Is there a better option than the IOT power switch for controlling the power to Air/Evac/Spindle systems? I am thinking smart plugs were not around when it became available but a Raspberry PI should be able to control smart switches and that someone must have hacked at least one of them for a remote emergency stop switch.
Links are kindly requested.
Smart switches were around. They would also work. I prefer the directly wired solution, just because there is no dependence on wifi (and no delay). But I am sure the smart switch works fine, as long as it works for the current requirements of the accessories.
âMe: Alexaâ
Alexa: <pause><tone>
Me: âCNC offâ
Alexa: âAdding seaweed to your shopping listâ
Often when I want to shut things down, I need it to happen immediately. Mostly it is me realizing I messed up at the start of a job or a tool change. By being able to stop things immediately, Iâve often been able to save my stock or a job.
Personally, I have a more convoluted emergency setupâŚmostly because I like to play with things. I have an IOT relay that turns the router on and off based on the g-code. But in the larger context, that means any time I cut 12V power, the IOT relay shuts off power to the router and vacuum as well. In addition to a mechanical switch on the 12V line, I tossed in an Arduino Nano with a relay (powered by the 12V line). This allows me to have multiple other ways of cutting power. I have a secondary switch and a wireless remote. I soldered wires for an IR flame sensor, but Iâve never installed it. Iâm concerned that it will sense âlegitimateâ heat and kill a long job.
Iâm looking to hack the power button on the outlet to wire to the emergency stop, not rely on a software to tell a WIFI device to save a fingerâŚ
Agreed. But now Iâm confused. In your first post you said you were looking for a âremote e-stop switchâ? remote e-stop sounds like a bad idea to me.
Not sure how you want to trigger it, but all the Alexa plugs Iâve purchased have been rated at 15A, which is more than enough for the MPCNCâŚincluding vacuum and router.
Sound better than no emergency button at all?
No, I donât think so. Thereâs nothing wrong with having your devices connected to relays but as far as an actual e-stop goes I would think it best to be a switch that actually physically breaks electrical connection. I wouldnât want to rely on a firmware/software during an emergency.
If the user doesnât have access to a digital e-stop switch than at least theyâre forced to hit the machineâs power switch. (hopefully they keep their power switch accessible)
Yea, nothing like Alexa misunderstanding turning on the porch light and firing up the router.
Iâm agreeing with the others on this. Having to trust the WiFi network not too hiccup when something is about to be destroyed sounds worse than having to rely on yanking the power cord from the wall. Having a sign like this and a readily accessible power cord sounds like it could be safer than trusting Alexa.
That said, having a remote switch in addition to a physical estop sounds pretty reasonable. Being able to yell for your computer to turn off the machine seems fine, as long as youâre not 100% dependent on it.
I use a light switch wired to the control electronics outlet to kill everything. Not as pretty as a red mushroom, but just as effective.
I donât think anyone is seriously considering using AlexaâŚ
There is a lot of room between Alexa and the estop button. The lower you go, the more likely you are to avoid problems:
A relay that is controlled by Marlin (via wires going into the microcontroller in the smart plug, not wifi) is about as safe as the iot relay. That assumes you do just as good at building it as the commercial product, which is debatable. But from a high level, they are the same.
You could also just use one of the Arduino controlled relay boards (like the sainsmart ones) from Amazon.
Those will all work.
As for what you should do for emergencies, everyoneâs risk tolerance is different. Risk mitigation can be in the form of automatic systems, or easy to manually trigger solutions, or just procedures to avoid getting a finger near the machine while the router has power.
I do think there is a problem of âfalse confidenceâ in safety. Having a safety system that you canât trust (but do trust) could be worse than one you know you canât trust. Having a way to yank power in a âstop no matter whatâ situation is going to be less effective if you are first trying something else that doesnât work.
I have worked in safety engineering before and I think if things as safety and "safety" (with quotes).
Making something cause less damage often involves systems that are smarter, and therefore less deterministic (improves safety).
Making something you can prove wonât cause a catastrophic accident is often done by making them simpler, more deterministic, which might make them worse overall, but you can write down in a report that the machine will never kill someone or start a fire. That is "safety" that has more to do with liability than personal pain.
Adding a relay that is not going to work 100% of the time, or a heat detecting sensor increases safety but decreases the provable "safety". The system is more likely to catch some problems earlier, but hasnât improved its ability to avoid every dangerous situation. If you add in false confidence, then the system may be even more likely to cause injury. I could imagine thinking a bit was safe to change if the relay was off, but if a misspoken Alexa command from your SO in the kitchen causes it to turn on, then you will be putting yourself in more danger than if you had just unplugged it in the first place.
That is to say itâs about as âsafeâ?
Itâs hard to argue against at least @orobâs suggestion of a $4 light switch from the big orange store.
(Itâs not lost on me that Iâm assuming someone can safely wire mains voltage. But if someone can build a cnc machine I feel like that should be a fairly safe assumption. Maybe thatâs wrong on my part.)
Iâve seen someone use one of the big paddle style light switches, with a big plywood flappy stop button that pushes the switch to off on top of it. Gives you a nice big target when shit is going south and covers the on side so you have to switch it on purpose.
The on/off switch I use is very similar to that. Green button to turn on. Big Red paddle to turn off.
The on/off switch is on the AC line going to the control box and a plug for the router. If I hit it, all power to the controller and router dies immediately.
Iâve considered adding a relay to let Marlin turn the router on/off. It would be nice to not have to keep doing it myself. It does give me one last chance to make sure Iâm really ready to start the job before I commit.