Article
Week/Month Timer
Programmable for long periods
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.
Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD 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 the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
The use of our Gerber files is provided under a modified Creative Commons license. Creative Commons offers authors, scientists, educators and other creatives the freedom to handle their copyright in a more free way without losing their ownership.
PCB
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.
Component list
Resistors:
R1 = 10M?
R2 = 270k?
R3 = 100k?
R4,R5,R7 = 10k?
R6 = 3k?3
Capacitors:
C1,C2 = 22pF
C3,C4 = 10nF
C5 = 1µF 16V radial
C6,C8 = 100nF
C7 = 100µF 16V radial
Semiconductors:
D1 = LED, high-efficiency, 2 mA
D2 = 1N4001
IC1 = 4541
IC2,IC4 = 4040
IC5 = 4068
IC6 = 555C (CMOS version)
Miscellaneous:
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
R1 = 10M?
R2 = 270k?
R3 = 100k?
R4,R5,R7 = 10k?
R6 = 3k?3
Capacitors:
C1,C2 = 22pF
C3,C4 = 10nF
C5 = 1µF 16V radial
C6,C8 = 100nF
C7 = 100µF 16V radial
Semiconductors:
D1 = LED, high-efficiency, 2 mA
D2 = 1N4001
IC1 = 4541
IC2,IC4 = 4040
IC5 = 4068
IC6 = 555C (CMOS version)
Miscellaneous:
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
Discussion (0 comments)