Self-Regulating Heater

I recently found out that PTC thermistors in some cases can be used as a self-regulating heater. I am quite happy having a PLA only printer especially if the chance of burning my house down is reduced. More importantly, it would be nice if the students that I loan out printers to and "promise" me that they will not run it unattended would have a low chance of burning down the dorm.

Has anyone played around with this or thought about it already? (Is there anything on the wiki I missed?) I have no idea of the best way to implement this or even what parts to get. Maybe you could just use the PTC thermistor as a thermal switch in series with a power resistor. You would need to modify the firmware to deal with not knowing the hot end temperature. You could just program in a wait.

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ConceptFORGE
Wally, GUS Simpson, LISA Simpson, THOR Simpson, Sextupteron, CoreXZ

Look into a thermal fuse connected to a relay to power everything down.

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Look into a thermal fuse connected to a relay to power everything down.

The advantage with the above approach could be less house-burns-down points of failure. A self-regulating heater by definition would be hard to overheat. A thermal fuse could become detached or the relay could be broken.

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ConceptFORGE
Wally, GUS Simpson, LISA Simpson, THOR Simpson, Sextupteron, CoreXZ

None of these methods are fool proof, but they reduce the risk considerably.

From what I have read, thermal fuses are too imprecise to be practical, but I stand to be corrected on this.

I have designed and built an electrical extension cable with a "built in" a smoke alarm. When it is triggered (by smoke - but it could be changed for ionisation if needed), it cuts the power to the printer (or anything else that is plugged into it). It uses standard off the shelf components. Cheap to put together.

Supply one to each of your students with the proviso that the printer must only be run from the supplied extension cable.

This is a real problem people. Insurance companies will soon be invalidating household insurance when using a 3d printer, unless we all get our act together.

Another thing I like is an ip camera. I need to get one to check on extended prints.

Hi Dave,

how did you done your cable in detail? And/or maybe a foto available? I am not sure how to make one for myself?

WolfgangA: are you are going to build one for your own use or use the idea for a kickstarter project?

For myself only, all these reports about burning printers started to worry me - and I can't stay all the time with my printer . That's why I'm now looking for a solution.

I used an Aico Ei141 ionisation type smoke alarm together with a Aico Ei128R base unit that houses a switching relay. The base unit clips on to the underneath of smoke alarm to make a nice neat unit. It is a little large but there may be other smoke alarm manufacturers that make one with a relay.
The operation of the relay is only momentary, so another relay is required to make a latching circuit, so the power is cut off permanently until it is reset (otherwise the power will come back on if the smoke alarm stops alarming!).
I housed the second relay in a separate small case with wires out to the smoke detector and to a power extension socket.
For my 3d printer in my living room, I place the detector on top of a book case near the printer and the extension socket is on the floor. I have tested it with a piece of lighted paper and it cuts the power nicely.
I am away at the moment so cannot post a picture.