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Configuration WebUI Documentation

Bryan Mayland edited this page Dec 23, 2020 · 9 revisions

PID Output Parameters

PID Constant Settings

See the PID Controller Theory wiki page for definitions of the PID constants

Blower Output Settings

  • Output Mode Pulse / Voltage (v11 and above) - Pulse mode uses a continuous series of low speed (490Hz) 12V power pulses to regulate the blower speed. Voltage mode is available on HeaterMeter v4.2 hardware and enables step-down circuitry to produce a constant voltage on the output pin between 5V and 12.1V. Voltage mode is more precise with a linear output curve, and runs the blower more quietly than pulse mode.


Attempting to use voltage mode on hardware without support for it will result in the blower turning on and off randomly! Also beware of using voltage mode in combination with a min blower speed which is below the operating voltage of your blower.

  • on above - Do not run the blower at or below this PID output. The blower output is linearly increased from this value to 100%, where the blower output will be MAX. Setting to 50% means that the fan won't turn on until the PID output is above 50%. To replicate the old "only on at MAX" setting, set "on above" to 99%. (LinkMeter v13)
  • min - Minimum blower speed. If the desired PID output is below this, the output will be pulsed between OFF and MIN proportional to the desired speed over a 10 second period.
  • max - Maximum blower speed. The PID output is scaled between 0 and MAX. For example, if the PID output is 100% and the MAX is set to 50, the blower output is 50%. The scaling is computed before comparing with MIN. That is, 10% MIN is always 10% blower speed and not affected by changing MAX.
  • startup max (v12+) - The time between changing the temperature and the first time the temperature is reached, HeaterMeter is in "startup mode". Startup max is the maximum blower speed until the first time the temperature is reached, and overrides the max setting while in startup mode. This allows for accelerated startup by providing more air to the pit or dampening it to prevent overshoot on startup (although editing Kd could be a better solution there).
  • Invert output - Set the blower to be 100% output at 0% PID output and vice-versa. Use if using the HeaterMeter in a cooling mode rather than a heating mode.
  • On at max only - Only use the blower when PID output is 100% (at which point the blower output will be set to MAX). (removed in LinkMeter v13)

Servo Output Settings

  • Pulse Duration - Two values to represent the microseconds for the duration of the servo output pulse. The servo output is scaled linearly between these values based on the PID output percentage. Reducing or increasing the number will adjust how much the servo rotates in that direction before it stops. If a value is entered that is beyond the range of the servo movement, the servo may be damaged especially if left continuously running in this condition. See also Servo Mode
  • Invert output - Set the servo output to 100% open at 0% PID output and close the damper as the PID output increases. To swap the left and right endstops so the servo operates in the opposite direction but is still fully closed at 0% PID output, swap the two servo pulse duration. (There is a bug in AVR firmware before 20200209 which prevents swapping the two duration, if on older firmware, use the Invert Output checkbox)
  • Full open/close only - Only operate the servo in two positions, fully closed (at 0% PID output) and fully open (at any PID output >0%) (removed in LinkMeter v13, use "fully open at")
  • Fully open at (v13+) - Instead of running the servo at 100% PID = 100% servo, you can set the PID output at which the servo should be fully open. 0% PID is always fully closed, this only adjusts the top end. Setting to 1% sets the servo to fully open/close only.
  • A/C input line noise filter - Enables a software filter that can remove much of the noise coming from the mains power supply. Select the appropriate frequency for your country-- 50Hz most of the world, 60Hz in the Americas and some parts of Asia. Mains noise is recognizable in the noise graph as a sine wave with a 20ms (50Hz) or 16ms (60Hz) period.
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