I'd like to have the 12V PID output of an old Printrboard hotend control a relay that attaches to a 120V crockpot for something I'm making. I have everything working fine using a relay, but because the hotend heater is using PID control, the relay clicks about 3 times per second each time it needs to heat up the crockpot.
Not only is this sound annoying, but it will likely reduce the life of the relay significantly. I need the crockpot temperature controlled, so the programmatic thermistor control on an old 3D printer board is a huge help, and probably cheaper than the alternatives. Especially since this board has an SD slot built in and can run any code on power-up. In "bang-bang" control, there would be less clicking as the crockpot heats up, and the relay wouldn't be damaged.
I can't update the firmware on my board to use a different pin because it is a really old Printrbot board. All the required software is almost 5 years old and is really difficult to find. Fortunately the Printrboard does support
M301. So, I should be able to use this command to switch from PID control to bang-bang.
In Marlin's documentation, it describes a command called M301, along with a lot of variables for using this command. The problem is, I don't know what any of these variables mean.
M301 [C<value>] [D<value>] [E<index>] [I<value>] [L<value>] [P<value>]
[C<value>] C term (requires PID_EXTRUSION_SCALING) [D<value>] Derivative value [E<index>] Extruder index to set. Default 0. [I<value>] Integral value [L<value>] Extrusion scaling queue length (requires PID_EXTRUSION_SCALING) [P<value>] Proportional value
About the only thing I know for sure is that the extruder index is 0.
What command would I enter to make this a bang-bang PID controller, so that I don't damage my relay long-term?