When reed switch is opened, pin 2 of Arduino goes high with the help of the pull-up resistor R2, and the alert signal is available through the piezo-speaker PZ1 (not an active piezo-buzzer). At the ...

Something that is missing when they are bought is automatic end-stops, although the ‘Woodpecker’ control board that comes with the machines, which is based on an earlier Arduino shield, has headers ...