HiLetgo 12V 1 Channel Relay Module with Optocoupler Isolation Support High or Low Level Trigger

Module description: Module Size: 50mm * 26mm * 18.5mm (L * W * H) With four fixed bolt holes, holes 3.1mm, spacing 44.5mm * 20.5mm Power Indicator (green), Relay Status Indicator (red) Interface: Input: VCC: Relay power supply + GND: Relay power supply - IN: Signal trigger input (High or Low Level Signal, select via jumper) Output: NO: Relay normally open. COM: Relay Common Pin NC: Relay normally closed. Package Included： 1*12V 1 Channel Relay Module With Optocoupler Isolation How to provide an auto shut-down for Prusa i3 Mk2S? 1. Wired it in parallel with the power switch. 2. Use the hotend fan power as the trigger. 3. When you run a long print ,start the printer and when the hotend fan turns on (at about 50C) you can turn off the power switch. 4.The printer continues to run until the print is finished and the hotend cools below 50C. At that point the relay is no longer powered and the printer shuts itself off.