Showing posts with label code. Show all posts
Showing posts with label code. Show all posts
Wednesday, November 5, 2014
Simple Electronic Code Lock
The circuit diagram of a simple electronic code lock is shown in figure. A 9-digit code number is used to operate the code lock.When power supply to the circuit is turned on, a positive pulse is applied to the RESET pin (pin 15) through capacitor C1. Thus, the first output terminal Q1 (pin 3) of the decade counter IC (CD 4017) will be high and all other outputs (Q2 to Q10) will be low. To shift the high state from Q1 to Q2, a positive pulse must be applied at the clock input terminal (pin 14) of IC1. This is possible only by pressing the push-to-on switch S1 momentarily.
Simple Electronic Code Lock Circuit diagram:
On pressing switch S1, the high state shifts from Q1 to Q2. Now, to change the high state from Q2 to Q3, apply another positive pulse at pin 14, which is possible only by pressing switch S2. Similarly, the high state can be shifted up to the tenth output (Q10) by pressing the switches S1 through S9 sequentially in that order. When Q10 (pin 11) is high, transistor T1 conducts and energises relay RL1. The relay can be used to switch ‘on’ power to any electrical appliance. Diodes D1 through D9 are provided to prevent damage/malfunctioning of the IC when two switches corresponding to ‘high’ and ‘low’ output terminals are pressed simultaneously.
Capacitor C2 and resistor R3 are provided to prevent noise during switching action. witch S10 is used to reset the circuit manually. Switches S1 to S10 can be mounted on a keyboard panel, and any number or letter can be used to mark them. Switch S10 is also placed together with other switches so that any stranger trying to operate the lock frequently presses the switch S10, thereby resetting the circuit many times. Thus, he is never able to turn the relay ‘on’. If necessary, two or three switches can be connected in parallel with S10 and placed on the key-board panel for more safety. A 12V power supply is used for the circuit. The circuit is very simple and can be easily assembled on a general-purpose PCB. The code number can be easily changed by changing the connections to switches (S1 to S9).
Thursday, August 14, 2014
8 Digit Code Lock for Appliance Switching Wiring diagram Schematic
This code lock is useful for appliances requiring exclusive or authorised use by those who know the preset code. If desired, the code can be changed.
The schema doesn’t require additional AND or NOT gate operations at the outputs. It uses two pairs of 4-way DIP switches. The code is set using DIP switches DIP3 and DIP4. Then these two switches are hidden inside the assembly. With DIP3 and DIP4, up to 256 code combinations are possible. The unlocking code is set by the user using DIP switches DIP1 and DIP2, which is compared with the preset code entered earlier via DIP3 and DIP4. If the two codes match, transistor T1 conducts.
8-Digit Code Lock for Appliance Switching Circuit Diagram
The codes are compared using two cascaded 4-bit magnitude comparator Ics (IC1 and IC2). If the input nibble present at DIP1 matches with preset DIP3 nibble, output pin 6 of IC1 (connected to input pin 3 of IC2) goes high. Now if nibble present at DIP2 matches with the preset nibble at DIP4, pin 6 of IC2 also goes high. This high output drives transistor T1 and the appliance turns on via relay contacts.
After use, disturb the positions of DIP1 and DIP2 so that the appliance can’t be operated by unauthorised persons. This will also switch the appliance off.
The schema works off a 5V DC power supply. Hidden switch S0 can be used to manually turn on/off the appliance if you have forgotten the preset code.
Caution. You may use this code lock at your own risk. After all, a clever intruder will try all 256 possible combinations one after the other to break the secret code.
Author : Maneesh Chadha Sorced By : EFY
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