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Smoke Detector cuts power

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My Ender 3 enclosure has had a smoke detector installed pretty much since I built it. I recently got around to upgrading it a bit so that printer power would automatically be killed if the detector went off. This was done by using a detector that is built to be linked to other detectors plus a relay designed for use with that style of detector.

The smoke detector was $12.25 at Amazon (prime) First Alert Smoke Detector Alarm | Hardwired with Backup Battery, BRK9120b6CP
The relay was $16.89 at Amazon (prime) BRK RM4 Smart Relay for First Alert

The specs on the relay looked to be plenty adequate for the Ender 3 power draw (15 amp resistive or 1/3 HP motor). I wired the relay into a short (2') extension cord so the printer power gets interrupted if the smoke alarm goes off.

I used some round 3 conductor antenna rotor cable for the connection from cord to smoke detector pigtail. All connections were soldered & covered with multiple layers heat shrink. I didn't bother with an enclosure for the relay assembly, it was already heat shrink sealed as a bundle, so I just taped the connections together to make a neat packet.

Wiring was pretty straight forward. The pigtail for the smoke detector wanted hot & neutral wires (from the plug) plus a third for the signal. The input for the relay needed signal (from the detector) + hot & neutral (from the plug). On the output side, the relay common got a connection to hot from the plug. The socket end of the cord got ground & neutral from the plug end + the relay's NC wire for the hot side.

Tested it out before plugging the printer in (had already checked wiring cold for continuity & shorts). It dropped power on the detector test button being pressed & restored power about 5 seconds after the beeping stopped. This assembly got plugged into the power strip from the UPS I use for the printer.

It doesn't address everything that could go wrong, but if I need to leave the area for a bit it makes for a bit of insurance while I'm out of earshot.

This look really good, well done, unfortunately both items do not appear to be available on the UK Amazon site. I will check with my Electrician if he has something similar. I am amazed that someone has not created an integral power extension unit with a built in smoke alarm for such a purpose. I am aware that you can buy commercial RCCD type units for distribution boards\ consumer units but it would much simpler to have a stand alone plug in unit bought off the shelf. Must be a future crowd funding project there for someone? Thanks again for a great post. Boothy

I have been personally trying to think of a way. If I need to print while away to have some sort of safety. This overall seems like a pretty good idea. Let me know if you find if the smoke detector give any false positives and how far you have it away from the printers.

It is inside the enclosure with the printer, like the original detector. Less than a foot distance. Zero false alarms on either the old detector or this one.

Nice idea.

I think the likelihood of a 3D printer catching fire is WAY overblown, and having done a little research, it seems that there have been, at most, two reported cases. However, these two stories keep getting posted over and over, making it seem like this is a huge problem. Therefore, like so many other things on the Internet, the meme takes off and acquires a life of its own.

I very much like this approach because it doesn't require making modifications to firmware, something that seems to screw up a lot of people's printers. I'm basing that last statement on the huge number of posts, just in this forum, which start "I upgraded my firmware so I could enable thermal runaway protection, and now my printer isn't working right ...".

And, BTW, if you read the most commonly cited story about a 3D printer catching fire, the person who reported the fire says it was most likely caused by the heating element in the hot end falling out. Thermal runaway protection would not have detected any overheating in that case.

My heating element on my A8 did fall out of the hotend and thermal runaway protection did stop it from printing. It does stop it in this scenario at least how I have the way the firmware is set that I uploaded to it. Theirs some lines of code in their for sudden drop of temperature. Which is what happens if the hotend falls out.

I'll pitch in.

Both of my first two Ender 3's (my first entry into 3d printing) both caught fire via the xt600 connectors. I was extremely lucky to be home both times. This was last August and September. My printers sit right on my workstation. I was gaming when I smelled the first signs of trouble, looked over just in time to see a small flame erupt from behind the printer. I was quick enough to shut power off, fast enough that I didn't need to use a fire extinguisher (only the plug itself ignited, but didn't have the strength to spread).

My second Ender 3 came 3 weeks after that one, and within a week I experienced the exact same issue, but caught it before it actually produced a visible flame.

Both printers were replaced, and when I received them, both xt60 connectors were removed and new ones soldered on. I then set up a slightly different system as OP. I have my fire alarms connected to an emergency kill switch. If one, or both, go off all power is cut to the area the printers are in. My computer and octopi's are connected to a UPS. If power loss is detected, my computer will send an email and then goes through an automated shut down.

There was a great deal of concern right around this time about these connectors on the Ender 3's, enough that MULTIPLE prominent youtubers made safety videos, and warnings galore went out on the Ender 3 facebook groups. Though I seem to have been the only one to report actually seeing flames.

Those two stories get told a lot because those are the extreme cases of what could happen. The more you can get printers to take head of those possible failures, the more they can be avoided. I've come to learn there, through the VAST community of 3d printers, that there are many small incidents that could have lead to much worse end results. But because of incidents like those big two, most people have precautions in place.

Those few famous incidents should always be kept in circulation. hehe a good reminder that our printers can be dangerous, even if the risk is small.

I've seen one of those videos:


and it points the finger either at sub-standard xt60 connectors, or improper installation of the connectors, without using solder.

The only point I made above was simply that a lot of people worry about Ender fires, but then focus on thermal runaway as the cause. They then update the firmware in order to add thermal runaway protection. However, the new firmware often causes the printer to malfunction (there seem to be a lot of "I updated my firmware and now it won't print" posts).

However, if the real hazard is power supply connectors, the thermal runaway upgrade will do absolutely nothing to protect from that problem, and therefore you will have spent considerable time, money, and effort to fix the wrong problem.

I am certainly going to check my xt60 connectors tomorrow to see if there is any sign of damage, and I'll also touch them after a few hours of printing to see if I can detect any abnormal warmth.

i ordred a infra red temperature reading device from amazon so i can check the xt60 connector temps with an accurate reading as opposed to using a human touch as your body will not give you numbers to compare.

Phooey. I edited my post and it got "flagged for moderation," which means it's never coming back. This forum software is awful.

The short version of my post is that I don't think an IR thermometer will tell you much because its aperture is too wide to give you just the temperature of the connector. It's the same reason you can't use it to measure the temperature of your hot end.

The point of this thread is the potential fire hazard in your printer, and for something to catch fire, you need to get to the ignition point, which for filament or wire insulation, is way above the 200° C use to melt your filament. Since 200° would burn you instantly, if you can grip the power connectors that we're talking about and barely feel any warmth (which is what I found after I made my post above), you don't have a problem and don't need a thermometer to confirm that.

However, DO get the IR thermometer. I use mine every single day, mostly in the kitchen for measuring pan temperature, over temperature, refrigerator temps, and more.

thanks johnmeyer, i wasnt are of the aperature being such a "wide beam" i get what your putting down. shame about the post as it was a fantastic one. when i first heard about the fire issues with enders i immediately checked my heat bed connections, as i have gone thru losing everything once before waking up in the middle of the am to my house fully ablaze from faulty electronics. the smoke detector auto shut down idea is fantastic.

I have an IR "point and shoot" thermometer and use it almost every day. It is an amazing device, but I think its aperture is too wide to give you a correct reading for something as small as a connector. This is the same reason you can't use it to check the temperature of your hot end, because the heat source is only a few millimeters in cross section, and the IR thermometer is integrating the temp from an area that is 20-40 mm across, even when held near to the heat source.

I still recommend feeling the connector. I did this shortly after posting above and found the connectors mildly warm to the touch, probably about 10-15° F (5-10° C) above ambient, which is normal.

Remember, the point of this thread and others like it is the worry that your printer is going to catch fire. To have that happen you have to reach the ignition point of some material in the printer. The most likely ignition point would be either the filament or the wire insulation. Both have auto ignition temps at levels that (obviously) exceed the temperature at which you are extruding the filament. Those 200° C (and higher) temps would not let you touch the object without extreme pain. Thus, if you can hold a connector in your hand after current has been flowing through it for a few hours, and that connector only feels slightly warm, I don't think you have a problem.

Yeah wont help at all in that case. I do feel people need to check their connections after a few prints and make sure. No odd resistance from bad connections and that is a good idea. Also to routinely check the wires (depending how many prints and that you do.)