Emergency stop cable color
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  1. #1
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    Default Emergency stop cable color

    I've started designing my projects more modular so that machines are more of a work cell than an actual discrete machine. However I do not trust the serial interfaces to handle anything safety related.

    So I've come up with a system of TRS jacks wired so the contacts plugged into them are all in series, and the outputs are all in parallel (but diode or relay isolated). So I can unplug a dummy jack from the safety plugboard and connect in a e stop witch or a limit switch or whatever as I see fit.

    Is there a standard cable color for this? I know yellow/red is the recommended color scheme but I can't get any yellow/red cable cheaply. I thought about solid yellow but that's used for systems that stay live when machinery is in emergency stop. Red seems like the next obvious choice. Is it reserved for anything? This isn't a code application but I try to match up to whatever standards I can.

    Also, there is another soft safety that works in the same way, but only trips into E-stop if activated while a work cycles is active. This is mostly for work gates and locking out anything without a hard reboot sequence. What color should these be?

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    Be aware that TRS jacks often short pins out when partially inserted, defeating your safety - this might not be the best choice. Most safety standards also require dual redundant safety circuits, plus some sensors also require 24VDC, so you end up needing six cores (or more if you want NO contacts).

    I can't speak for the US but in Euroland, orange is used for wiring (usually inside the control cabinet) that stays live with the main disconnect off - usually a cabinet light and laptop socket, plus interconnects between machines. Machine safety wiring doesn't have to be a specific colour and is usually the same as any other ELV controls. There is also no specific colour for equipment that remains live with the e-stop hit; the e-stop is a mechanical movement safety, not electrical. Contactors are not rated for electrical isolation and VFDs with STO certainly aren't.

    Be aware also that safety circuits generally need to not be easily bypassable, except with a key. Magnet switches usually use a special arrangement of various polarities so you can't just grab one magnet and stick it on the sensor, and some are even switching to RFID coded 'magnets' so you can't even grab a new one out of spares. Being able to simply plug in a dummy jack is simply not going to fly with any regulators.

    If this is simply a DIY project... no-one but you is going to care what colour it is.

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    Quote Originally Posted by SomeoneSomewhere View Post
    Be aware that TRS jacks often short pins out when partially inserted, defeating your safety - this might not be the best choice. Most safety standards also require dual redundant safety circuits, plus some sensors also require 24VDC, so you end up needing six cores (or more if you want NO contacts).

    I can't speak for the US but in Euroland, orange is used for wiring (usually inside the control cabinet) that stays live with the main disconnect off - usually a cabinet light and laptop socket, plus interconnects between machines. Machine safety wiring doesn't have to be a specific colour and is usually the same as any other ELV controls. There is also no specific colour for equipment that remains live with the e-stop hit; the e-stop is a mechanical movement safety, not electrical. Contactors are not rated for electrical isolation and VFDs with STO certainly aren't.

    Be aware also that safety circuits generally need to not be easily bypassable, except with a key. Magnet switches usually use a special arrangement of various polarities so you can't just grab one magnet and stick it on the sensor, and some are even switching to RFID coded 'magnets' so you can't even grab a new one out of spares. Being able to simply plug in a dummy jack is simply not going to fly with any regulators.

    If this is simply a DIY project... no-one but you is going to care what colour it is.
    This is just to let me operate otherwise sketchy stuff safely whether I make an error or not. It won't prevent stupidity of malice.

    In this case I'm only going with a single conductor path, because I can wire two switch contacts in series and get the same redundancy. Also, anything very critical will have redundant switches or sensors. I do plan on dual relays on the safety control panel. Also, 24V is readily available over the RS422 connectors, so I'll just run a special wire in the cases that require it. Any E-stop configurable sensor would probably want to output serial data anyway.

    Yeah, I mixed up the mains disconnect and emergency stop discrepency. But these particular systems all have dual input breakers so controls can be powered on and configured (and allow work on the equipment) without worrying about anything starting.

    I'll just use red and be done with it. Purple is reserved for device serial data in this setup and I think I'll go with pink for interlocks. I'll use yellow jacketed cable for non switched mains level outputs, and regular black cords for mains inputs. 24V DC supply will be blue. As will all regular ethernet cables because that's just the most common color for network connectivity.

    The main project that got me thinking about getting this all set up is a configurable ultrahard anodizing system, which involves upwards of 15kV in a water bath, along with timed robotic components shuttling things in and out of various baths.

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    My understanding is that the main reason for the dual path is so that a short in the cable (e.g. it getting cut with all conductors bridged) trips the safety, rather than it disabling the safety. You've still got that issue with partially-inserted TRS jacks shorting out. An RJ11 or similar might be a better choice.

    Things like beam or curtain sensors or the fancier multipole tamper-resistant reed switches need 24V.

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    blue wires for 24vdc

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    TRS jacks are not listed for any kind of load or voltage that makes them useful for this, they are for audio equipment only.

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    Quote Originally Posted by Jraef View Post
    TRS jacks are not listed for any kind of load or voltage that makes them useful for this, they are for audio equipment only.
    I expect 24V at under 1 amp per jack. I could use a 6P6C jack as recommended above. TRS just seemed convenient.

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    Suggest rj45.

    Tools and connectors common so quality is cheap.

    You have 8 conductors.

    There are coonstandard interfaces for different signal formats so spend a few minutes to get those so you can make yours different.


    As long as each end is wired same then CAT5 network cables are cheap and common and in any color or build your own.
    One amp? Most relay could are milli-amps so these would work.

    You can design such that lower level signals are in these cables with conversion interfaces at each end in the equipment.

    Design as closed loop, meaning cable must be in place to be happy.

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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    Quote Originally Posted by Strostkovy View Post
    This is just to let me operate otherwise sketchy stuff safely whether I make an error or not. It won't prevent stupidity of malice.

    Neither will Semtex. But at least you don't get a lot of repeat offenders.

    Are you perhaps over-thinking this to the point of making a problem out of a solution?

    NASA did formal studies ages ago.

    Calculated "MTBF" gets shorter for every CONNECTION added to a system. The more complex, the sooner something fails. Because there are more 'somethings' TO fail.

    They built those calculations from real-world "actual" experience.

    Simpler is safer, IOW.

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    Quote Originally Posted by Tony Quiring View Post
    Suggest rj45.

    Tools and connectors common so quality is cheap.

    You have 8 conductors.

    There are coonstandard interfaces for different signal formats so spend a few minutes to get those so you can make yours different.


    As long as each end is wired same then CAT5 network cables are cheap and common and in any color or build your own.
    One amp? Most relay could are milli-amps so these would work.

    You can design such that lower level signals are in these cables with conversion interfaces at each end in the equipment.

    Design as closed loop, meaning cable must be in place to be happy.

    Sent from my SAMSUNG-SM-G930A using Tapatalk
    I'm already using RJ45 for the serial connections so I'd prefer to use something not interchangeable. Plus there is also ethernet connections mixed in there, unfortunately.

    The safety related stuff is separate from the serial communications so I can make a reliable, robust e-stop ciruit that will not be affected by changing serial configurations, which will be a common occurance.

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    Quote Originally Posted by thermite View Post
    Neither will Semtex. But at least you don't get a lot of repeat offenders.

    Are you perhaps over-thinking this to the point of making a problem out of a solution?

    NASA did formal studies ages ago.

    Calculated "MTBF" gets shorter for every CONNECTION added to a system. The more complex, the sooner something fails. Because there are more 'somethings' TO fail.

    They built those calculations from real-world "actual" experience.

    Simpler is safer, IOW.
    The key to this system, and why I'm putting so much thought into it, is that it's going to be my standard for making equipment that can interconnect. Everything is a connector at each device, and an uninterrupted cable between the two. Cables can and do fail, so I like having connectors on both sides as well having the freedom to use whatever length cable I desire.

    I don't think I'll get higher reliability by frequently soldering an desoldering connections. Also, the serial interface and safety controller all have very clear diagnostic indicators and outputs such that any fault in any cable is traceable to the exact cable without question.

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    Quote Originally Posted by Strostkovy View Post
    The key to this system, and why I'm putting so much thought into it, is that it's going to be my standard for making equipment that can interconnect. Everything is a connector at each device, and an uninterrupted cable between the two. Cables can and do fail, so I like having connectors on both sides as well having the freedom to use whatever length cable I desire.

    I don't think I'll get higher reliability by frequently soldering an desoldering connections. Also, the serial interface and safety controller all have very clear diagnostic indicators and outputs such that any fault in any cable is traceable to the exact cable without question.
    What can I say to disagree ... off the back of a Cable & Wireless pension?

    "Connectors? Lemme tell yah about CONNECTORS!"


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    Quote Originally Posted by Strostkovy View Post
    I know yellow/red is the recommended color scheme but I can't get any yellow/red cable cheaply. I thought about solid yellow but that's used for systems that stay live when machinery is in emergency stop. Red seems like the next obvious choice. Is it reserved for anything? This isn't a code application but I try to match up to whatever standards I can.

    Also, there is another soft safety that works in the same way, but only trips into E-stop if activated while a work cycles is active. This is mostly for work gates and locking out anything without a hard reboot sequence. What color should these be?
    If affordability is an issue with the color you want then you can use solid white and wrap yellow or red tape at each end of the cable. Otherwise find a cable with
    different colored wires and strip out the color you want. Red is what I would use. Or maybe white with red tape at each end.

    If you go to Excess Solutions in San Jose there are numerous spools of wire. They bought the HSC Electronics inventory in 2019. The difference is that at HSC you
    could buy any length you want. This guy at Excess will only sell you a whole spool, no cuts allowed.

    Maybe you will like this better:

    Buy whatever color in heat shrink tubing. Cover each end of your wire run with 6" or more with red shrink tubing. I think it would be better than tape.

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    Cat6 patch leads are dirt cheap, any colour, any length, come preterminated with a fairly solid connector, and have plenty of cores.

    Phone leads are also fairly available albeit slightly less so and with more difficulty in the odd lengths and colours.

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    Quote Originally Posted by SomeoneSomewhere View Post
    Cat6 patch leads are dirt cheap, any colour, any length, come preterminated with a fairly solid connector, and have plenty of cores.

    Phone leads are also fairly available albeit slightly less so and with more difficulty in the odd lengths and colours.
    I am using Cat6 cables for serial communication in the same machinery. I might go with 4C6P connectors like a phone line. Easy to crimp, and I think incompatible.

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    Quote Originally Posted by Strostkovy View Post
    I am using Cat6 cables for serial communication in the same machinery. I might go with 4C6P connectors like a phone line. Easy to crimp, and I think incompatible.
    What I don't like about those connectors are the spring tab that eventually breaks off after so many operations. Or are there more durable connectors.

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    Quote Originally Posted by Jraef View Post
    TRS jacks are not listed for any kind of load or voltage that makes them useful for this, they are for audio equipment only.
    They actually are rated for useful voltage and current, for instance Switchcraft Hi-D series 1/4" jacks:
    Contact Rating: 0.25, 48 VDC make and break, 3A carry only

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    Doesn't solve the issue that by design they short contacts during insertion and removal or if left partially inserted. Seems like a major issue for a safety circuit relying on the contacts not being shorted.

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    Quote Originally Posted by SomeoneSomewhere View Post
    Doesn't solve the issue that by design they short contacts during insertion and removal or if left partially inserted. Seems like a major issue for a safety circuit relying on the contacts not being shorted.
    The back most ring doesn't short.

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    Quote Originally Posted by SomeoneSomewhere View Post
    Doesn't solve the issue that by design they short contacts during insertion and removal or if left partially inserted. Seems like a major issue for a safety circuit relying on the contacts not being shorted.
    I never said it did.


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