I would like to reopen this topic.
I added a thermal fuse as suggested. The thermal fuse will trip at 150 degrees Celsius. I couldn't use the lower (120 degrees Celsius) because I was able to trigger the fuse in really hot applications. I never tried to trip the 150 degrees fuse. That is really high for a bed heater. The heater itself will probably be close to 180 or 200 degrees running at full power before setting of the fuse! Although I mounted the fuse as close as I could to the heater, there will still be a substantial leg between the temperature of the fuse and the heater. Especially because a 500W heater heats up so fast.
I sort of happy with this solution. I every thing fails the fuse will stop the heater. However, I would still like to ad an normal relay so that the firmware can stop the heater before the thermal fuse kicks in. The thermal fuse should be the last line of defence before melting down.
I need to modify Marlin to operate the relay. The relay should be activated at start up and should be turned of if kill is activated. I was looking for the start up and kill procedure but couldn't find it. My admittedly limited programming experience isn't helping with this. Any suggestion on how to do this would be greatly appreciated. :)
I added a thermal fuse as suggested. The thermal fuse will trip at 150 degrees Celsius. I couldn't use the lower (120 degrees Celsius) because I was able to trigger the fuse in really hot applications. I never tried to trip the 150 degrees fuse. That is really high for a bed heater. The heater itself will probably be close to 180 or 200 degrees running at full power before setting of the fuse! Although I mounted the fuse as close as I could to the heater, there will still be a substantial leg between the temperature of the fuse and the heater. Especially because a 500W heater heats up so fast.
I sort of happy with this solution. I every thing fails the fuse will stop the heater. However, I would still like to ad an normal relay so that the firmware can stop the heater before the thermal fuse kicks in. The thermal fuse should be the last line of defence before melting down.
I need to modify Marlin to operate the relay. The relay should be activated at start up and should be turned of if kill is activated. I was looking for the start up and kill procedure but couldn't find it. My admittedly limited programming experience isn't helping with this. Any suggestion on how to do this would be greatly appreciated. :)