• on Computer/Software/Internet
  • Published in issue 4/2013 on page 10
About the article

Pattern Lock

Shape recognition for access control

Pattern Lock
Since the touch-screen revolution, fragile, noisy mechanical contacts are a thing of the past; their capacitive equivalents are so much more attractive and their advantages so numerous. The touch-screen interface described in this article is a well-designed application, using Atmel’s QTouch detection method.
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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.

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The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
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Main circuit
Resistors (SMD 1206)
R1,R17,R18,R20,R22 = 100kOhm
R2 = 150kOhm
R3 = 1.2MOhm
R4 = 47kOhm
R5,R6,R7,R23 = 4.7kOhm
R8,R9,R10,R14,R15,R16,R19,R21 = 1kOhm
R11,R12,R13 = 470kOhm
C10,C15–C18 = 100nF 50 V
C11-C14 = 4.7µF 16 V
C19,C20,C21 = 4.7nF 50V
L1 = 4.7 µH 0.75 A, e.g. Bourns type SRR3011-4R7YL; Farnell 1828144
U1 = TPS61070DDC (Texas Instruments) Newark / Farnell # 1461062
U2 = MAX6956AAI (Maxim IC) DigiKey # MAX6956AAI+T-ND
U3 = ATtiny88-AU (Atmel), programmed, Newark / Farnell # 1704570
D10,D11 = BAT46W-V
Q1–Q6 = BSN20, Newark / Farnell # 1081309
J6 = battery holder for 2 AAA batteries, e.g. Keystone type 2468, Newark / Farnell # 1650679
J7,J8,J9 = 6-pin pinheader, 0.1’’ pitch
J10 = 6-pin (2x3) pinheader, 0.1’’ pitch
J11,J12,J13 = 3-pin pinheader, 0.1’’ pitch
J14,J15 = PCB screw terminal, 5.0mm pitch, e.g. CamdenBoss type CTB5202/2, Newark / Farnell # 1717001
RL1,RL2 = reed relay, e.g. Celduc type D31A3100, Newark / Farnell # 1214549
PCB # 120579-1
Acrylic sheet, dim. 60x60x3 mm, PLEXIGLAS® led (truLED) White WH72 GT, www.plexiglas-shop.com or www.acrylite-shop.com
Touch circuit
Capacitors (SMD 1206)
C1–C9 = 100nF 50V
D1–D9 = LED, blue, SMD 1206, e.g. Kingbright type KPTD3216QBC-D; Newark / Farnell # 8530050
J1,J4,J5 = 6-pin pinheader, 0.1’’ pitch
J2,J3 = 3-pin pinheader, 0.1’’ pitch

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