6V laser security system circuit. Here I have wired in a such a way that the password is UP,DOWN,UP,DOWN. Here there are 16 possibilities. If you use centre positioned then there are 64 such ...

Circuit and Working. Circuit diagram of the laser security system using a basic feature phone is shown in Fig. 1. It is built around two light-dependent resistors (LDR1 and LDR2), five transistors (T1 ...