![]() Lets review a little, The Decimal to Binary circuit outputs a bus of 5 lines, ABCD which represent the binary number and a clock (sincronous output to tell the circuits ahead to act upon the event of pressing a button). Well, you see, upper and lower case A's are indeed different nodes. And finally a circuit to keep the OPEN or CLOSE signal for an undetermined time, and of course an output (thats whatever you want to control with your lock).And, the hearth of our lock, the comparator (its 8 bits ´cause there are 4 bits per digit in the display, meaning that if you want to do a 4 digit lock you will need two of this connected together.) This will tell us if the numbers in the displays are the same as the password saved in the internal memories.As well as an internal memory for our password.Then a circuit to save each pressed number and toggle between displays.Then we need to build the circuit for our two 7-segments displays to work properly, with 4 inputs for a BCD number and of course 7 outs for our displays, ( I used the IC 74LS47).First we need a circuit to decode the 10 possible inputs (0-9) to its 4 output BCD (Binary Coded Decimal), and another output that tells us when any button is pressed.So i drew this diagram as a map to guide me as i build each part of the proyect. First I thought in what was needed to be processed and how. ![]()
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