Is there a way that a relay can be triggered only when the stepper driver is moving in a positive direction, ie can I turn on a fan only when the extruder is extruding and turn it off when its retracting?

The M571 command does this (see [reprap.org]), but AFAIK the only firmware that supports it is RepRapFirmware.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

You could tap off the direction pin on the driver board, that might do what you want. You'd have to add a transistor / FET / op-amp or similar power amplifying device though.

Edited 1 time(s). Last edit at 02/19/2016 10:28PM by nebbian.