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The frequency counter in Figure 2 has a range of 0 to 9 Hz and a resolution of 1 Hz. The schematic for this circuit is shown below:

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I'm trying to understand how this circuit works and how to increase the range of frequencies it can measure to 0 to 99 Hz with a resolution of 1 Hz.

A frequency of 0.5 Hz is connected to one input of the NAND gate and a frequency of 5 Hz from a signal generator is connected to the other input of the NAND gate. I know that the frequency output on the CD4029 is the same as the signal output of the signal generator, which is 5 Hz.

So does that mean the larger signal input on a NAND gate is always the output frequency of the NAND gate? And what is it that affects the range of frequencies that can be measured? I'm guessing that the BIN/DEC pin would have to be changed to binary but wouldn't that just limit the range to 15 Hz?

ocrdu
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Licentia
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    Welcome! Is this a coursework question? If so, best to include how you think this circuit is operating, and what progress you've made towards the goal. Clue: it's really best understood by thinking about the waveforms on nand gate u3a. – jonathanjo Oct 23 '22 at 00:19
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    What have you done to try to solve this yourself? Do you have a general idea of what you need to do? – Elliot Alderson Oct 23 '22 at 00:25
  • The datasheets do have the answer for you. – RussellH Oct 23 '22 at 00:49
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    Obviously you will need a counter that can count to at least 99. You can't do that with a single 4029 but maybe there is a way to multiple 4029's to increase the counting range. – ErikR Oct 23 '22 at 02:56
  • The resolution is given by the 0.5Hz signal, so this is what you want to keep. The range is given by the counter range, this is what you want to increase – Wheatley Oct 23 '22 at 07:29
  • That's a good start ... can I suggest you add a drawing of the waveforms into and out of the u3a NAND gate? And then draw them again when U6's f = 12 Hz, say. It's much easier to think about the dynamic behaviour looking at waveforms than at circuit diagrams. And much easier to change your circuit once you have full understanding of the current behaviour. Lastly, read the datasheets carefully: you don't need to understand every last word, but understanding what each section tells you is vital: then you can focus on the information you need. – jonathanjo Oct 23 '22 at 09:35
  • "I'm guessing that the BIN/DEC pin would have to be changed to binary but wouldn't that just limit the range to 15 Hz?" This is entirely correct: if you change to binary it only goes up to 15. – jonathanjo Oct 23 '22 at 10:08
  • A comment and a question: your diagram could do with being redrawn (see [good advice](https://electronics.stackexchange.com/q/28251)) -- it takes practice to make good diagrams, and for certain the legibility of them will affect your grades. Do you have to use specific parts, or are you free to choose whatever you want? Do you have a specific goal, or is it encouraged to exceed the goal? – jonathanjo Oct 23 '22 at 11:02
  • general remark: This would need exactly 5 components if done with a 1 € microcontroller (the microcontroller, a decoupling capacitor for it, the crystal, the two crystal load capacitors). This is a problem that microcontrollers really were made for: counting edges within a time period. Almost any microcontroller that exists has a timer unit that can do that without help of the CPU, but for your frequencies, even doing the counting in software would be a viable solution. – Marcus Müller Oct 23 '22 at 12:33
  • I know that I need to increase the CD4029s to increase the range to 99Hz and I'm thinking that I can use two CD4029 chips in decade mode along with eight LEDs on the Q outputs of each chip, but I'm confused with how to tie them together so that it takes the signal and outputs the frequency in binary to the 4 LEDs on the Q outputs of each chip. – Licentia Oct 23 '22 at 16:05

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