PT100 Heater Fault



  • I posted this in general because I'm not sure if this is a hardware issue or a software issue, I copied the code from dc42's blog when he build his Kossel so I tend to think it's poor soldering.

    When I plug in either one of my PT100 sensors into the daughterboard, two wire or four wire config (two wire with jumpers from each pin into the middle two terminals (I'm calling them 2 & 3) on RTD1 (or whatever it is) and a jumper wire connecting the outermost (1 & 4 ) together. It looks to me like I follow the 4 wire config exactly how dc42 showed it, but the 2 wire documentation need work.

    I am getting a temperature reading of 2,000°C and I'm not sure how to proceed. I switched back to a generic thermistor because it worked, I would like to solve my problem with the PT100 sensors though.

    What could cause this and how should I avoid the same or similar issue in the future?

    It appears I'm getting continuity from one leg to the end of the same wires with a four wire config so I'm really at a loss as to how to proceed with this.

    Thank you in advance.



  • What have you set in config.g for the pt100?


  • administrators

    @NoSkillzEngineer:

    When I plug in either one of my PT100 sensors into the daughterboard, two wire or four wire config (two wire with jumpers from each pin into the middle two terminals (I'm calling them 2 & 3) on RTD1 (or whatever it is) and a jumper wire connecting the outermost (1 & 4 ) together.

    Jumpering 1 and 4 is not correct. In a two-wire configuration you need to jumper 1 to 2, and 3 to 4. Recent production PT100 boards have 2-pin jumper blocks for doing this.



  • @dc42:

    @NoSkillzEngineer:

    When I plug in either one of my PT100 sensors into the daughterboard, two wire or four wire config (two wire with jumpers from each pin into the middle two terminals (I'm calling them 2 & 3) on RTD1 (or whatever it is) and a jumper wire connecting the outermost (1 & 4 ) together.

    Jumpering 1 and 4 is not correct. In a two-wire configuration you need to jumper 1 to 2, and 3 to 4. Recent production PT100 boards have 2-pin jumper blocks for doing this.

    Ohhhh…..Ha! Uhhhh whoops. I thought I tried that though? Yeah I saw that in the newer documentation of the daughterboard, was the area by the solder pads changes for the jumpers or were the jumpers just soldered on? It looked like the area was changed to fit the jumpers. I've thought about just buying a new daughterboard.

    I'll try doing this correctly, so just to be clear, jump 1 to 2 & 3 to 4 and put the main two wires in 2 & 3? The main two wires go in what terminals? (Assuming from left to right with the terminals facing me).



  • @DjDemonD:

    What have you set in config.g for the pt100?

    As of right now since I am not using it, it is commented out. This is how it reads though, taken right from dc42's blog (unless I misunderstood, I have used a PT100 sensor before the last time round in a 4 wire config…I thought I knew how to do this! Guess not).

    This is the whole heater section of my config

    ; Heaters
    M301 H0 S1.00 P10 I0.1 D200 T0.4 W180 B30 ; Use PID on bed heater (may require further tuning)
    M305 P0 T100000 B3950 C0 R4700 ; Set thermistor + ADC parameters for heater 0
    M143 H0 S80 ; Set temperature limit for heater 0 to 80C
    ;M305 P1 X200
    M305 P1 T100000 B3950 C0 R4700
    ;M305 P1 T100000 B4725 C7.060000e-8 R4700 ; Set thermistor + ADC parameters for heater 1
    M143 H1 S280 ; Set temperature limit for heater 1 to 280C

    ;M305 P1 X200 should be the PT100 sensor.

    Then I bumped "M143 H1 S280" to "S380"

    For the record, when I tried hooking it up, all I did was comment out the M305 just under it and changed S280 and S380 and nothing else.


  • administrators

    @NoSkillzEngineer:

    I'll try doing this correctly, so just to be clear, jump 1 to 2 & 3 to 4 and put the main two wires in 2 & 3? The main two wires go in what terminals? (Assuming from left to right with the terminals facing me).

    That's correct.



  • @dc42:

    @NoSkillzEngineer:

    I'll try doing this correctly, so just to be clear, jump 1 to 2 & 3 to 4 and put the main two wires in 2 & 3? The main two wires go in what terminals? (Assuming from left to right with the terminals facing me).

    That's correct.

    Okay, thank you. I'll try it this weekend.


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