About the article

iAccess

an intelligent access control system

iAccess
Surveys show that people are feeling increasingly less safe. Consequently, protecting property and buildings receives more and more attention these days. One of the aspects of such protection is access control. The system described here goes further than most such systems. Besides granting persons selective access to specific areas, iAccess allows you to check who was granted access to which area and when.Nowadays, access control systems are available from quite a few manufacturers. These are usually either quite elaborate systems designed for thousands of users and offering a large number of features, or very limited models that are more suitable for private use. Most commercially available systems use electronic keys, such as magnetic cards, badges, iButtons, or transponders. There are also models that use PIN codes and/or biometric features.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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.

Resistors:
R1,R17-R20 = 1kOhm
R2 = 47kOhm
R3,R4,R25,R26,R31 = 10kOhm
R5,R6 = 1kOhm 5
R7,R8 = 100Ohm
R9-R12 = 27kOhm
R13 = 1kOhm 5
R14 = 1Ohm 5 5W
R15 = 3kOhm 9
R16 = 4kOhm 7
R21, R22 = not used
R23 = 10Ohm
R24 = 2Ohm 2 5W
R27 = 1MOhm
R28 = 330kOhm
R29 = 220Ohm
R30 = 100kOhm
P1 = 10kOhm preset
P2 = 5 kOhm multiturn (vertical mounting)
Capacitors:
C1 = 2µF2/10V radial
C2,C9,C12-C17,C20,C21,C23,C26,C27,C32,C33,C35,C36 = 100nF
C3,C4 = 22pF
C5-C8,C10 = 10µF 16V radial
C11 = 220µF 25V radial
C18 = 2200 µF 35V radial
C19,C31 = 220nF
C22 = 5-40pF
C24,C30,C34 = 22nF
C25 = 100µF 16V radial
C28,C29 = 15nF
Semiconductors:
D1,D2 = 5V1 500mW
D3,D4 = 4V7 500mW
D5-D9 = 1N4007
D10,D18,D20,D21 = LED, red, low current
D11-D15,D24 = 1N4148
D16 = 1N5401
D17,D19 = LED, green, low current
D22,D23 = BYW98
IC1 = AT89S8252-12PC, programmed, order code 020163-41
IC2 = MAX232
IC3 = PCF8573 P
IC4 = 2803 or TD62083AP
IC5 = L6202
IC6,IC7 = NE555
IC8 = LM7805 TO220
IC9 = L200
IC10 = 74HCT126
IC11 = 74HCT04
IC12 = 74HCT08
IC13 = 1x 74HC00
T1 = BC547B
Miscellaneous:
BZ1 = DC (active) buzzer, 5 or 6V
F1 = fuse, 50mAT (slow) with PCB mount holder
F2 = fuse, 630mAT (slow) with PCB mount holder
F3 = fuse, 2A5T (slow) with PCB mount holder
F4 = fuse, 1AT (slow) with PCB mount holder
K1 = 16-way boxheader
K2,K9,K10 =3-way SIL-header
K3,K4 = 9-way sub-D socket (female), PCB mount, angled pins
K5 = 2-way PCB terminal block, lead pitch 7.5mm
K6,K8 = 2-way PCB terminal block, lead pitch 5mm
K7 = 14-way SIL pinheader
K11 = 3-way PCB terminal block, lead pitch 5mm
RE1 = V23057-B0002-A201 (12-V relay, 1 changeover contact)
S1-S4 = pushbutton, 1 make contact
TR1 = mains transformer, 2 x 9V/12VA (e.g., Monacor/Monarch type VTR12209)
X1 = 12MHz quartz crystal
X2 = 32.768kHz quartz crystal
Hea
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