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Kiddies Toothbrush Timer

Kiddies Toothbrush Timer
The timer presented here is designed to look like and mimic a classic sandglass and should need zero explaining to your kids, the operation being intuitive. If they can switch on the TV and the WiFi router, surely they can operate this timer too. Press the button to start the timer. LEDs light in sequence to imitate sand grains trickling down, and (yes) a modest beep sounds every 30 seconds, as well as when “time’s up”. One LED equals 10 seconds.
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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.

COMPONENT LIST
Resistors
(SMD 0805)
R1 = 1kOhm 1%
R2 = 10kOhm 1%
R3,R4 = 75Ohm 1%
R5–
R16 = 120Ohm 1%
Capacitors
C1,C2,C3 = 100nF 25V, SMD 0805
Semiconductors
D1–D24 = LED, red, SMD 0805, e.g. Kingbright KPHCM-2012SURCK; Farnell # 1686067
D25 = LED, green, SMD 0805, e.g. Kingbright KPHCM-2012CGCK; Farnell # 1686075
IC1 = ATtiny13A-SSH, SO-8 case, programmed, Elektor # 120368-41
IC2,IC3 = 74HC164D, SOIC-14 case
T1 = BC850C, SOT-23 case
Miscellaneous
BT1 = button cell holder and CR2032 battery; Farnell # 2064725
BZ1 = piezo buzzer, Farnell # 1192551
K1 = 6-pin (2x3) pinheader, 0.1’’ lead pitch
S1 = pushbutton, side actuated, Farnell # 1761633
PCB # 120368-1
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