About the article

Digital Alarm Clock

Based on a PIC micro

Although digital alarm clocks have been around for years, most of today’s off the shelf products suffer from serious design limitations. For example, many don’t keep track of weekdays and can only store one alarm time. High time for a home-brew design that does a better job.Off the shelf alarm clocks present a serious limitation if, for instance, you and your partner have different wake-up times or if you have to give or take medication at regular intervals. This limitation gets more serious if you want alarms to go off only on specific days of the week or only during work days. The time setting process on most clocks is also subject to improvement. In the majority of cases you adjust time by incrementing minutes and hours. If your clock is at, say, 06:15h and the correct time is 20:58h you need to keep a key pressed for quite some time and release it well before the desired hour/minute, switching to ‘slow’ setting. If not, you’re past the desired time and have to start all over again.
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R1, R11,R14-R45 = 1kOhm
R2...R10,R13 = 10kOhm
R12 = 2kOhm 2
C1,C2 = 22pF
C3,C4,C6-C10 = 100nF
C5 = 1000µF 16V radial
C11 = 1µF 16V radial
D1,D2 = LED, 3mm, red, low-current
D3 = 1N4001
D4 = 1N4148
T1 = BC547
IC1-IC4 = 74HCT164
IC5 = PIC16F84-04/p, programmed, order code 030096-41
IC6 = 7805
K1 = 2-way PCB terminal block, lead pitch 5mm
S1 = on/off switch
S2-S7 = miniature PCB mount pushbutton, type DTS65N
LD1-LD4 = LTS4301E (Lite-On)
BZ1 = 5VDC buzzer (active)
X1 = 4MHz quartz crystal
BT1 = 9V battery with and clip-on lead
PCB, available from The PCBShop
Disk, PIC source and hex (object) code files, order code 030096-11 or Free Download
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