# Digital Frequency meter -- Circuit desing

1. ## Digital Frequency meter -- Circuit desing

I am trying to build a digital frequency meter ranging from 9 Hz to 999Khz. I am trying to use a set of decade counters interfaced with a 7 segment driver and decoder. Can anybody help me with this idea because i am finding it petty hard to put it to work on a digital circuit.

2. ## Re: Digital Frequency meter -- Circuit desing

Ok, let's try it the brute force way. You'll need 6 counters, 6 decoders/drivers, and a 6 digit, 7 segment display or 6 individual displays. Add a 1 Hz gate clock, some latches between the counters and decoders/drivers and maybe an input amplifier (depending on your source).

Now for the next level of details. The 6 counters need to be hooked together using their carry bits to form a single 6 digit counter. Depending on what kind of counters (ripple or parallel) the carry bits will need to be hooked up differently. There are diagrams on the net for that. The 1Hz can be derived from a watch crystal and a couple of cmos logic inverters to make an 32768Hz oscillator. Divide that by 2^15 to get 1Hz. That 1Hz clock will need some additional logic to create signals to latch the count and clear the counters on each 1Hz cycle.

Some other notes. The decoder/drivers need to match the display type, common cathode or common anode and you'll need current limiting resistors. You'll need to be consistant about the logic levels if you use different logic families require HC, HCT, etc. And you'll need some sort of power supply.

That's about it for the gross details. I hope I have provided a useful overview and some direction. There are other approaches, more integrated ICs, using microprocessors for display and control, increased or decreased resolution but without more specific design requirements the book is wide open.

Ray

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3. ## Re: Digital Frequency meter -- Circuit desing

Thank you very much ray, i have managed to create that working circuit counting from 1hz to 999hz, i am trying to implement your idea by adding a prescaler on the input and divide the frequency by 10, 100 and 100. By doing so the result will be on a 3 digit 7 segment with freq selection and a decimal point instead of 6 digits. Have you got any idea of some frequency dividing ic? I was going to use the 7493 ad a divide by 10 and Cascade 3 of them.

4. ## Re: Digital Frequency meter -- Circuit desing

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5. ## Re: Digital Frequency meter -- Circuit desing

I have to design this using digital electronics only. Thanks though :)

6. ## Re: Digital Frequency meter -- Circuit desing

First you need to choose how many digits to use for display. Secondly decide what circuits type you may use, TTL, CMOS.
Thirdly check for the available xtal frequencies in order to find suitable counters to create the time reference circuit.
A frequency-counter block diagram:

Just for your information some example here:
http://www.cqham.ru/dfc.html
http://www.seekic.com/circuit_diagra...Y_COUNTER.html
http://www.qsl.net/va3iul/Homebrew_R...nter_G0UPL.gif
http://www.schematicx.com/schematic/...rcuit-diagram/

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7. ## Re: Digital Frequency meter -- Circuit desing

I used two MC14553 (also known as 4553) to make my 6-digit frequency counter. It counts from 1 to 999,999.

Each IC is a 3 digit counter with latch. You attach a 4511 or 4543, depending on what display you are driving.

It can multiplex three digits, to save power.

8. ## Re: Digital Frequency meter -- Circuit desing

I need to cascade the 7493 to create the divide by 10 precsaler, but its not working, attached is an image of how im wiring it.

Am i doing this right for a divide by 10 ?

9. ## Re: Digital Frequency meter -- Circuit desing

Yes, that's OK.

- - - Updated - - -

Divide by 1000

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10. ## Re: Digital Frequency meter -- Circuit desing

A four-digit frequency counter built from TTL-series 7493/7490 integrated circuits. This circuit can be easily expanded to 6-7 digits.

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11. ## Re: Digital Frequency meter -- Circuit desing

What simulation software are you using ? I use proteus and its pretty much the best. Thank you very much for your help :)

12. ## Re: Digital Frequency meter -- Circuit desing

That’s a very simple program, an old version of TINA Design Suite. I have installed this to be used as a easy-to-use schematic editor.

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14. ## Re: Digital Frequency meter -- Circuit desing

Thank you for all the help, i managed to build the circuit with ranging switches 3 segments and all, in real life on a breadboard. (Y) :)

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