this repstrap is a bit different: it doesnt use any of the usual reprap electronics or sourcecode on a microcontroller.

the gcode is generated like usual via skeinforge or similar tools but emc2 and some shell and python components take control of parsing it and doing the magic.

the dc-motor as visible in the pictures for the classic darwin-style extruder we currently use is driven by a dc-motor driver based on this:

also in the same box are 2 tip122 transistors which switch gnd for 2 supplies in open collector mode.

the whole thing is deadlocked with and-gates (inline in the 'step' and the pwm lines for the transistors) with the other 4 inputs of the and-gates driven from a 'charge-pump' <add schem>

the chargepump gets a 'rectangular ac signal' on one input. if its missing the output goes low. if it hangs high, the same. see it as an electronic dead-man switch driven by emc2

its based on some caps, diodes, more caps and 2 or 3 transistors. i'll add a schematic soon.

for some pics of our extruder head see blogposts about reprap


configs: (for now, will move that somewhere here)


  • works somehow


  • does one really need/want a 80mm fan to force-cool the object?
  • build stepper-direct-drive and compare it against our geared worm-drive
  • try geared motor as direct drive.
  • fix heater-pid-loop Dgain
  • clean up code
  • Documentation / pictures / howto



Last modified 13 years ago Last modified on Nov 27, 2011, 7:05:30 AM

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