Demonstrate Danger, Safely

Dan Maloney and I were talking about the chess robot arm that broke a child’s finger during the podcast, and it turns out that we both have extreme respect for robot arms in particular. Dan had a story of a broken encoder wheel that lead to out-of-control behavior that almost hit him, and I won’t even get within striking distance of the things unless I know they’re powered off after seeing what programming errors in a perfectly functioning machine can do to two-by-fours.

This made me think of all the dangerous things I’ve done, but moreover about all the intensely simple precautions you can to render them non-risky, and I think that’s extremely important to talk about. Tops of my list are the aforementioned industrial robot arm and high powered lasers.

Staying safe with an industrial robot arm is as easy as staying out of reach when it’s powered. Our procedure was to draw a line on the floor that traced the arm’s maximum radius, and you stay always outside that line when the light is on. It’s not foolproof, because you could hand the ’bot a golf club or something, but it’s a good minimum precaution. And when you need to get within the line, which you do, you power the thing down. There’s a good reason that many industrial robots live in cages with interlocks on the doors.

Laser safety is similar. You need to know where the beam is going, make sure it’s adequately terminated, and never take one in the eye. This can be as simple as putting the device in a box: laser stays in box, nobody goes blind. If you need to see inside, a webcam is marvelous. But sometimes you need to focus or align the laser, and then you put on the laser safety glasses and think really hard about where the beam is going. And then you close the box again when you’re done.

None of these safety measures are particularly challenging to implement, or conceptually hard: draw a line on the floor, put it in a box. There were a recent series of videos on making Lichtenberg figures safely, and as a general rule with high voltage projects, a great precaution is a two-button deadman’s switch box. This at least ensures that both of your hands are nowhere near the high voltage when it goes on, at the cost of two switches.

If all of the safety precautions are simple once you’ve heard them, they were nothing I would have come up with myself. I learned them all from other hackers. Same goes with the table saw in my workshop, or driving a car even. But since the more hackery endeavors are less common, the “common-sense” safety precautions in oddball fields are simply less commonly known. It’s our jobs as the folks who do know the secrets of safety to share them with others. When you do something dangerous, show off your safety hacks!

67 thoughts on “Demonstrate Danger, Safely

  1. Glad to see safety being discussed in a sensible and practical way, rather than all the paperwork based, but useless in practice at actually preventing harm, bureaucratic bullsh*t which has invaded government and business.

    1. Yeah we put trivial to bypass/ignore safety lines and locks on. That are usually really annoying to work with, so legally its not our fault.

      Rather than spending 4 mins to educate the new hires that this box is actually dangerous but can be used safely this way. Though in fairness the legal profession and sue everyone culture is somewhat to blame – train somebody and they do something stupid they KNOW isn’t safe and do get hurt, somehow its all the building/employer’s fault for it being possible to do something stupid…

    2. The “paperwork bullshit” is typically just common sense safety, documented. It’s just more ‘cool’ to declare Reading Is For Chumps, Safety Is For Wimps than to engage brain for 30 seconds in order to actually read what it says not what you /think/ it says.

    1. And greatly reduce the efficiency, but yeah in this case it was the clear call.

      On the other hand, finger locks are on my special short list of “things banned even from the UFC”. It probably takes an almost negligible amount of torque to do harm, especially with a seven year old.

    2. Maybe, but not necessarily. How would these limits be implemented? In hardware or software? If hardware, what if someone sets the limits incorrectly? If software, what happens if there’s a bug that the “limit” factor winds up being off by 100x the correct answer? :-)

      In my experience, relying on safety mechanisms that SEEM safe, but really aren’t, is a time bomb waiting to go off – it’s only a matter of time. :-(

    3. The collaborative robots I use calculate the torque required for the given payload along the trajectory and will fault if the required tracking torque deviates beyond the threshold. They also do rebound maneuvers if they detect a collision in that manner.

      The point I’m making here is if they used the robots I use them the kid would’ve been surprised but not hurt, and he would’ve won the game because I’m truly terrible at chess and there’s no way I could come up with a decent chess algorithm.

    4. A big red ABORT switch that stops movement after reversing the last few moves to the initial position UNLESS there was a position sensor failure would be a common sense addition. In the latter case, the arm would just be stopped.

  2. Talking about robot safety in this instance is basically victim blaming – saying the kids should have known how to play chess with an industrial machine.

    Did it never occur to anyone not to put high powered robots in a room with a bunch of kids? Someone needs to lose their job. Especially since solutions are so simple – anything from soft rubber grippers (at the least) to non industrial (3D printed) robot arms of which I’ve seen dozens here.

    Also, sensors. The one thing everyone here at HaD is incredibly good at is attaching sensors to processors. I can think of at half a dozen that could work for this situation.

    1. Yes, the robotic arm weren’t particularly fit for the application.

      At the very least it should have a suitably torque limited grip and feedback for how large of an object it has gripped. If too big, then something else beyond the chess piece itself is in the grip, therefore it should release.

      Limiting overall movement speed is also often a wise consideration around humans. But even here feedback is nice to have. If the power needed to move suddenly increases beyond expectations, then one has hit something and it is therefore wise to stop. (and even a lot of industrial robots do this. But this is more to protect the machine itself, since the speed of movement is often sufficient to be dangerous, especially when accounting for the time it takes the machine to stop moving.)

      But likewise, sometimes these sensors providing our feedback fails in themselves. So it can be wise to have redundancy here, and if a disagreement is noted between our redundant sensors then we likewise stop. (there is far too many machines that fails spectacularly due to a broken sensor and lack of redundancy… Boeing’s angle of attack sensor is a good case study here.)

      Limiting overall power of a machine to a level that is deemed “inherently safe” for the application is also something to consider. All though not always an option.

      However, safety is often far from trivial in practice. There is often a lot of nuances one don’t notice before hand.
      But likewise, a lot of safety issues can be avoided if development is given some time to focus on safety, instead of rushing towards product-release/project-completion.

      1. It may well have had those, I can’t find a better detailed breakdown of the accident – but a kids finger is likely smaller than the chess piece, and it doesn’t take much force at all to break a finger, so even tuned down to a power level so weedy it can barely hold/move its own weight…

        1. Fingers are rather fragile things indeed.

          However, the machine should have a rather decent idea of where a chess piece is.
          And therefor know when to grasp, and also know what diameter it is looking for.

          And even if a child’s finger is smaller than the chess piece doesn’t make our assessment if we picked it or not all that different.

          We expect grasping something of X diameter, if we see something that is Y = X +/- 1 mm, then yes it is likely the chess piece, if it is wildly different, then it isn’t what we expected, therefor we should release.

          (however, non round pieces will be a thing to consider differently.)

          Another safety feature is to have a load cell for the head of the arm, not directly measuring grip force, but rather the tugging force of whatever it is holding. If the thing even shows a bit of force, then it likely isn’t the light weight chess piece, but rather something heavier, or something connected to something else. And therefor we should release.

          Then there is also the idea of using an optical fence. If hands comes into the courtyard, then we stop. Just IR diodes and receivers is simple enough, and shouldn’t have major issues indoors.

          1. Yes it knows where the chess piece is, doesn’t mean it knows a kid that presumably hasn’t been told better has managed to put their finger in the path (and the operator didn’t react and hit the e-stop early enough either) – even a magnet gripper wouldn’t always help here. Anymore than a infant trying to body block an adult is going to work out well for that infant – the power and mass behind even a really lightweight mechanical arm can be way more than substantial enough to break the as we have mentioned rather delicate fingers…

          2. A visual system that can see the target could limit the possibility of a finger getting clamped. A Pixycam could identify/confirm the piece being moved, but all you’d really need is enough processing to say “chess pieces have round tops–Hey that (finger) isn’t round” and stop the movement until the path is clear.

          3. The only ‘safe’ solution is for the robot to only make its moves while the human is holding two buttons down that are far enough away and apart to be sure the human can’t physically be in the danger radius. And even that isn’t really certain, and I’d argue would actually make the robot on the whole more dangerous to be around in this case – its still potentially lethal but now everyone assumes its safe even when its got power as the permission to move buttons are not depressed.

            But software can glitch and buttons can stick or outright fail short/open without it being apparent to the user. So if everyone is treating it like it can’t hurt them no matter what…

          4. A large guillotine I saw once used not just two push buttons, but they had metal buttons and ran a small continuity test through the person touching them to ensure that they had two hands of the same person on it, not something accidentally leaning on a button or something.

          5. ” the power and mass behind even a really lightweight mechanical arm can be way more than substantial enough to break the as we have mentioned rather delicate fingers…”

            If the arm moves sufficiently slow (0.1 m/s or less), it wouldn’t be much different than placing a hand onto an almost stationary object. Even if it has practically infinite power behind its movement, it won’t have sufficient speed to rapidly impart any energy into whatever it is hitting. (and it isn’t like children grasp a lot of other moving objects on a daily basis)

            One can also cushion the blow by padding the arm, but then one is likely moving too fast.

            However, it wasn’t speed that broke the child’s finger.
            The action that broke the 7 year old’s finger were when the arm placed the chess piece back down on top of it.

            Here a simple solution is to have a spring loaded gripper able to retract 1-2 cm (with feedback, could just be the E-stop), this would give the machine sufficient time to notice that things aren’t as they should. Since the spring loaded part started retracting ahead of expected and therefor the program knows that it has hit something that shouldn’t be there. Likewise does the spring loaded mechanism give the person more time to pull their finger away (since it wouldn’t apply much clamping force to speak off), something the child tried. But since the machine were far too rigid, they simply couldn’t.

          6. >If the arm moves sufficiently slow (0.1 m/s or less)

            If it moves sufficiently slowly you die of old age waiting for it…

            Not that you are wrong, but it pretty much entirely negates the point if it can’t function in a sane timescale. And even at 0.1m/s if you go and put your hand between it and the destination it will still crush it with ease (unless as well as being very slow it has no mass and/or stiffness).

          7. “And even at 0.1m/s if you go and put your hand between it and the destination it will still crush it with ease”

            I see someone completely forgot the main point I have been talking about this whole time.

            So I will reiterate again…

            One shall have feedback for how much power is currently used for a given point in time during a move, and that one shall have an anticipation of when an increase in force is expected and not.

            If one moves from X to Y and knows one expects to hit nothing along the route, then one don’t expect much force at any point along the route. If force is encountered, then something is wrong and one shall stop. (some inertial loading one will have to account for if one desires higher acceleration.)

            If one moves from X to Y and knows that Y will be at a position one expects force, then it is a question of tolerances and latency for how much before Y we consider an increased force as expected. But still, if the force increases too early, then something is yet again wrong and we shall stop.

            Likewise can we make the most safety critical bits less rigid. Often through linear movement held against an end stop by a suitable spring. Often eliminating most crushing hazards.

            Safety is largely about estimating what will happen and when, and then stopping in a safe manner if we fall outside of our estimate.

            And with feedback of this kind, one can often operate at noticeably higher speeds before crushing becomes an issue. (though dependent on reaction time and how long it takes the machine to stop moving.)

            The 0.1 m/s is mostly an example of a safe operating speed for almost any equipment. It isn’t fast enough to crush bones or even leave a bruise. (unless concentrated down to a sufficiently small point.) Realistically, even 0.5 m/s is too slow to cause harm from getting hit. Crushing is however still an issue, but as I have stated earlier this can be solved.

          8. Not missing it at all, but no matter how slow you go the mass/stiffness/power of the robot arm can easily cause damage.

            How fast something is moving is of no relevance to the harm it can cause you – going as near as makes no odds static relative velocity at impact could still kill you with ease with a crush against something else if its got enough inertia or driving force – though being that slow you probably die of hunger/thirst from the pinning action rather than being turned to jam by the rib crushing ‘unstoppable’ force. All going slower gives you the machine operator or the machines internal logic is more time to react, doesn’t take away from the force that can be applied, so the maximum impulse might be quite low, as the time to finish squashing all the softer fleshy stuff and really apply the full power is so long, which is safer, as you have time to react, and are likely just slowly pushed away – just of no use at all if you do get caught between it and something else and its not stopped quick enough.

            Even if its got a superb position accuracy and shuts down as soon as it encounters forces just the tiny bit over the expected peaks of the sensors noise floor for this move in places it doesn’t expect to hit anything harm is possible, and while its actively expecting to pickup/putdown something the positional accuracy is largely out the window as the object usually isn’t 100% repeatably always held exactly in x position, as its a real world object – in this case the wildly differently sized and very non-uniform shaped chess pieces, so some resistance in the window where the part is expected to hit the board/grabber is 100% expected! To the machine that just means the part was rotated differently on the board or held very slightly differently in the actuator, not that something else got in the way…

            (though get slow enough you’d have to insensitive to all stimuli to not be able to move out of the way as it moves to crush you)

          9. “How fast something is moving is of no relevance to the harm it can cause]…” is a largely unnecessary paragraph. Since yes a machine is obviously dangerous if it doesn’t stop…. While my whole argument is, “It shall stop if X condition happens.”

            But going on.

            Yes, inaccuracies in picking something up and placing it back down do exist. But saying, “there is inaccuracies!” makes you sound like a mathematician with no engineering experience. We should look at inaccuracies and consider if they are sufficient to be problematic, tolerance stacking and all.

            For a lifting the typical chess piece, the run to run variance is likely quite small. (in my own experience I see little reason for it to venture beyond even 1 mm.)

            As long as our variance is sufficiently small, then a finger is going to result in a considerably bigger variance.

            In regards to positional accuracy. Being half the diameter of a small finger is sufficient. So 2-3 mm at most (to be safe to practically all ages). And most often we will have better positional accuracy than this.

            Rigidity however needs to be better for better positional accuracy, and that in turn means larger crushing risks since the thing won’t give.

            But yet again, the main crushing risk if when the arm goes down, a situation a spring loaded mount for the gripper would also solve crushing issues. Since even if it starts to clamp down onto the user, there is a couple of cm worth of fairly low force travel that the machine itself never considers using. (not that the machine in the incident had such.)

            And with a spring loaded mount, it can have the end stop provide an electrical connection so that it notices if the mount were to move back against the spring. (ie, informing it that it shall stop.)

            In regards to getting hit by a moving arm, this isn’t all that dangerous either. Low speed movements don’t impart a lot of energy. Even 0.3 meters a second is all things considered fairly slow, it will likely hurt. But damage is very unlikely. And 30 cm a second is quite rapid. (about a foot a second) Nor is the machine operating in an enclosed environment, so crushing up against something is likewise unlikely. (and it should still stop when confronted with unexpected resistance.)

            However, the idea isn’t to make the machine completely incapable of inducing any form of harm. (because that is unrealistic) But rather making the machine incapable of inducing serious or even minor damage. It might in the worst case still inflict discomfort.

            And in the end.

            The whole concept I am talking about isn’t “new”, or unique.
            A fair few industrial robots can do this, and do actually do this. If assembling two pieces and seeing forces outside of the norm, then a lot of industrial robots can alert the operator of the issue. Instead of potentially breaking expensive equipment that likewise can be hard to quickly replace.

          10. And I don’t disagree with you – my point is NOTHING is without the potential for injury with these things, so some minor injuries from time to time are to be expected, no matter how safe its supposed to be and that this was a not a major injury… I’m not against robot arms etc or saying they can’t be perfectly adequate in safety, just that stuff can always go wrong and perhaps that is what happened here, despite sufficient safety precautions.

            You seem to have rather more facts than I can find about the setup of this arm to speak so confidently it did or didn’t have x options…

            But even if they had everything you suggested and nothing at all goes wrong my point is it STILL CAN cause harm. There is no such thing as foolproof safety – such as a kid putting their finger of comparable size to the expected target right into the spot the gripper is about actuate on, and that finger not being solid and slippery plastic but squashy flesh and tiny bone can’t take the clamping forces, or perhaps it can but then not being heavy and/or tough enough to take whatever movement happens before the robot automatically stops when the forces are unexpected.

            Which for a prolonged period may well be the case as the forces are likely not going to be unexpected enough to trigger immediately, as in the real world sensors have noise and there is move to move and run to run variance as the grease in the joints changes temperature/ages and the parts wear in etc. Which gives you an operating window of expected that isn’t all that narrow if you want the machine to actually work rather than need resting every other movement.

            Then remember as humans we are rather flexible and likely going to move with the robot in the hopes of avoiding injury and so exert very little force, till we suddenly do run out of flexibility to match a change of movement or can’t move fast enough around the chessboard in the way…

            And as we all have already agreed fingers are delicate, moved in the wrong direction really really delicate. So even if you set the unexpected threshold pretty damn close to the point the machine never finishes a move without a reset quite likely enough to harm a finger. Even with everything you suggest to make the robot safe and no errors in the machine a finger injury is easily possible, it just takes bad luck, perhaps some ‘lazy’ programming assumptions (like nothing unexpected should ever be between the chess part and the actuator and no differentiating between tall and short pieces – so just telling the machine to go down till it makes contact, at which point a finger above a short game piece, a pawn say is within the expected height being still lower than the tallest part that is usually the Queen or King), then maybe add some stupidity/ignorance to create a human error too.

            And all that is assuming nothing actually goes wrong in the machine…

      2. Limiting speed may actually make it more dangerous.

        No joke, one of my machines had to increase speed in its most dangerous point. It was slow enough that no one could hear or tell it was moving.

    2. A minor injury isn’t in its own right a major problem, or proof the setup wasn’t sufficiently safe – industrial robots could trivially kill an adult if not treated with the right caution, so a tiny injury that almost everyone will do to themselves without any outside help at least once in their lifetime…

      Turning everything into a witch hunt is neither helpful or perhaps even remotely justified. Look at the situation and precautions taken first, maybe add a new safeguard if needed.

      The kid is a chess player, not a moron or toddler that can’t understand the risks if told about them and what to do/not to do. They clearly had observers to deal with trouble as well. Maybe they didn’t do everything right but equally maybe they did – its not like your 3d printed arms or ‘soft’ grippers are 100% safe and reliable either… So this really minor injury is just the kid winning the shit happens lottery…

      1. “ a tiny injury that almost everyone will do to themselves without any outside help at least once in their lifetime”

        Most people don’t break fingers ever. I know some people who have, and you can usually spot it because their fingers are wonky. So this is a potentially life changing accident. This isn’t a graze.

        1. Folks break and fracture their fingers pretty damn often – the wonky fingers that can result of break just means it was a bad break that set badly.
          You have almost certainly at least put a minor fracture on some of your finger and just thought it was bruised as it hurts a bit but works, and even pretty bad breaks can heal flawlessly and be functional(ish) but sore fingers while the bone is broken…

          1. Ok, if you’re counting those kind of breaks, but that’s not what this was, and pretending it is is disingenuous. The kid required a cast.

            So once again, this wasn’t a minor and common injury. Stop pretending it is.

          2. Without actual medical evidence or a better breakdown of the accident and with the kid being able to play chess again the day after – which means no massively strong painkillers as those futz with your mind way to much to play chess, and not going without in a stupidly high amount of pain as you can’t think straight then either, all rather suggestive the injury was pretty minor.

            ‘required a cast’ when dealing with a finger could mean anything – it used to be common to immobilise a finger on any injury here till it was realised its 99% of the time really not worth it the finger can heal just fine and better without.

      2. Nah, complete lack of consideration to safety from the robot operators/designers. See the operator frantically trying to disable the arm with his tablet. I see no E-Stop in an easily accessible position to the operator, the most basic of safety devices. I don’t see how you can pass blame to the victim when such basic safety is not provided.

        1. If there really is no e-stop at all, and really aught to be more than one, you have a point and I’d be rather surprised.

          The one thing you see fairly constantly it seems to me in after accident studies isn’t that the right safety feature wasn’t there, but that the operator didn’t use it, probably because they were panicked and trying to use the ‘normal’ controls, or sometimes because it was so obnoxious they actually disabled it and can’t undo that mistake quickly either.

    3. we have cobots where I work and we always put light barriers around the things… yes they will stop if they bump into something, but during a demo of one a few years ago I watched it flip out, and punch our conference room table with a heavy thunk and stayed there… now if your hand is between this tripped robot and the table you would be having some angry words about it

      1. Honestly concerned how far I had to come too see this. So many comments about how to tell a finger from a chess piece, so few about not moving at all when someone is in the play area. When I heard about this it was said the kid took their turn too soon after the robot, in my mind there should be a light curtain between the kid and the board that when broken stops all movement on basic redundant interlock systems. Then no mater how quick the kid moves if they are in the play space they won’t get hurt. Also depending on setup it could cut movement of the robot incase of code freakout and it tries to reach through the curtain towards the kid.

  3. When I aligned my own laser cutter’s optics. I put a sticky note over the mirror I needed to aim at, closed the lid, pulsed the laser. Noted where on the note it charred, and made an adjustment before closing the lid for another pulse. Eventually the laser hits nice and center on the mirror. Then it is on to the next mirror.

    The important part when working with dangerous equipment is just patience and considering “how can this go wrong?”. A lot of accidents are due to generally rushing things.

    1. Good point. And for pulse laser focusing, you usually use a target like that as well, because you simply can’t see the super-short pulse. So you just try to get the smallest dot on the paper or wood test scrap.

      Now that I think about it, I can’t really imagine a scenario where focusing by goggles is necessary. Although that’s always the “special case” that people tell me they need them for.

      1. As long as the laser is in an enclosure I can’t see much reason to wear glasses, especially around powerful ones that laser “safety” glasses wouldn’t do much against regardless.

        Pulsing the beam for alignment is so much more trivial and safer. One just have to start at the source and go towards the destination. Slow and safe.

        However, if one fiddles with free space optics and puts things in and out or do other crazy stuff, then perhaps one wants to keep the beam on. One thing would be if one has to line up the phase of two beams for something, but at the same time doing that by hand must require a delicate touch unless it is some deep IR lasers…

  4. One of the members of my local hackerspace is so completely glib with safety that we are waiting for the day he comes in partly blinded or we hear word his homemade high power battery packs caught fire.

    He’s been repeatedly warned and had plenty of folks with more engineering and real world lived experience try to give him the benefit of hard won learning, but he makes tons of money in AI dev and thinks he’s capable of surpassing anyone’s skill in days because bigbrain mode.

    Our space has a very practical take on shopns7afety I think, and we’re not nervous Nellies about dangerous tools and processes, but hooboy he’s gonna get hurt some day.

    Thankfully he’s taken to doing his blinding/fire hazard projects away from the space, but only because seems to understand at this point doing it there would get him a ban, not because he understands that blind means blind and lithium battery fires don’t give warning. Sucks that some folks refuse to learn about danger without firsthand experience.

    1. For my money, these are two very different dangers.

      A fire is no big deal. I cook pizza over fire. (Not a lithium-ion battery fire, though. And not indoors.)

      OK, too blase, but a fire extinguisher or even just a lot of water fixes up a fire quickly, if messily. Nothing fixes up a burnt retina ever. I would spend a lot more on precautions to avoid the irreversible.

  5. The real thing with the simple ‘obvious’ safety stuff is being cautious/smart enough to know when you don’t know how to handle everything this situation could throw up and then taking the time to really think about it (or look up the training courses if they exist).

    In short with every new toy/tool no matter how safe it might seem really think through and take it slow as you get to learn it, or go find a greybeard in the field and so get to jump right in with proper guidance!

  6. My advice: unplug before opening. Common sense, yet a momentary lapse on my part resulted in handing over thousands of dollars to the regional burn center.

    As for the chess robot, mechanical limiting. Duct tape (or better) a chunk of metal to one jaw just smaller than the smallest item intended to be gripped. No help for items smaller than fingers, but could certainly prevent damage to products in manufacturing.

  7. Always great to see more focus on safety. As somebody who’s helped run a makerspace, disseminating safety knowledge in a way that sicks with people (even the most basic “put the lid on flammable liquid containers” and “turn off the soldering iron, hot glue gun, hot plate”) is a big challenge.

    “It’s our jobs as the folks who do know the secrets of safety to share them with others.”

    I’ve noticed that sometimes safety related comments get deleted (it’s certainly happened to me, and I’ve seen other sensible safety comments get deleted as well). Care to comment on this?

    (Not trolling here, just calling attention to something HaD could do better)

    1. Regarding the ‘turn off…’ issue. At work, such things are on a timer powerstrip, so they automatically turn off after 15 min. Minor inconvenience if you’re doing something intricate, but should stop us having another lab fire…

      1. Thanks for reply and tip. Great suggestion (and we did something similar for more dangerous tools), but feel it doesn’t help with the “building a culture of safety”, since the time means one less thing to even know about (then somebody plugs into a non-timer socket for reason x, and has never had to remember to turn off before…). Not saying your idea is flawed or not worth it, just that it’s still a challenge to build a culture of safety.

        Signage also helps, to a certain point…

        1. We tend to use soldering equipment and anything else possible with an auto off on activity feature. It’s not obvious that it’ll time out and there’s no notice that it’ll do so but it’s a nice safety fallback.

          Not including simple safety circuits thinking it’ll encourage lax behaviour doesn’t tend to work out well in practice. See safety belts in cars, racing and otherwise, as a case study example.

    2. I’ve never seen a reasonable comment related to safety go missing if its not a later part of the chain with a really toxic roots anyway…

      I like Alphatek’s timed plug idea, simple and easy to execute. Though if you have proper workstations to solder at I think i’d go digital smarts for the shutoff (which also provides authenticated users only options) – if nobody is moving in the narrow field of the PIR to be at the station turn off after 2 mins, as when you are on a longer job, especially if there isn’t any really clear audio/visual warning your timer is up its going to really be annoying, and potentially harder to recover from the mess you make as the tip goes cold when you didn’t expect it to…

      1. My relatively cheap soldering station has auto-cooldown almost immediately once you release your grip on the iron – the station itself has a big bright temperature indicator so you can see that it’s gone to standby; picking it back up wakes it up and (as Inhibit noted) brings it back to temperature pretty quick. I’m pretty conditioned to use the stand from my old “it’s just on” soldering iron days, but it’s been handy for my kids to have that backup safety as they’re learning.

  8. Sometimes the inherently dangerous “hobby thing” was discovered accidentally by someone who has no personal connection with industrial processes or safety measures typically taken to mitigate them.
    That idiotically dangerous “Lichtenberg figures” craze was obviously found by someone goofing around with jumper leads and mains voltage, but they never bothered to look for a sort-of close industrial process like arc welding and check to see what sort of equipment and safety gear is used to make it as safe as possible.
    Using electrode holders like that cover all of the live bits near your hands for both leads and wearing heavy welding gauntlets like should have been the minimum precautions, but then all the people trying to copy the process either can’t be bothered to take all the effort for a one or two off, because “it won’t happen to them” or even understand how inherently dangerous it is and why the minimum safety gear is essential…🤷

    1. I really think it’s a case of not knowing.

      I grew up very close to the real world. Fixed house electrical, repaired lawnmowers, ran with scissors, made small fireworks, etc. But until I met someone who was into high-voltage foolery, I had no idea of the particular risks — and moreover tricks of the trade to mitigate them. No such thing as “common sense” above 1,000 V.

      Same with lasers. I learned the “keep it in a box” mantra from fellow hackers, although I’ve read up on the professional rules/regs too.

  9. This reminds me of three lawyers who came up with the idea to wreck a circular saw every time you saw a piece of wet wood, or accidentally it a nail or other conductive part in the wood. with a USD300 or so repair bill for replacement parts.

    They managed to get it patented and due to heavy lobbying made the thing almost? mandatory in all schools and probably on other area’s too. A bunch of (very likely “sponsored”) youtubers liked the think, but a few years later and after 5 or more wrecked saw blades and replacement cartridges they don’t like it as much anymore.

    There is also another company with a far superior product that could stop the circular saw blade just as safely, but without any damage to either the machine or the saw blade, but that was pushed out of the market due to patent abuse.

    Before finishing this post I watched some more youtube vids’ about what others think of that saw, and it turns out it also falsely triggers on unstable mains voltages or frequencies. And they still use the same sawblade wrecking method to stop saws.

    The result is that you have to wait many years for the patents to run out before you can buy an affordable system that does not wreck your saw blades or use expensive single-use cartridges.

    1. Ah, the good old “misusing tools is the tool’s fault!”. If you’re running wet wood with nails in it though a tablesaw, you’ve already messed up beyond what a sawstop can help you with and are just paying the idiot-tax in replacement blades.

      There is no magic that will decelerate and RETRACT (the important bit) a high speed spinning blade and instead gracefully decelerate it down to zero RPM without gracefully decelerating it through your flesh in the meantime. Arteries are mm from the surface of the hands (and in particular, wrists) you are waving next to the spinning death-wheel, half measures don’t cut it.

  10. I’ve always found the most effective safety guidance is showing people a video of how it can go wrong – one of my previous employers used to be quite good at this, you develop a respect for battery systems when you’ve seen the video of a spanner evaporating or a battery exploding and every time you have your face near one you see that video in your mind and take extra care.

    Showing a video of a runaway robot arm (real or simulated) breaking some stuff would likely have a very similar effect on most folks and takes all of 30 seconds.

    I’m not suggesting German Forklift Safety Video levels of gore, but demonstration beats explanation in a lot of cases.

  11. Remember: “common sense” works in common situations. Uncommon situations (multi-thousand RPM spinning objects, high velocity metal pieces, plasmas, lasers, high voltages and currents, etc) are not well served by common sense and require dedicated and more esoteric precautions.

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