09-04-2012, 03:09 PM
DIGITAL LOGIC DESIGN ECE 103
WORKING PRINCIPLE:
After construction, enclose the whole circuit, including the power supply (preferably with a backup facility) in a tamper proof metallic box and keep it in a secure location. For optimum safety, use key lock type switches for power (S3) and reset (S2) control. Now open your locker and fix a strong permanent magnet in its door and the reed switch (S1) in the door frame so that when door is closed, the magnet is very near to S1. Now connect the terminals of reed switch to the input of the main circuit using a strong two-core cable.
CIRCUIT ANALYSIS:
Operation of the locker alarm circuit, built around CD4001 (IC1) is straight forward. When switch S3 is turned to ON state, the 12V supply is extended to the whole circuit.
Normally, when locker is closed, the reed switch is also closed due to the presence of bar magnet and hence the output (at pin 10) of IC1 (Quad 2-input NOR gate pack) is in logic low state.
APPLICATIONS:
≈ The locker alarm circuit can be used to protect a locker from unauthorized access.
≈ Can also be used as cashbox watcher!!
CONCLUSION:
Soldering the components in a PCB has become a little easier and knowledge about few other components has been gained. This experience with mini projects will be helpful for future projects in the upcoming semesters.