Digital Lock Project


Posted on Feb 4, 2014

EncoderBit1(LOW) is negated with the hex inverter U5A and sent to the 4-input AND gate U3A along with EncoderBit0(HIGH), the above J-K output (HIGH), and a HIGH value from Vcc. -During these 5 seconds, the encoder knob is rotated so both bits are set LOW. Those 2 outputs are inverted with hex inverters U2A and U8A, making the signals HIGH, and one


Digital Lock Project
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is sent to the Down input pin of the 74193 synchronous 4-bit counter IC while the other is ANDed (U10A) with the output of a second one-shot (U4A). -The falling edge of the 5 second one-shot triggers the second one-shot U4A for 2 seconds. While the first one-shot acted as a delay, this acts as a timer. During those 2 seconds while the output 1Q of U4A is high, the AND gate U10A outputs a HIGH, which sets the ~LOAD pin on the 74193 counter HIGH and effectively activates the counter and prepares it for the next inputs. -While the one-shot is still outputting HIGH and the counter is active, Button3 is pressed 3 times, sending 3 singlas to the Up pin and setting outputs QA and QB of the counter HIGH (b`0011` = 3). The two HIGH outputs are ANDed by U17A and that output is further ANDed by U6A with the Enter button. -As seen above, the correct output is actually the one coming from the U17A AND gate. This signal does not change unless the Reset button is pressed and is then ANDed with the changing Enter button signal. This allows the output to be controlled by pressing the Enter button once the lock is `open`, which is necessary for the second part of the lock. -The output and inverted output of the U6A AND gate, along with a ground singal, is sent over an RJ-11 cable to the Temple of Wisdom Box (wooden Winchester ammo box) which controls a DC motor latch to lock and unlock the lid. -The latch is operated using an H-bridge of 4...




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