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Temperature - Bed

Heated bed temperature control settings

temperature, bed, pid, peltier

A heated bed keeps material from cooling and shrinking at the base so that it maintains adhesion, and is a necessity for almost all high-performance materials. Use the settings and tuning parameters that best maintain a stable bed temperature.

Quick Reference

Feature	Flag	Default	Notes
Bed PWM limit	`MAX_BED_POWER`	255	Use 255 only if you accept PWM on the bed.
PID control for bed	`PIDTEMPBED`	(bang‑bang)	Enables PID loop; requires `DEFAULT_BED_(KP\|KI\|KD)`.
Bed hysteresis	`BED_LIMIT_SWITCHING`		Active only when PID is off.
Gradual cooling	`BED_ANNEALING_GCODE`		Adds `M190 R T`.

#define MAX_BED_POWER int

Max duty cycle for the bed (0–255).

When below 255 a PWM divider is applied to the bed driver.
Use only if you are comfortable with PWM on your heater.

#define PIDTEMPBED

Enable PID control for the heated bed.

With PIDTEMPBED defined, a PID loop drives the bed at the same frequency as the extruder PWM.
When disabled, bang‑bang is used; BED_LIMIT_SWITCHING can be enabled to add hysteresis.

#define MIN_BED_POWER int

Minimum power to improve PID stability.

#define PID_BED_DEBUG

Print bed‑PID debug data to the serial port.

#define DEFAULT_BED_KP float

Proportional gain for the bed PID.

#define DEFAULT_BED_KI float

Integral gain for the bed PID.

#define DEFAULT_BED_KD float

Derivative gain for the bed PID.

#define BED_LIMIT_SWITCHING

Keep the bed temperature within BED_HYSTERESIS of the target.

Only relevant when PIDTEMPBED is not defined.
The switch creates a hysteresis band around the set‑point.

#define PELTIER_BED

Enable a Peltier device for the heated bed.

A Peltier module can both heat and cool.
The firmware assumes a simple bang‑bang loop (0/255).
A second GPIO pin controls the current direction (relay or H‑bridge).

#define PELTIER_DIR_PIN int

GPIO pin that drives the relay (or H‑bridge) for direction control.

#define PELTIER_DIR_HEAT_STATE enum

Pin state that activates heating.

#define BED_ANNEALING_GCODE

Add M190 R T to slow down bed cooling.

When defined, the firmware inserts a gradual‑cooling G‑code sequence after M190 R.
Useful for delicate materials that benefit from a slow temperature drop.