Ender 3 Emergency Stop Unit

thingiverse

This is an emergency stop unit which swiftly disconnects the 3D printer mains power supply by a trigger coming from the smoke detector, switch or other source that can be added. This adds an extra layer of protection against the possibility of fire. Once smoke is detected, the source of heat on the 3D printer is immediately removed, thus limiting any potential fire. I have implemented this on my Ender 3 as shown in the photos. Always keep thermal runaway detection active in your firmware. I had to install Marlin 1.1.9 for this feature to work on my machine. It's also crucial not to leave 3D printers unattended, however we all have lives to live and this is not always possible, so another line of defense against fire is this emergency stop unit. The mains power supply is 240 volts, take care when building this unit as 240 volts is extremely hazardous. If you're not confident in building a unit that involves mains supply, seek assistance. I have adapted the circuit design from "digimatic" and thus credit them for their contribution. I use the 555 timer and have added some extra components to enhance its functionality. Take a look at my rough circuit diagram. A fan is used to cool the solid state relay. The white switch/LED serves as the output "on" switch and indicator, while the red switch/LED functions as a trigger for testing that it turns "off" and the red trigger indicator. From the photos you can see three cables connecting to/from the unit: 1) mains power in; 2) mains power out; and 3) the smoke detector cable. The main components include: 1. LM555N (https://www.amazon.co.uk/gp/product/B00B2IIA3S) 2. ASH-10DA Single Phase Solid State Relay (https://www.amazon.co.uk/gp/product/B01M074Z1P) 3. YAYZA! 12V 1A 12W AC DC Switching Power Supply (https://www.amazon.co.uk/gp/product/B01N1UPFWY) 4. Smoke Detector Ei105R (https://www.aico.co.uk/product/ei105r-optical-smoke-alarm/) 5. 12V Fan (ebay search "12V fan 40mm") 6. Momentary Push Button Switch Rectangular DC 12V LED 5Pin (ebay) I have created an elegant box for the electronics which sits on top of the PSU on the Ender 3. The two STL files for this are attached. The "EmergencyStopTop" part of the box is designed such that the electrical components slide into position, and I have isolated the high voltage mains side from the low voltage 12V. To test the unit's effectiveness, I set a small smoky fire in a ceramic pot on the printer bed to see how long it takes to disconnect the mains power supply. The Ei105R detected the smoke almost instantly and indicated this with a continuous flashing red light. It took another 90 seconds for the EI105R's alarm to go off, and then an additional 2 seconds or so before it sent a signal to disconnect the power supply.