Electronic Combination Lock using LS7220

This circuit diagram could be a simple electronic combination lock using LS 7220. Rangkaian Kunci Digital Ber-password Password Digital is used to activate a relay for controlling (on & off) any device when a preset combination of four digits are pressed.The circuit is operated from 5V to 12V.

To set the mix connect the acceptable switches to pin 3,4,5 and vi of the IC through the header.As an example if S1 is connected to pin 3, S2 to pin four , S3 to pin 5, S4 to pin vi of the IC ,the combination are 1234.This way we can produce any four digit combos.Then connect the remainder of the switches to pin two of IC.This will cause the IC to reset if any invalid secret's pressed , and entire key code must be re entered.

When the correct key combination is pressed the out put ( relay) are activated for a preset time determined by the capacitor C1.Here it's set to be 6S.Increase C1 to increase on time.

For the key pad, prepare switches in a 3X4 matrix on a PCB.Write the digits on the keys using a marker.Instead of using numbers I wrote some symbols!.The unhealthy guys are a lot of confused by this.

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