Wiring And Schematic

Its easy to build and straight forward. This electronic door lock has a remarkable conception because it uses only one active component. How does it work?

Electronic Door Lock Circuit Diagram



To put the relay in tension the 4 buttons S1 – S4 must be pressed. If anyone of the 4 butoons S5 – S8 are pushed the relay doesn’t switch. The supply voltage must be equal to the working voltage of the relay. One transistor like BD135 can switch up to 0.5A, at the same time 2N2222 can do only 0.2A.