Hello Team,
I designed a custom PCB to interface with four thermocouple sensors. The schematic I used is based on Adafruit's MAX31855, and I’m using a Teensy 4.0 microcontroller to read the data from the sensors.
However, my serial monitor is showing the following error messages:
Internal Temp = -0.06
Thermocouple fault(s) detected!
FAULT: Thermocouple is open - no connections.
FAULT: Thermocouple is short-circuited to GND.
FAULT: Thermocouple is short-circuited to VCC.
I’ve tried replacing the thermocouple sensors, but the issue persists. I measured the voltages across the pins, and the following readings were observed:
CS pin: 3.3V
SCK pin: 0.56V
MISO pin: 4.01V
Supply voltage: 3.3V
I'm particularly puzzled by the MISO pin outputting 4.01V, even though the supply voltage is 3.3V. I would expect the MISO voltage to be around 3.3V.
Has anyone encountered a similar issue or have advice on what might be wrong? Any help would be greatly appreciated!
max31855
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
- T_Mo
- Posts: 1423
- Joined: Thu Mar 15, 2018 7:10 pm
Re: max31855
(Community member)
No direct experience with that.
Just for additional info, what supply voltage are you running to the Teensy?
No direct experience with that.
Just for additional info, what supply voltage are you running to the Teensy?
- Elsa_FrozenFever
- Posts: 18
- Joined: Thu Jul 18, 2019 5:06 am
Re: max31855
The teensy is powered by 12V, but the MAX31855 is powered by separate 3.3V supply
- T_Mo
- Posts: 1423
- Joined: Thu Mar 15, 2018 7:10 pm
Re: max31855
Are you using this?
https://www.adafruit.com/product/4323
If yes, then its max input voltage is 5V, via USB or the VIN pin.
Internally it runs from 3.3V via a regulator. So there should be nothing that would explain the 4V you see on MISO.
https://www.adafruit.com/product/4323
If yes, then its max input voltage is 5V, via USB or the VIN pin.
Internally it runs from 3.3V via a regulator. So there should be nothing that would explain the 4V you see on MISO.
- Elsa_FrozenFever
- Posts: 18
- Joined: Thu Jul 18, 2019 5:06 am
Re: max31855
ok, then you mean to say the voltage levels are correct??
I'm wondering then why I'm not able to read the sensor values
I'm wondering then why I'm not able to read the sensor values
- T_Mo
- Posts: 1423
- Joined: Thu Mar 15, 2018 7:10 pm
Re: max31855
No, quite the contrary. If you connected the Teensy or the sensor to 12VDC, then it could have been damaged.then you mean to say the voltage levels are correct??
Please be positive and constructive with your questions and comments.