Posted on Mar 13, 2013 4043
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
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.