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IndustryArena Forum > CNC Electronics > CNC Machine Related Electronics > Any errors or concerns with my planned controller wiring?
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  1. #1
    Join Date
    Jun 2021
    Posts
    105

    Any errors or concerns with my planned controller wiring?

    My previous posts have received many views but no feedback to date, perhaps in part to their length. Understanding that my last posts required a great deal of time to digest, I thought I would try one last time to get forum feedback on the power wiring for my controller enclosure. It is hand drawn, and uses words instead of electrical symbols, but my hope is that those with experience will catch any glaring errors - I really do not want to compromise my Masso, MX4660 driver, ... or my home.

    A few quick notes:
    Some 3D printed parts are temporarily mounting certain components (Estop, AC power module) close to their eventual location in the enclosure
    I have a power module which fuses both Line and Neutral, currently with 10A (came with unit), and it also serves as an on/off switch and EMF filter

    I have 5, 12, 2X24, and 48VDC power supplies, dedicating 24VDC to the Masso and 48VDC to the MX4660 driver. The other VDC will give options for adding sensors, relays...

    I have the grounds and common(-) all terminating in their own connected terminal blocks.

    I have the Masso POS+ on a 1A fuse, and the other 24VDC also, for now fused the same but the amperage could change depending on future loads

    I have both the POS- and Common(-) of the 48VDC PSU fused, at the moment with 15A fuses, as well as a 63V/2200uF capacitor to help dissipate back EMF

    I have several terminal blocks joined using jumpers, which can be seen in the drawing as small horizontal rectangles across the terminal blocks.

    I understand the time commitment required to provide feedback, but it would very much give me greater peace of mind to actually turn on the power and run my Masso for the first time.

    Thank you

  2. #2
    Join Date
    Nov 2012
    Posts
    1267

    Re: Any errors or concerns with my planned controller wiring?

    One thing I noticed is way too many power supplies. You really need just two: one 48VDC for the driver and one 24VDC for everything else.

    24VDC is the most common control voltage. You will have no problems finding any sensors, buttons, lights, relays, contactors or any other components powered by 24VDC. And you don't want any 5V logic in your machine anyway; you are building a real thing, not an Arduino.

  3. #3
    Join Date
    Nov 2012
    Posts
    1267

    Re: Any errors or concerns with my planned controller wiring?

    Another thing: it is not really necessary to fuse the common (black) wire of the power supply. In fact, it may cause problems. If the black fuse opens and the red one stays closed, the 48VDC current will [try to] flow through the logic common wire.

  4. #4
    Join Date
    Jun 2021
    Posts
    105

    Re: Any errors or concerns with my planned controller wiring?

    Thank you very much for taking the time to provide feedback - I very much appreciate it.

    I understand you comment re power supply number. I had the dual voltage PSU from another project, and had added it just to future proof as I have not yet sourced my other components - that will be the next stage. I figured it would at least secure the space in my panel, and eliminate the need for something like a buck converter should lower VDC be needed. I hope to eliminate it by choosing 24VDC components, which as you mentioned, are readily available.

    With respect to the fusing of common, I no longer can find the links, but I had read some say that it is good practice to fuse the common in floating VDC circuits. If I recall there were a variety of reasons - some related to troubleshooting which may not be so critical in my rather basic application. Since the whole idea was for it to keep my circuits/components safer, I can eliminate it if you feel it is actually adding potential dangers.

    I have also been reading recommendations of using what I think is often called a 'bleed resistor' across the capacitor to have it discharge more quickly. If you have any thoughts on this for my set up, or could suggest a reference to help me determine if I need one and more importantly its size, I would appreciate it. If helpful, my motors are 4 NEMA 23 stepper motors – 3.15V, 4.2 Amps, 0.75 Ohms, 3.0 mH.

  5. #5

    Re: Any errors or concerns with my planned controller wiring?

    Greetings,

    You might not want a fuse in the AC line neutral, if a neutral fuse blows you end up with a dead unit that has line voltage still hot with respect to ground. The only reason to fuse a neutral line is if polarity reversal is possible (old style non polarized plug). We used to call this "hot chassis" in the old days of two prong non polarized ac plugs. Many years since this has been much of an issue. Fused neutral is prohibited by most (all?) codes for building wiring and permanently connected equipment.

    Cheers,
    Stan

  6. #6
    Join Date
    Jun 2021
    Posts
    105

    Re: Any errors or concerns with my planned controller wiring?

    Thank you for the insight. I have found an alternative module from another manufacturer that has one fuse for line only, and will order it soon. After looking in to this further, I found some simple circuits that are used for live line indicators, which I could make, and add using a LED indicator on the front panel door. This would be an additional but interesting project. It is probably easier however to just replace it. In the interim, knowing the potential danger for a live line (with blown neutral fuse), as long as I always unplug the power cord and check both fuses in case of power loss I would be safe - is that correct?

    I appreciate the time you are taking to help.

  7. #7

    Re: Any errors or concerns with my planned controller wiring?

    If you are changing the input module using one with a circuit breaker rather than a fuse might be a good option. I tend to unplug (or flip the breaker on hardwired equipment) whenever I pull covers, just to avoid that awkward bang and flash if I fumble a cover panel or drop some other conductive item. Once I've had a look for any obvious problems and sniffed a bit for burned stuff smells I'll plug it up or flip the breaker on and start probing around with DVM or scope as seems appropriate. Modern wiring devices make shorts far less likely, this habit was developed in earlier times where lots of terminals were pretty shiny exposed metal rather than a screw head down in an insulated tube:-)

  8. #8
    Join Date
    Jun 2021
    Posts
    105

    Re: Any errors or concerns with my planned controller wiring?

    Thank you, it is nice to get perspectives from someone with experience. I wanted to make my finished enclosure fully plug n play, and have planned to have all connections on panel connectors - such as DB9 for my stepper motors, and GX16 for my sensors/probes/etc. This is one reason I wanted to use the power module as the power cord just unplugs. For now, would unplugging serve a similar purpose for disconnecting mains power while I work inside the panel? (I know it does not do the actual job of the breaker). Is that what you meant when you said "I tend to unplug (or flip the breaker on hardwired equipment) whenever I pull covers,..."?Bringing up an old question - should just line (hot) get the breaker?

    Appreciating your continued interest and support in my project.

  9. #9

    Re: Any errors or concerns with my planned controller wiring?

    Unplugging will remove the input AC power. The breaker or fuse should only be on the hot lead. The only difference between unplugging and opening a breaker is that when unplugged ground, neutral, and line are all disconnected. When power is removed by turning off a breaker the neutral and ground connections remain. This is based on the AC input being the sole source of power, which is correct based on your diagram.

  10. #10
    Join Date
    Jun 2021
    Posts
    105

    Re: Any errors or concerns with my planned controller wiring?

    Thank you, you have given a few things to think about and I appreciate your insights.
    Tom

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