Friday, August 3, 2018

Circuit Schematic Diagram Electronic Combination Lock using IC LS7220

ElcoHow. - This is one circuit schematic diagram of electronic combination lock using IC LS7220 that very useful for you who want to build activate relay for controlling device on/off.

In this time, we will give you global description about this electronic combination lock using IC LS7220 like in Figure 1 below, beside we give you circuit schematic diagram and component parts used in this circuit.

Circuit Schematic Diagram

Component Parts
  1. C1              1   1uF 25V Electrolytic Capacitor
  2. C2              1    220uF 25V Electrolytic Capacitor
  3. R1              1    2.2K 1/4W Resistor
  4. Q1              1    2N3904 NPN Transistor    2N2222
  5. D1              1    1N4148 Rectifier Diode    1N4001-1N4007
  6. K1              1    12V SPDT Relay    Any appropriate relay with 12V coil
  7. U1             1     LS7220 Digital Lock IC
  8. S1-S12    12    SPST Momentary Pushbutton    Keypad (see notes)
  9. HD1          1    12 Position Header


This is circuit schematic diagram of electronic combination lock using IC LS7220 that can help you to build activate relay for controlling device on/off. The main component in this circuit is LS7220 IC. 

According Circuitstoday site that also published this circuit describe that to set the combination connect the appropriate switches to pin 3,4,5 and 6 of the IC through the header.As an example if S1 is connected to pin 3, S2 to pin 4 , S3 to pin 5, S4 to pin 6 of the IC ,the combination will be 1234.This way we can create any 4 digit combinations.Then connect the rest of the switches to pin 2 of IC.This will cause the IC to reset if any invalid key is pressed , and entire key code has to be re entered.

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

For the key pad, arrange 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 bad guys will be more confused by this.

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