Hi,

I made some progress with my build. Machine is alive but lot of work to be done. Anyway, my electronic wiring at the moment is as simple as neccessary for working machine, with E-Stop button implemented only as an input signal for software. I want to make final wiring properly to have a safe machine and environment. I spent few days reading materials and ended up with attached sketch. It is more a logic diagram, definitely not a wiring plan.

I followed basic principles:

  • Mushroom latching style E-Stop button is operated directly on 230V line.
  • Pressing the E-Stop button powers off stepper motors and spindle, leaving the controller powered.
  • Start button (NO) is combined with holding control relay.
  • Stop button (NC) used to power down the system, instead of using E-Stop button.




My idea is to communicate as many emergency situations from hardware level to software as possible. At the sketch bottom there is logical AND block that signals existing emergency situation to software. (Some inputs may need inverting.) I wrote some notes to explain my mind:

  • AA - Control relay (R) function check. (Why not?)
  • BB - Contactor (C) function check. (Why not?)
  • CC - If VFD triggers circuit breaker (CB1), it is emergency situation - steppers must stop or the tool breaks.
  • DD - If stepper motor branch triggers circuit breaker (CB2), spindle should be stopped not to damage the workpiece.
  • EE - If stepper motor driver signals fault, this is emergency. One of indicated faults is stall condition which could damage machine if it happens to dual-motor Y-axis. (Happened to me with my first MDF build.)
  • FF - If the control branch dies (CB3 triggered), software should know it.
  • GG - NO contact of E-stop button to signal manual E-Stop button press.
  • HH - All previous input signals logically multiplied (AND) and sent to software.


Other notes:

  • I want to have more E-Stop buttons available. NC contacts will be wired in series, NO contats in paralel.
  • That AUX blocks beside circuit breakers are auxiliary contacts that monitor breaker status.
  • Meter at the diagram beginning is power meter so I can track power consumption.
  • I do not consider a water pump or dust collector to be emergency hazard thus not present in sketch.
  • VFD is loud and has no on/off button so I will add a switch between contactor (C) and VFD to power it off in case when I want to use router without spindle.


Few questions:

  1. What about fuses between 48VDC power supplies and stepper motor drivers for extra safety? I found here a post explaining why not to do it but I have also seen wirings with fuses included. Which is correct?
  2. I drive the contactor (C) coil directly from 230V line. Would it be better to power it from control relay (R) contacts? They would be in series and contactor would not power up if the relay is broken.
  3. If circuit breaker CB4 triggers, which means there is absolutely no control of system, would it be reasonable to disengage the CB3 branch? Relay in CB4 branch that would control CB3 branch via NO contacts - to act like automated 2nd Stop button.


I would like to ask you to review it and provide me feedback particularly on design flaws. Any tips for improvement are welcome of course.

Thank you.