Thermal Runaway
My Ender 3 went into thermal runaway today (I shut off power just in time) just before I started to print parts for my Rat Rig build. I checked the thermistor was in place post failure. I also had upgraded the mainboard a while back and has octoprint, and I think thermal runaway is enabled on both. I am going to replace the thermistor as well as update all firmware, octoprint, etc. I know my Ender 3 has needed some TLC for some time, but this isn't the first printer I've worked with to go into thermal runaway. But this lead me to a few questions, especially to add more protection to both this and the rat rig:
1. Are there any hardware solutions to stop thermal runaway? Something like a fuse in the heater line that could trip if too high current too long? Or a setup which uses a secondary thermistor and a relay to cut power to the heater over a maximum value?
2. Redundant thermistors and firmware solution - Any way to incorporate multiple thermistors and some kind of filter where if the error between the thermistors exceeds a certain amount to shut off the heater?
2.1 Some way to connect a smoke detector to a Pi which signals a relay to shut off or something?
3. Any other layers of protection hardware or software that are more than single fault tolerant to give better peace of mind?
14 Replies
Klipper with shut down if an adc exceeds max_temp
blank-aquamarine•2y ago
1. Heated bed has thermal fuse, i.e over 127c it cuts power, but also it has the standard monitoring of expected temperature, so if it heats for xx time and it doesn't see a xx C* increase it shuts down, this can be configured and customised in klipper for both bed and hotend
2. i do believe so? there's a few people in #high-temp that are using multiple heaters atleast, would stand to reason that you can use multiple thermistors aswell
3. the RR setup is quite solid, i've gone over the wiring many times with a thermal camera to spot any issues
Depending on the controller board you have, some have the ability to setup a auto off kind of thing, where it shuts of mains power to the printer via Gcode ( i think)
depending on how the thermal shutdowns and such work you might be able to incoperate that into it, though, i think that's unneccesary as on a thermal shutdown it defaults into a good state for it, fans run at 100% and all heating is suspended etc
I have a separate GFCI breaker on my vcore3. Though I never implemented it, I thought about using a breaker that allows you to feed it current to have it shut everything down in the case of emergency. With a normal GFCI I think you could do this just by feeding a little bit of current into the ground wire attached to the GFCI, but they do make variants that allow for this functionality for controllers
blank-aquamarine•2y ago
that's an interesting idea, the GFCI is the breaker in the panel right? or is it on the printeR?=
on my printer
I also use mine as the main power shutoff
blank-aquamarine•2y ago
gotcha, might not using it's ground fault ability to shut it off risk cutting the breaker in the panel aswell?
If it is a GFCI breaker - yes. In my particular panel, they are almost all non-gfci breakers (in that case no, tripping my vcore3 breaker will not trip my main panel)
blank-aquamarine•2y ago
that makes sense yeah
That is not how a GFCI works
A GFCI is not connected to GND. And RCD is a better name because of it
/shrug that's what I get for being lazy and not double checking my setup
It detects a difference between live and neutral
I always forget the general name (RCD) cause they are just called GFCI here.
Yeah they are called earth leak switches here. The risidual current is probably due to a leak to eath, but not necessarily. Can also be to a different circuit's live or neutral
Thread hijack🫣
Anyway you could hack the circuit breaker test button like in this example https://electronics.stackexchange.com/questions/394238/turn-off-circuit-using-microcontroller-signal
Electrical Engineering Stack Exchange
Turn off circuit using microcontroller signal
I want to turn off this circuit using micro controller signal to base of Q4 transistor. Can I use the same transistor model for Q4 as for Q3? I'm attaching the picture of schematic from Proteus