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Week/Month Timer

Programmable for long periods

Week/Month Timer
As opposed to most timer circuits, this month’s Mini Project is intended for very long periods. A switchable divider chain using two 4040 counter ICs allows periods of up to 194 days (yes that’s 6 months) to be timed with great accuracy. Almost any other period shorter than the maximum may be set up, and all without a microcontroller or indeed any sort of exotic component!It started out as a relatively simple project — a timer to remind us (and friends) to take our wheelie bins out ready for collection once a week (or month). The original intention was to make the timer drive a voice/record playback module programmed with a snappy message. However, for the purpose of this Mini Project, such an extension was deemed too complicated, so a rather simpler ‘time-out’ warning device was chosen, although it is still possible to hook up a voice module if you want to.
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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.

Extra info, Update
One of our readers kindly informed us that a number of ICs type CD4068 or HCF4068, including those manufactured by Philips Semiconductors, have an additional output on pin 1. The ST Microelectronics HCF4068 used in our prototype did have such an output.Part of the rule mentioned under Step 2 in the section ‘How to set the period’ is incorrect and should be amended to read: ‘… the first number that’s smaller than or equal to the above value.’ This rule is, in fact, applied in the example that follows.
R1 = 10M?
R2 = 270k?
R3 = 100k?
R4,R5,R7 = 10k?
R6 = 3k?3
C1,C2 = 22pF
C3,C4 = 10nF
C5 = 1µF 16V radial
C6,C8 = 100nF
C7 = 100µF 16V radial
D1 = LED, high-efficiency, 2 mA
D2 = 1N4001
IC1 = 4541
IC2,IC4 = 4040
IC5 = 4068
IC6 = 555C (CMOS version)
JP1 = jumper
K1,K2 = 12-way SIL pinheader
K3 = 8-way SIL pinheader
K4,K5 = 4-way SIL pinheader
S1 = pushbutton, 1 make contact
X1 = 32.768kHz quartz crystal
9-V PP3 (6R22) battery with clipon wires
PCB, available from The PCBShop
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