About the article

Code Lock

Code Lock
This is a device, built around a PIC16F84-04, which activates an output when the correct access code has been entered on a keypad. This code consists of six digits in the range 0 to 9. The code can be changed by the user and is also remembered when the power is off. A buzzer has been added to provide input feedback, the number of beeps indicates whether the input has been entered correctly or not. This circuit is eminently suitable as an electronic door lock, the switching section of a burglar alarm or as an ignition blocking device.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
R1 = 3kOhm 3
R2 = 4kOhm 7
R3 = 470Ohm
R4 = 4-way SIL array 4kOhm 7
C1 = 47µF 16V radial
C2,C4,C5 = 100nF
C3 = 100µF 25V radial
C6 = 27pF
D1 = 1N4148
D2 = LED
T1 = BD139
IC1 = PIC16F84-04/P, programmed, order code 006501-1
IC2 = 78L05
S1-S12 = pushbutton, 1 make contact, e.g. ITT/Schadow type D6
K1,K2,K3 = 2-way PCB terminal block, lead pitch 5mm
JP1,JP2 = jumper
Re1 = 12V relay, e.g., Siemens V23057-B0002-A201
Bz1 = buzzer 5VDC
K4,K5 = 7-way SIL pinheader
Disk, source code files, order code 006001-1
PCB, order code 004003-1
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