Nowadays security is the prime concern in our day to day lives. Through this secure access system, only that person can enter into a restricted area who knows the correct code. This simple circuit is built around a transistor with a few more components like relay, diode, capacitor, switches and resistor.
Fig. 1: Prototype Of Secure Room Access System Circuit On Breadboard
This electronic lock is built with the help of simple active component. In this secure room access circuit, we are using total 8 push button switches Out of these 8 switches, 4 are connected in series at the base of the transistor with the help of a resistor (R2), and remaining four are connected in parallel through a resistor (R1). In this circuit we have used S1-S4, which when pressed in a sequential manner, energize the relay for a specific interval of time to unlock the solenoid-operated lock. If you press any of the buttons from S5-S8 in between the correct code then it will put the transistor to ground and relay will not be energized.
For mounting mix all eight switches and fixed it outside the entry door, now only the authorized person knows the correct code and gets to enter into the room. You can also increase or decrease the number of switches as per your convenience or use numeric keypad available in market in place of a push to on buttons.