The Hall sensor addon allows the automatic homing of the RA ring (once calibrated).
The addon consists of
The sensor is mounted somewhere on the frame and the magnet is mounted on the RA ring.
The absolute position of these items does not matter much, but the magnet should be within 15 degrees of the resting (power off) position of your mount. Ideally, the magnet and sensor are in the same location (triggered) when your mount is powered off. This gives the quickest homing procedure.
This how I installed it on my OAT. I created a holder for the sensor that sits just below the bearing on the right mount.
Then I made a holder for one of the magnets and super glued it to the bottom of the RA ring.
OATControl is the only way to use this add on at the moment. After initiating the homing, OAT works as follows:
Other sensors may work, but currently the firmware expects that the sensor to returns LOW when triggered (within range of magnet). If your sensor behaves differently, please let us know on Discord and we will make it configurable.
You need to run GND and 5V as well as a signal to the sensor. On the MKS V2.1 it is pin 53 (by default) and on the Mega it is pin 40 (by default).
The firmware does not support the homing from the LCD, only OATControl supports this. The Settings dialog is used to both calibrate and use this addon.
To enable this feature in the Firmware make sure the following line is present in your
#define USE_HALL_SENSOR_RA_AUTOHOME 1
If you are not using the standard pins mentioned above, you can also add a line like this:
#define RA_HOMING_SENSOR_PIN 53
This should be supported by the online configuration tool soon.
To calibrate this:
auto-home ra. If all goes well, you will end up with the RA ring such that the magnet is centered on the hall sensor.
set home. This will zero out all the steppers.
set ra home offset.
Voila, calibrated and ready to party.
To use this in a session:
Ready to go.