minecraft screenshot of a simple automated smelter. It's just a single furnace, but there's redstone behind the wall and floor that takes any charcoal from the output chest and recycles it into the fuel input, so if i give it enough logs in the input it'll keep itself fueled
https://pool.jortage.com/glaceonsocial/media_attachments/files/111/337/254/957/581/972/original/1ea369d8bfd44bef.png