The PotLock




Introduction: The PotLock

About: radom diy projects

this is a 3 digit combination lock with potentiometers, logic gates and differential comparators

Step 1: Connection Diagram and Parts

i use (take a look at the links)

    2x lm339:

    1x 74HC02:

    1x 74HC10:

    6 resistors 10k

    6 potentiometers 100k

    the voltage is 5v DC

    Step 2: How Its Works

    with the Differential Comparators you can compare different voltages

    look the diagram for the connections

    if the lm339 output 0 is on

    so i use NOR gates,i connect the outputs from comparators to the NOR inputs

    and the 3 outputs from the NOR gates to the inputs of a triple NAND gate

    when the left potentiometers are at the same position with the right potentiometers

    the output is 0 (ON)


    Step 3: Leds

    if you want to see how the circuit works use leds at lm3391,74HC021,74HC10 outputs like the picture

    Step 4: The Combination

    print the numeric pads for the potentiometers for easiest setting of the combination

    Step 5: End

    you can use it just for education or you can lock something like box with a magnetic lock, add at the output a

    PNP transistor with a relay or a N-Channel mosfet to control bigger loads than one led...

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      5 years ago

      Interesting project. And you made it without an Arduino. That in itself is refreshing to see.


      Reply 5 years ago

      thanks a lot!

      My first arduino board, the arduino leonardo broken at the first week so i try to learn about PICs. Arduino is very good but we cant use arduino everywhere and we mast not forget the clasic electronics