Driving a Relay through extruder stepper output
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Hi everybody
I need to drive a ON/OFF relay through a extruder stepper output.
The idea is to activate relay when extruder is supposed to extrude, and to Switch OFF relay when extruder is supposed to retract or stopped.
How could I managed this ?
Duet2 Ethernet + Duetx5 / RFF3
Thanks !
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@sylvain do you need to use the actual stepper driver output or just have it correlate to any movement on the E axis? And is it instead of a regular stepper motor, or in addition to the stepper motor.
As far as I can wrap my head around it, neither will work without hacking the firmware, but clarifying the above might help get some relevant pointers on where to go hacking.
edit: simplest approach may be to use an external stepper driver on the CON_LCD and a little bit of external circuitry to buffer and stretch the step pulse so it would hold the relay closed while there is a continuous stream of step pulses. (or tap into the step signal for an existing driver if you need both)
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I do not need a stepper motor to run in the same time.
The idea is that slicer generates E movment and that these E movment activates the relay.
Thanks !
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Then the CONN_LCD header will allow two adittional stepper drivers to be attached, the firmware will generate step pulses in relation to the E movement.
Then you're left with smoothing the pulses so you get a continuous signal when extruding, this could perhaps be as simple as a diode and a capacitor, maybe a resistor to tune the time constant, and an external relay moduel with a built in transistor to drive the coil.
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What is your usage case?
If you're not FDM printing, but instead trying to control an external device via the relay (like say a welder), you could probably set the machine up in laser mode.
See M542
https://duet3d.dozuki.com/Wiki/Gcode#Section_M452_Select_Laser_Printer_Mode
