dc42:
- How do you have the 3 breakout boards wired to the Arduino?
I'm sharing DO and CLK pins across 3 breakout boards
MAX6675 breakout board
D4 // CS for Pre-heater1 temperature
D5 // CS for Post-heater2 temperature
D6 // CS for Pump housing temperature
D7 // DO
D8 // CLK
- What code are you using?
max6675.h library
- Is your thermocouple electrically isolated from the motor housing it is on? If it isn't, then you will pick up ground noise from the motor.
All the breakout boards use the same Vcc and Ground. The thermocouples are measuring water which is pumped by the pump, so it's hard to say to what level they are connected electrically. But I completely removed the pump breakout board and just tried it with the two water temp thermocouples and I still have the same problem. If I hook either one thermocouple up everything is fine. As soon as I have both connected, temperature for both fluctuates in the 30s F.