+ Post New Thread
Results 1 to 14 of 14

7th June 2012, 17:49 #1
 Join Date
 Jun 2012
 Posts
 6
 Helped
 0 / 0
 Points
 194
 Level
 2
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.

8th June 2012, 01:21 #2
 Join Date
 Feb 2011
 Location
 Oceanside, CA, USA
 Posts
 84
 Helped
 37 / 37
 Points
 1,814
 Level
 9
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
1 members found this post helpful.

Advertisement

8th June 2012, 16:12 #3
 Join Date
 Jun 2012
 Posts
 6
 Helped
 0 / 0
 Points
 194
 Level
 2
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.

8th June 2012, 16:41 #4
 Join Date
 Feb 2008
 Location
 Romania
 Posts
 1,874
 Helped
 1049 / 1049
 Points
 37,620
 Level
 47
Re: Digital Frequency meter  Circuit desing
@bencassar;
Have you considered using a microcontroller?
Here are some ideas:
http://www.qsl.net/dl4yhf/freq_count...q_counter.html
http://www.bestmicrocontrollerproj...ycounter.html
http://www.qsl.net/zl1bpu/MICRO/COUNTER/CNTR.htm
https://www.edaboard.com/thread246772.html
http://hem.passagen.se/communication/frcpll.html
http://www.linuxfocus.org/English/Se...ticle253.shtml
http://www.circuitvalley.com/2011/07...rcounter.html
http://www.qrz.ru/schemes/contribute...h2/ch2_eng.pdf
http://www.myplace.nu/avr/countermeasures/index.htm
http://www.webx.dk/oz2cpu/radios/counter.htm
1 members found this post helpful.

8th June 2012, 20:07 #5
 Join Date
 Jun 2012
 Posts
 6
 Helped
 0 / 0
 Points
 194
 Level
 2
Re: Digital Frequency meter  Circuit desing
I have to design this using digital electronics only. Thanks though :)

9th June 2012, 01:26 #6
 Join Date
 Feb 2008
 Location
 Romania
 Posts
 1,874
 Helped
 1049 / 1049
 Points
 37,620
 Level
 47
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 frequencycounter 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://makearadio.com/pastglories/counter1975.php
http://www.qsl.net/va3iul/Homebrew_R...nter_G0UPL.gif
http://www.schematicx.com/schematic/...rcuitdiagram/
http://www.hamradio.in/circuits/fcount.php
1 members found this post helpful.

Advertisement

9th June 2012, 05:13 #7
 Join Date
 Apr 2011
 Location
 Minneapolis, Minnesota, USA
 Posts
 12,949
 Helped
 2580 / 2580
 Points
 52,942
 Level
 56
Re: Digital Frequency meter  Circuit desing
I used two MC14553 (also known as 4553) to make my 6digit 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.

9th June 2012, 10:14 #8
 Join Date
 Jun 2012
 Posts
 6
 Helped
 0 / 0
 Points
 194
 Level
 2

9th June 2012, 11:23 #9
 Join Date
 Feb 2008
 Location
 Romania
 Posts
 1,874
 Helped
 1049 / 1049
 Points
 37,620
 Level
 47
Re: Digital Frequency meter  Circuit desing
Yes, that's OK.
   Updated   
Divide by 1000
1 members found this post helpful.

9th June 2012, 18:54 #10
 Join Date
 Feb 2008
 Location
 Romania
 Posts
 1,874
 Helped
 1049 / 1049
 Points
 37,620
 Level
 47
Re: Digital Frequency meter  Circuit desing
A fourdigit frequency counter built from TTLseries 7493/7490 integrated circuits. This circuit can be easily expanded to 67 digits.
1 members found this post helpful.

Advertisement

10th June 2012, 21:28 #11
 Join Date
 Jun 2012
 Posts
 6
 Helped
 0 / 0
 Points
 194
 Level
 2
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 :)

12th June 2012, 23:15 #12
 Join Date
 Feb 2008
 Location
 Romania
 Posts
 1,874
 Helped
 1049 / 1049
 Points
 37,620
 Level
 47
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 easytouse schematic editor.
1 members found this post helpful.

13th June 2012, 14:21 #13
Re: Digital Frequency meter  Circuit desing

13th June 2012, 18:20 #14
 Join Date
 Jun 2012
 Posts
 6
 Helped
 0 / 0
 Points
 194
 Level
 2
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) :)
+ Post New Thread
Please login