About: A normal nerd filled with ideas, working on projects which benefit people and environment. Want to educate people about my projects and ideas... Interested in learning from others toooo.......

Considered one of the greatest invention of all times lock has proved to be an essential part of man’s life. Apart from safe guarding one’s valuables, it also provides an assurance to safety too. Keeping the house safe, cash safety, ornaments, etc. have been the useful purpose of locks. Since technology has changed and demand is growing the development in locks also needs to be changed. Proposed here is a digital lock which tends to be a future Next lock based on digital logic gates. This lock also provides an additional security of raising an alarm when a wrong pin is used. Apart from it also features a Piezo-Electric power which tends to be the Green Technology being used.

Step 1: Principle

Here the concept of digital logic gate is used for implementing the Digital Lock. Using additional logic gates the added security for rising an alarm is implemented. The idea here is to have a lock which works on basic logic gates [given the NXP eval board] and not using any other logic gates. Since basic logic gates are missing they have been replaced by equivalent logic gates using AXP LOGIC GATES itself. The lock has three main circuits namely,

  • Primary circuit or lock circuit
  • Secondary circuit or alarm circuit
  • Reset circuit


  • NXP AXP Eval Board
  • Power Supply - 3 volts max
  • Breadboard
  • Piezo-Electric Plates
  • Some switch and connecting wires


Also known as the LOCK CIRCUIT it involves of controlling the locker safe. The circuit gets activated only when the right pin is used for the lock. For no other combination the circuit gets opened. At the end a AND gate is used for combination to activate for the correct sequence. Shown below is the primary circuit of the digital lock.


In order to provide an added security feature the lock is equipped with a secondary circuit which involves the XNOR gates to activate an alarm if a wrong pin is pressed. The secondary circuit can also be rigged up to lockdown the safe if multiple wrong pins are used. This proves to be an advanced security in low cost components. The unused pins are connected to this secondary circuit and even one pin number is pressed which is not a part of the real pin the alarm triggers or warns people around the safe. Given below is the secondary circuit of the lock.


After completing the transaction one needs to reset the circuit in order to reverse the lock back to its original form. In order to do this a XOR gate is required since it is not available in the AXP IC’s we had a setup to substitute the requirement. It has been replaced by few another logic gates. The reset circuit switch also features a piezo-electric touch pad for triggering. Shown below is the reset switch diagram.


A trending method of producing energy is using piezo-electric plates. Devised here is a new innovate way of using piezo-electric numeric touch pad with the lock mechanism. It features are,

  • Provides a green source of energy so that almost no power or very less power is used by the safe.
  • Gives a input signal to the logic gates when pressed by a user Here a piezo-electric plate is arranged individually for each number and assembled to form a numeric touch pad. Shown below is an experimental setup.


One has a unique set of lock pin number and if any other pin has been entered then the siren goes ON.

The circuit has been designed in such a way that if and only if the CORRECT PIN is entered then the lock opens.

If not,then the siren goes ON alerting the security staff.

The diagrams shown describe the LOCK OPEN & SAFETY CONDITIONS.


Because of the restriction of the availability of logic gates in NXP AXP gates, I have used the same gates which are available same as NXP's AXP logic gates.

The main reason for the use of NXP AXP logic gates is its ULTRA LOW POWER usage.

And this power is readily provided by the PIEZO-ELECTRIC POWER which is installed behind the touch switch's.

Usage of such low power combined with GREEN ENERGY proves to be very cost effective.


  • Used in bank lockers
  • Household rooms
  • Stronghold rooms
  • In business briefcases
  • Commercial market places And many more…..

By using such locks the conventional mechanical locks are replaced and even the new digital locks cannot match this concept because of its cost. Thereby these digital logic gate locks tend to be much advanced by the use of piezo-electricity as source which tends to be another green advantage.



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    5 Discussions

    Hi Kiran,

    Extremely interesting and well documented. Yet - and sorry if I sound dumb - I missed something. The piezo "buttons" or pins can provide electricity. Is it solely used to power the electronic? In other words, you still neeed some batteries or A/C to power the actuator lying behing the actual (physical) locking mechanism?


    1 reply

    Hi buddy,
    NO problem in asking your doubts and getting them cleared.
    BTW the idea of Piezo-plates is to power the IC { NXP } because it needs such a low power so it acts a Digital signal [ 1,0 ] sort of.
    And You need a battery power to power your Lock motors.