Article

Intelligent Door Lock

an advanced access control system

The Intelligent Door Lock employs an entrance code to control access to certain rooms or buildings. The heart of the system is a microcontroller manufactured by Atmel. The system employs an electric door latch and has visual and acoustic indicators for ease of use and your personal safety. Access codes are stored in a non-volatile memory device.The flexibility of the system is due to a microcontroller running a program written specifically for the purpose of controlling access to rooms, apartments, hallways and complete buildings.. An all-hardware version of such a system would be much complex and costly. The use of an EEPROM allows access codes to be stored without having to worry about loss of data due to power supply failures.The access codes can easily be reprogrammed by switching the system into ‘supervisor mode’, as will be discussed further on.

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Materials

000051-PCB.pdf

000051-11.zip

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.

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PCB

Download Gerber file: 000051-1.zip

Component list

Resistors:
R1,R2,R3 = 1k?2
R4 = 2k?2
R5 = 1k?
R7,R8 = 8k?2
Capacitors:
C1,C2 = 33pF
C3,C4,C7 = 10µF 63V radial
C5 = 100nF
C6 = 100µF 25V radial
Semiconductors:
D1 = LED yellow, high efficiency
D2 = LED, green, high efficiency
D3 = LED, red, high efficiency
D4 = 1N4148
T1,T2 = BC516
IC1 = AT89C52-12PC, programmed, order code 000051-41
IC2 = 24C04
IC3 = 7805
Miscellaneous:
K1 = 10-way SIL header
S1 = Reed switch and permanent magnet for door mounting
S2 = pushbutton, 1 make contact
S3-S14 = pushbutton, 1 make contact, Marquardt type 6425
Basic switch: Conrad Electronics order #70 68 92
Keycaps: Conrad Electronics
#70 69 06 #70 69 14
#70 69 22 #70 69 30
#70 69 49 #70 69 57
#70 69 65 #70 69 73
#70 69 81 #70 69 90
#70 70 07 #70 70 15
X1 = quartz crystal 12MHz
Bz1 = buzzer, passive type, 6V operating voltage
RE1 = relay, horizontal mounting, 1 changeover contact, coil voltage 6V or 5V, e.g., Siemens V23057-A0001-A101
PCB, order code 000051-1
Disk (AT89C52 source code), order code 000051-11.