I want to build some project about metal detector using integrated circuit 555 timer. I already made a schematic in proteus 8 application. I made some change with the original schematic i found on internet. I added some LED on output and resistor 220k. I think my schematic wrong because when i made it in breadboard the project doesn't work. Also, when i run simulation on proteus, led not on.I need help, thank you for your attention.