Results 1 to 4 of 4

Thread: Pit alarm threshold as a % or offset of current setpoint

  1. #1
    TVWBB Guru Steve_M's Avatar
    Join Date
    Jul 2013
    Location
    Toronto
    Posts
    2,027

    Pit alarm threshold as a % or offset of current setpoint

    I generally set my pit high/low alarm threshold to +/- 25 degrees from the current set point to let me know if temps are running away or if I've run out of fuel. Of course, this requires you to change the alarm thresholds every time you change the set point.

    What would be nice is a dynamic value based on a % of the current set point, or a numerical offset that is always tracking the current set point.

  2. #2
    TVWBB Super Fan
    Join Date
    Jun 2016
    Location
    Southeastern MN
    Posts
    324
    THAT is once heckuva good idea. Me likey.

  3. #3
    TVWBB Honor Circle Bryan Mayland's Avatar
    Join Date
    Apr 2010
    Location
    Tampa, FL
    Posts
    4,575
    Yeah that's a pretty good idea.

    Thinking it through as I type here, I think it would just be a modifier to the pit probe, a line underneath that allows the alarm value to auto-track the setpoint by a fixed value or percent. Then you'd probably want different percents for the high and low values, because you don't want it to alarm if it is about to go into lid mode? Also what happens if you're using not-the-first-probe as the control probe (pit probe disabled)? You'd probably want that modifier to apply to the control probe and not probe0. Then what if you set up your alarm values and set a setpoint but THEN disabled or enabled probe0, the alarm limits would be set on the wrong probe. Well that means they should probably be stored as the actual alarm values instead of as an additional modifier to just the pit probe which means the current storage isn't going to be able to hold it. So does that mean we start storing all alarm values as positive values and try to use 3 of the 16 bits as a bitfield, 1 bit for enabled, 1 bit for fixed offset, 1 bit for percentage offset, then the remaining bits for the value? That seems a bit hacky, but adding new probe parameters requires a new EEPROM layout and upgrade procedure.

    Oh boy. This is why so little gets done in the codebase, because I start to think about all the possibilities and it becomes so complex that I never get it done.
    I'm that HeaterMeter guy what ruins everybody's free time.

  4. #4
    TVWBB Guru Steve_M's Avatar
    Join Date
    Jul 2013
    Location
    Toronto
    Posts
    2,027
    I’m assuming the pit/control probe value is already being stored? Can the lid open alarm not take precedent over firing a probe low temp alarm? This should take care of those false positives.

    I think storing the actual high/low values makes sense. Those values would get updated every time the set point changes, pit/control probe changes, or the fixed offset or % value changes.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •