Ender 3 Emergency Stop Unit
Description
This is an emergency stop unit which disconnects the 3D printer mains power supply by a trigger which comes from the smoke detector, switch or other source that can be added. This is a further line of defence against the possibility of fire. Once smoke is detected the source of heat on the 3D printer is removed. Thus limiting any fire, I HOPE. I have implemented this on the Ender 3 as in the photos. THE WARNING Always have thermal runaway detection active in your firmware. I had to install Marlin 1.1.9 for this to work on my machine. Also, we are not supposed to leave 3D printers unattended. However, we have lives to live and this is not always possible, so another line of defence against fire is this emergency stop unit. The mains power supply is 240 volts. Take care when building this unit as 240 volts is dangerous. If you are not happy in building a unit which involves mains supply, seek support. THE CIRCUIT I have adapted the circuit design from "digimatic" and thus quote this as a source. I use the 555 timer and have added some extras. Have a look at my rough circuit diagram. I use a fan to cool the solid state relay. The white switch/LED is the output "on" switch and indicator. The red switch/LED is a trigger for testing that it turns "off" and the red trigger indicator. From the photos you can see three cable to/from the unit: 1) mains power in; 2) mains power out; and 3) the smoke detector cable. The main components are:- 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 THE BOX I have made 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 "EnergenceyStopTop" part of the box is designed such that the electrical components slide into position. I have isolated the high voltage mains side from the low voltage 12V. THE TEST I set a little smokey 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 virtually immediately and indicated this with a continuous flashing red light. It took another 90 seconds before the EI105R's alarm went off. It took a further 2 seconds or so, before it sent a signal to disconnect the power supply.
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