Here is a timer to protect power components for DIY crude battery spot welder : -It charge a capacitor box at t=0 -Then when we put a tension on C4 (with an external switch) it stop the charging process, -Wait a chosen time, -Before to weld with the energy contained in the capacitor box, -Then when the welding process is done, it wait some milliseconds before charging again the capacitor box. It is based on comparators (LM324N) and a timer (NE555).