Keyless Lock

  
The circuit uses a four-bit latch (Ul). What makes the circuit sequential is that the set input of the first bit latch is tied
Keyless Lock - schematic

to the reset of the second bit latch, and so forth. That ensures that any bit latched will be reset by the previous bit latch. The ECG8314 also has a master reset (pin 9) that is tied to the first bit-latch reset (pin 3), which provides an added measure of security for the lock. The outputs of Ul are fed to a four-input AND gate (U2), then to Ql (used as switching transistor), which is used to drive relay Kl. The EGC8314 has an enable low (pin) that can be used as a timing circuit, if that is desired.




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