STATUS_OK 20:47:22.436 -> RAW: 1100-1000-0000-0100-1000-0011-1111-0000 20:47:22.436 -> Internal: -124.063 20:47:22.436 -> TMP: -895.750 20:47:23.455 -> Status: STATUS_OK 20:47:23.455 -> RAW: 1100-1000-0001-1100-1000-0011-1000-0000 20:47:23.455 -> Internal: -124.500 20:47:23.455 -> TMP: -894.250 20:47:24.435 -> Status: STATUS_OK 20:47:24.435 -> RAW: 1100-1010-1111-1100-1011-0011-0110-0000 20:47:24.435 -> Internal: -76.625 20:47:24.435 -> TMP: -848.250 20:47:25.440 -> Status: STATUS_OK 20:47:25.440 -> RAW: 1100-1011-1111-1000-1100-0011-0001-0000 20:47:25.440 -> Internal: -60.937 20:47:25.440 -> TMP: -832.500 20:47:26.434 -> Status: STATUS_OK 20:47:26.434 -> RAW: 1100-1100-1111-0000-1101-0010-1111-0000 20:47:26.434 -> Internal: -45.062 20:47:26.434 -> TMP: -817.000 20:47:27.432 -> Status: STATUS_OK 20:47:27.432 -> RAW: 1100-1010-1111-1000-1011-0010-1110-0000 20:47:27.432 -> Internal: -77.125 20:47:27.432 -> TMP: -848.500 20:47:28.459 -> Status: STATUS_OK 20:47:28.459 -> RAW: 1100-1011-0010-1000-1011-0010-1110-0000 20:47:28.459 -> Internal: -77.125

Thank you

RobTillaart commented 3 years ago

Strange readings. Not enough information to draw any quick conclusion.

z01ne commented 3 years ago

Can you shed some light on where I should look? Thanks

z01ne commented 3 years ago

It's the same with other libs. I just want to know if possible, does a working chip report correct internal readings without a thermocouple connected? Thanks

RobTillaart commented 3 years ago

Some questions

RobTillaart commented 3 years ago

What are the expected temperatures (approx?)

RobTillaart commented 3 years ago 
                     TEMPERATURE             INTERNAL           STAT
20:47:19.425 -> RAW: 1100-1000-0100-11  00-  1000-0100-0101-   0000
20:47:20.413 -> RAW: 1100-1000-0000-10  00-  1000-0100-0110-   0000
20:47:21.405 -> RAW: 1100-0111-1111-00  00-  1000-0011-1101-   0000
20:47:22.436 -> RAW: 1100-1000-0000-01  00-  1000-0011-1111-   0000
20:47:23.455 -> RAW: 1100-1000-0001-11  00-  1000-0011-1000-   0000
20:47:24.435 -> RAW: 1100-1010-1111-11  00-  1011-0011-0110-   0000
20:47:25.440 -> RAW: 1100-1011-1111-10  00-  1100-0011-0001-   0000
20:47:26.434 -> RAW: 1100-1100-1111-00  00-  1101-0010-1111-   0000
20:47:27.432 -> RAW: 1100-1010-1111-10  00-  1011-0010-1110-   0000
20:47:28.459 -> RAW: 1100-1011-0010-10  00-  1011-0010-1110-   0000

There are some relative big jumps in the bit patterns esp 5 -> 6 jumps of 10/15 degrees which is not expected.

z01ne commented 3 years ago

which version of the library?

Current Master

which boards tested? which pins? hardware SPI or software SPI (did you test both?

-nodeMcu 1.0 ESP 12E (CLK D4 MISO D6 CS D4) -Arduino Yun (ATmega32u4) (CLK 13 MISO 12 CS 7) -STM32f1103c8 BluePill (CLK PA5 MISO PA6 CS PA4) In SW SPI: I tested more PIN configurations, I get "STATUS_OK" with random readings both internal and thermocouple. In Hardware SPI: I can't get it working, I get always "STATUS_NO_COMMUNICATION".

where did you buy the max31855 ?

From Aliexpress two generic boards, a MAX chip with a cap between Vcc and Gnd.

did you check soldering on the board? length of the wires used? do you use pull-ups resistors? if so which value? have you checked power voltage? Stable?

Setup in a breadboard with a level shifter for Arduino Yun For other boards tested with breadboard and directly with jump wire of 12cm I used a 1K and a 2K pull-up resistor

have you checked power voltage? Stable? From USB port, checked with a multimeter, it seems right.

What are the expected temperatures (approx?) Testing in room temperature

I think I close and try to buy it from another source.

Thank you for your insights.

RobTillaart commented 3 years ago

hardware SPI is tested by me on uno, and ESP32 (possibly NANO too), so looks like a different set - although your nodeMCU is that a ESP32?

software SPI should work on any platform in theory ..... (from famous last quotes)

I bought my max31855 from an ADAfruit reseller -

pull up resistors sound OK. Wire length sound OK

Do you have a link to the aliexpress thingie?

z01ne commented 3 years ago

nodeMCU v1.0 is an ESP8266 12E

software SPI should work on any platform in theory ..... (from famous last quotes)

Good to know .

I bought my max31855 from an ADAfruit reseller -

Better than having a headache

Do you have a link to the aliexpress thingie?

https://www.aliexpress.com/item/1005002526054145.html This one have a short between T- and Gnd pin.

https://www.aliexpress.com/item/32306974965.html This one sound ok.

RobTillaart commented 3 years ago

@Z01NE See that you closed the issue, is the cause understood? Can you explain in short here for future reference?

z01ne commented 3 years ago

No, not really I suspect a faulty chip, I'm waiting for another one, I'll let you know when tested.

sergiocntr commented 2 years ago

hello everyone, just to thank Rob for this great library and z01ne for putting me on the right path looking for the problem of my board (same) giving a short to ground error: with a cutter I removed the track near the chip and thing is resolved. Strange I had to add an offset of +10 C.

RobTillaart commented 2 years ago

@sergiocntr You're welcome,

Strange I had to add an offset of +10 C.

Never heard before of such deviation (damage?), fortunately the library does support just offsets 😁

sergiocntr commented 2 years ago

@RobTillaart maybe.... I just need to know a fireplace fumes temperature for now, it does not need to be very precise.( I hope that the difference remains constant as the temperature rises, for now I have checked it with ice) I'll do some tests with a DS18b20 and boiling water. In the lib Error handling was also very useful.👍

RobTillaart commented 2 years ago

What temperature range are you talking about? Fireplaces can be very hot I can imagine,

sergiocntr commented 2 years ago

Seeing the colors on the stainless steel flue (you know that steel colors when exposed to high temperatures) I don't think it goes above 300 degrees Celsius in case it lets go too much. the flame.

RobTillaart commented 2 years ago

Given the range a thermocouple is the way to go.

You might have a look at https://learn.adafruit.com/adafruit-mlx90640-ir-thermal-camera?view=all This part will measure temperatures ranging from -40°C to 300°C with an accuracy of +- 2°C (in the 0-100°C range). With a maximum frame rate of 16 Hz (the theoretical limit is 32Hz but we were not able to practically achieve it), It's perfect for creating your own human detector or mini thermal camera.

sergiocntr commented 2 years ago

Fine! Grazie. 👍

RobTillaart commented 2 years ago

Or - https://learn.adafruit.com/using-melexis-mlx90614-non-contact-sensors