I'm an amateur analogue circuit lover and online learner person. I'm building a system which starts every four hours and closes itself. My system is ready but needs a signal to start. I've been looking for delays on timers. I used the NE555 astable mod accuracy was bad. I found the CD4060 recommendation from ChatGPT. But I have still a problem I calculated 100 uF capacitor 3995 ohm rx resistor and 10 kΩ rs resistor and it's not working. I can create 1 Hz clock signal with IC's but I need to break counting at 14400 pulse. I'm open to new solutions and new IC recommendations except microcontrollers and Arduino.
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\$\begingroup\$ Have a look at this answer, which uses a timer-counter IC to produce a 1 hour delay. Might be a start. \$\endgroup\$TonyM– TonyM2024-09-18 11:08:30 +00:00Commented Sep 18, 2024 at 11:08
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\$\begingroup\$ Linear/Analog devices TimerBlox? \$\endgroup\$winny– winny2024-09-18 11:13:19 +00:00Commented Sep 18, 2024 at 11:13
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2\$\begingroup\$ It's just silly to exclude microcontrollers. You could use a series of Decatrons I guess. \$\endgroup\$Spehro 'speff' Pefhany– Spehro 'speff' Pefhany2024-09-18 11:33:09 +00:00Commented Sep 18, 2024 at 11:33
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1\$\begingroup\$ @HakanGözübüyük A year is 8760 hours, so one hour per 8760 hours requires accuracy at least 0.0114% or 114 PPM. You can't achieve that with RC components. How much money, time, and effort you can put in to not use MCUs and crystals? I guess crystal oscillator modules and clock dividers might do th trick. \$\endgroup\$Justme– Justme2024-09-18 12:08:42 +00:00Commented Sep 18, 2024 at 12:08
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1\$\begingroup\$ @TonyM Yes, there are many common applications where creating and maintaining a 12-line program is prohibitively expensive. That's why we see so many designs using only logic chips and so few microcontrollers. \$\endgroup\$Spehro 'speff' Pefhany– Spehro 'speff' Pefhany2024-09-18 16:00:30 +00:00Commented Sep 18, 2024 at 16:00
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3 Answers
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The solution has three basic components.
A crystal oscillator. The lower the frequency, the better; it reduces the number of divider ICs.
If you start with a 32 kHz watch crystal, then you need a 29-bit binary divider. This has to be spread out over multiple ICs, and there are hundreds of different combinations of CMOS counters/dividers that can do this. A common starting point is to combine the oscillator and the first 14 bits of dividing into a single CD4060. Another option (if you can find one) is the CD4521, which is an oscillator plus a 24-bit divider. With this part, you need only one additional divider IC.
Gating to decode 14400 seconds and produce an appropriate output signal.
An alternate approach is to use a 24-hour lamp timer, set to turn a device on and off 6 times per day. Instead of a lamp, plug in a 5 V USB charger. This will produce a timing edge once every four hours, with excellent long-term accuracy and no adjustments. The charger output can power a monostable circuit to produce a short, clean pulse, or power some other small circuit or device.
I mention a 5 V wall wart only because they are so common and low cost. Any power source, large or small, can be used for whatever your application is. Depending on what your "system" is, it could power all of it; turning the whole thing on and off rather than just triggering it.
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For your desired ~100ppm accuracy you're better off with a crystal, eg. 32,768Hz tuning fork type.
You could do it with three ICs- a 4060 oscillator/divide by 16,384 which would give you 2Hz, a 4017 to divide by 10 (0.2Hz) and a 4059 set to divide by 2880. The latter is still made, but like many such CMOS chips of that ilk, edging toward obsolescence (DIP is discontinued, only SMT)
If you want to trim the accuracy, add a variable capacitor to the crystal oscillator circuit, take the signal off of Q4 of the 4060 and adjust it to exactly 2048Hz using a reciprocal type frequency counter.
answered Sep 18, 2024 at 12:25
Spehro 'speff' Pefhany
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\$\begingroup\$ Thank you for answering its totally clear and simple solution but I have a problem and that is 4059 not foundable in my country and it's expensive instead 4059 can I use any other IC \$\endgroup\$Hakan Gözübüyük– Hakan Gözübüyük2024-09-18 12:37:55 +00:00Commented Sep 18, 2024 at 12:37
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\$\begingroup\$ Sure, but it's more complicated to design and more complicated to build. \$\endgroup\$Spehro 'speff' Pefhany– Spehro 'speff' Pefhany2024-09-18 12:42:47 +00:00Commented Sep 18, 2024 at 12:42
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You can cascade the 4060 or its relative the 4040. I have done this last century and it is cheap and reliable. Downsides are PCB real estate and lack of flexability. I have seen the 4521 used but have not used it myself. There are also electric clock divider chips which have a big division ratio and often run on 1.5 VDC. Any scheme with a big division ratio will keep the proposed RC oscillator away from large resistor values and big caps so you do not have to worry about leakage or electrolytic caps. This means that any RC oscillator will be reasonably stable.
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\$\begingroup\$ Idea is good but I don’t know how can I made it without circuit diagram \$\endgroup\$Hakan Gözübüyük– Hakan Gözübüyük2024-09-18 12:09:18 +00:00Commented Sep 18, 2024 at 12:09