Electronic Keypad Combination Lock

Posted on Feb 5, 2014

When wired to a ten-digit keypad, the circuit will recognize one 4 digit combination out of a possible 5040 codes. When the programmed four-digit combination is entered from the keypad, in proper sequence, LOCK turns on and Lock Status turns off. The lock combination is set by pins 3, 4, 5 and 6 on the LS7220. These correspond to the digits on the k

Electronic Keypad Combination Lock
Click here to download the full size of the above Circuit.

eypad. So if for example you wanted to set a combination of 8462, wire key 8 to pin3, key 4 to input 4, key 6 to input 5 and key 2 of the keypad to input 6. Any unused keys are wired to pin 2. An input on pin 2 resets the lock combination. The keypad must have individual connections for each key and a common return key. The return key is wired to pin 12 of the LS7220. The alternative is to wire a group of switches in parallel.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    1 Watt Linear RF Amplifier
    frequency counter
    Car Wireless Alarm
    cmos 4047 power inverter 12vdc
    LED Flasher Circuit Using Transistors
    60 Watt MosFet Audio Amplifier
    Led Running Lights
    HOLTEK 9200B & 9170B DTMF Generator & Receiver