Breadboard Security Lock W/ AOI Logic

Have you ever had your parents barge into room unannounced, and you absolutely loathe it. You require your privacy just as much as they do. Well, now you can take charge of your bedroom with this simple circuit.

In this project, you will learn to create a circuit using AOI logic to create a circuit which will activate with a specific code. Now you can take back your room.

For this project, we are going to need:

• A 9V battery
• Resistors x 2
• Breadboards
  • One normal sized one and one mini one.
  • You can also use Tinkercad in case you are unable to get breadboards
• IC´s
  • 74HC04 x 2
  • 74HC08
• DIP SPST Switch x 4
• LED´s x 6
  • Red x 2
  • Green x 2
  • Blue
  • Yellow
• Notebook Paper

The First step we are going to have to do is establish what we want our logic expression to be. The logic expression is a list of conditions in which our circuit will be true (green light turns on) or false (red light turns on). This will impact how your circuit is wired. For this step, take out your notebook paper and draw the picture you see on the top.

You only want to choose ONE combination, so pick any combination of values in the truth table. There are a total of 16 possibilities. For our example, we have decided to go with the expression: ONE, NOT-TWO, THREE, FOUR (12'34). This will be the only expression where the green led will light up.

Now we are going to start breadboarding. Before we do any major wiring, you´ll have to set up your breadboard like you see at the top. Once that is accomplished, we can begin the wiring process of wiring our circuit.

In order to wire our logic expression correctly, we need to figure out where to put our wires. If you look up on the image, you can see two IC diagrams. The one on the left is an INVERT gate IC and the one on the right is an AND gate IC. Inverts makes a value opposite. For example, if our original value was true (1), it would make it false (0). The AND gate´s function allows us to combine two different variables and make them work together. For example, if you put variable A input 1A and variable B in input 1B, it will then become AB in output 1. This will work regardless if a variable is true or false.

Depending on what your logic expression is, you will need to wire the circuit accordingly in order to fit the logic expression. Since our expression states 12´34, we will need to wire the circuit as you see at the top. If you are still having trouble understanding, here is a helpful video to look at: https://www.youtube.com/watch?v=3Cw-6jSRTtQ

Test your circuit and make sure when you have the correct combination, the led turns green, otherwise, it will be red. If this works, congratulations!!!!!! You have successfully wired a combination circuit. Feel free to do whatever you please with this, and have yourselves a wonderful day!