CNC plotter 1800 x 80cm, first build, questions and queries.

[Doddy]

Okay, some weirdness now understood with this BoB.

The parallel port, pins 18 through 25 are supposed to all be grounded, at the PC side. A 25-way parallel cable should be expected to be fully wired, pin-1 to pin-1 through pin-25 to pin-25.

The "CNC4PC model C1" pulls the pin 18 high, and monitors this to be dragged low by the insertion of the parallel port cable to the PC. Without this, although the PC and the board supply voltage may be present, the outputs (at least) are inhibited.

Solution - a fully wired 25W parallel cable (and similarly wired parallel port), or short pin 18 to PC ground (pins 19-25).

Pic 1 - board with separate 5V supplies (PC and Main) - and EN set high. Power LEDs for the two supplies on, but the output-enable LED (on, if the main PSU is on, but extinguished with the PC power supply added). Shorting link from a ground to pin-1 to extinguish Output 1 LED (note: they are all off because pin 18 is floating).



Pic 2 - Added a ground to pin 18. Output-Enable LED is illuminated as are all other outputs, except for pin-1 because of the aforementioned shorting link.



All other outputs and inputs tested okay.