This is a feature to protect your printer from burn up in flames if it
has a thermistor coming off place (this happened to a friend of mine
recently and motivated me writing this feature).
The issue: If a thermistor come off, it will read a lower temperature
than actual. The system will turn the heater on forever, burning up the
filament and anything
else around.
After the temperature reaches the target for the first time, this
feature will start measuring for how long the current temperature stays
below the target minus _HYSTERESIS (set_temperature -
THERMAL_RUNAWAY_PROTECTION_HYSTERESIS).
If it stays longer than _PERIOD, it means the thermistor temperature
cannot catch up with the target, so something *may be* wrong. Then, to
be on the safe side, the system will he halt.
Bear in mind the count down will just start AFTER the first time the
thermistor temperature is over the target, so you will have no problem
if your extruder heater takes 2 minutes to hit the target on heating.
In some cases the Bed Heater FET heats up more then stepper drivers, so
this change add the bed monitoring to the controller fan. As soon as the
bed heater is turned on, the controller fan will run as well.
Recommended for those who are using the Z Probe for Z Homing (as
Z-Endstop)
This feature has two changes:
1) Allow user to choose where the Z Probe will touch the bed when homing
all axis together (G28) by setting below defines:
Z_SAFE_HOMING_X_POINT
Z_SAFE_HOMING_Y_POINT
2) Prevents the user to perform Z Axis Homing when the Z Probe is
outsite bed.
In previous version, even with PWM = 127, the system turns the FET off
and then on in the next cycle. This bevavior may increase the FET heat
dissipation.
It was fixed keeping the FET always On when PWM=127.
- Added "Z_RAISE_BEFORE_HOMING" for raising Z the defined distance
before homing. This is useful to avoid Z-Probe collision when hotend is
near bed.
- Fixed the issue of Z not going bellow Z_PROBE_OFFSET when
"min_software_endstops" is true.
Now the Z_PROBE_OFFSET is not set in Z_MIN_POS, it is added after
homing.
If "SHOW_TEMP_ADC_VALUES" is defined in Configuration_adv.h, the M105
command will present, after tradicional temperatures, the ADC value read
from temp sensors. This is great for adjusting thermistor tables with
thermocouple.
From Pronterface you can see the ADC value and compare with a
thermocouple reading.. then you just need to create your own thermistor
table.
Since this merge doesnt change the original information, it doesnt mess
with PC software parsing (tested under Pronterface and Repetier-Host).
alexborro