Frequency counter and "reset" using 4029 chips

Discussion in 'General Electronics Chat' started by miguelpedroso, Oct 14, 2012.

  1. miguelpedroso

    Thread Starter New Member

    Aug 13, 2012
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    Hey guys!

    I'm bulding a frequency counter, using 7 segment displays, 4511 display drivers, and 4029 decade counters. Each terminal count of the counter is the clock of the "next" counter, pretty simple.

    Then I have a 1 Hz reference signal that I need to use to latch the 4511 output (to latch the displays) AND to reset the 4029 chips (the 4029 chips don't have a master reset, but I'm using an asynchronous paralel load of 0000 to "reset").

    Thing is I'm not being able to do this :/ I need to FIRST "unlatch" the 4511, then "latch" it again to store the frequency that was counted in the previous second, and finally "reset" de 4029 chips throught the asynchronous paralel load. (because if I do it at the same time, the displays will always show 0000)

    Thing is I'm trying to solve this issue for hours and still not being able to do this with flip flops or finding another solution. :/

    Guys do you have any idea?

    Thanks!
    Miguel
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    If you have some invertor available to make a simple rc oscillator or have some other clock source, you can use 74hc164 shift register to generate the sequence you need.
    The only problem is that you need the 1hz signal to be as short as the clock, so that each output is activated separately. This can be done with an edge detector, for which you need two D-latches and some gate.
     
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  3. timescope

    Member

    Dec 14, 2011
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    Divide the 1Hz reference by 2. The reference will then be H for 1 second allowing counting.
    You will then have another 1 second when it is L to insert your latch and reset pulses which you can generate with monostables or simple RC and gate circuits triggered by the falling edge of the reference.

    Timescope.
     
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  4. miguelpedroso

    Thread Starter New Member

    Aug 13, 2012
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    hey guys, thanks for your replies! I'm kinda confused. :/

    Well I'm generating the 1 hz signal using a crystal and a 4521 frequency divider.

    Now, as you said, diving 1 Hz by to gives me 0.5 Hz or 2 seconds, Now in the first second the displays are latched and the reset is low, so the counters are counting and the displays shows the "last frequency", then in the next second the reference signal goes down and I need to detect it and then I give a small RC pulse to the latch (so it latches the new value) and at the same time, I'll be trigging another small, but a little longer RC delay to trigger the counters "RESET").

    Have I understood you correctly?

    But if so, what happens during that 2nd second, where the "reference" is LOW? I latch the new value, I reset the counters, and it stays wainting there till the next HIGH, where it will beggin counting again?

    I'm also trying to get away from the 74164 solution because I need to build this very soon and I can't find a store that sells it.

    Again thanks a lot for your anwsers guys!
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    could you post the schematic of what you got so far?
     
  6. miguelpedroso

    Thread Starter New Member

    Aug 13, 2012
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    Sure thing!

    (I already made some attempts with some 4042 d latches, but as I was working on that for many hours without getting results I decided to clean the circuit and I took a little break so those schematics do not show my "attempts"). I'm simulating both clocks (the reference clock and the external clock: the one that will be measured) as logic switches in CircuitMaker.

    Thank you!
     
    Last edited: Oct 14, 2012
  7. timescope

    Member

    Dec 14, 2011
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    You are correct, one second is wasted latching the count then resetting the counter. What crystal frequency are you using with the 24 stage divider?. It may be possible to derive a better solution by gating outputs of the 4521.

    Timescope.
     
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  8. miguelpedroso

    Thread Starter New Member

    Aug 13, 2012
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    I think I'll be using a 4,194304MHZ crystal. At least the stores where I'll be getting the parts have it on stock.

    Thanks!
     
  9. MrChips

    Moderator

    Oct 2, 2009
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    drkblog and miguelpedroso like this.
  10. timescope

    Member

    Dec 14, 2011
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    This circuit should solve the problem. The 4511 latch is level controlled, H =latch, L = output follows data . The 4029 requires a positive pulse to load preset data (clear in your case) The Q23 output of the 4521 is 2Hz with your crystal. You will need one more gate for the input signal.

    Timescope
     
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  11. miguelpedroso

    Thread Starter New Member

    Aug 13, 2012
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    Thank you guys for your solutions! :)

    @timescope, I particulary like your solution. Just a thing, you mean Q21 is 2 Hertz, right? With that crystal, Q23 should be 0.5 Hertz, which is what we want here correct?

    I think your solution is really elegant but just a question, is there any diference between using the NAND gates or using single NOT gates to replace them, like stability or so?
     
  12. ScottWang

    Moderator

    Aug 23, 2012
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    I designed a 6 digits Frequency counter used many logic ICs, as 74HC14, 74LS74, CD4518, CD4511, if you just want to design a Frequency counter, and no other functions, then you no need to used Up/Down counter. just the up counter as CD4518.

    I set three time base, as 10S, 1Sec, 0.1Sec, so I can measured down to 0.1Hz(10S), 999.999 Khz , 9.99999 Mhz.

    And I added a 74HC390 to divided by 10, before the frequency into the counter, so I can expanding the measure range up to 60Mhz, and even more.
     
  13. takao21203

    Distinguished Member

    Apr 28, 2012
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    Some years ago I made a 2-digit LED display freq. counter based on 1x 16F54, and one AM adjustable coil (case looks like a small IF transformer). I used that adjustment instead of modifying the software.

    The frequency signal itself was routed to the timer input.

    Onboard I had a 18 MHz crystal OSC as well for calibration.

    Two pushbuttons were used to switch ranges (so it could be used from kHz upto 10s of MHz).

    It worked quite well. For calibration I switched into the highest range, and turned the slug until the display showed "18".
     
    Last edited: Oct 15, 2012
  14. ScottWang

    Moderator

    Aug 23, 2012
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    When the two digits get into my mind, I felt it's funny, because that I never saw a digits of frequency counter is so less, I saw the less one was three digits.

    Maybe I always like see the detail of frequency, as the Mhz or Khz till Hz of the unit.

    Sometimes, we don't need to know the detail, then this two digits F-counter will be nice, maybe I wll make one, and the parts is so less.
     
  15. miguelpedroso

    Thread Starter New Member

    Aug 13, 2012
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    I'll be building a full 6 digit one :) Well I already ordered the 4029 chips so I'll stick to them anyway. Frequency range will be 0-1Mhz, maybe I I also make another option and make it 10Hz-10Mhz, dividing the frequency by 10.

    By the way guys, I've always been curious, how could I implement, say, a 1Khz-1Ghz frequency counter. How could I prescale such high frequencies, without using these standart "low frequency" ttl/cmos chips?
     
  16. MrChips

    Moderator

    Oct 2, 2009
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    74F160 will count to 100MHz.
    Remember that you only need this for the first stage if you cascade as ripple counter.
     
  17. ScottWang

    Moderator

    Aug 23, 2012
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    I also thought about how to make a 500Mhz F-counter, but I can't find any easy way to do that, until now I only can make the frequency under 200Mhz, and I asked a friend whom have been worked in the instrument company, he said that the important chips of 500Mhz F-counter used, they designed their own functions and asked the IC manufacturer to make those ICs for them.

    So if you want to design a F-counter and the frequency is too high, that is not easy, if you have enough money, then you can buy the new one, otherwise then you can buy the second hand from EBAY.
     
  18. MrChips

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    Oct 2, 2009
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    ScottWang likes this.
  19. miguelpedroso

    Thread Starter New Member

    Aug 13, 2012
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    Oh thank you I din't know. Never heard of those series, they must cost a "fortune". And never found a store that had them.
     
  20. timescope

    Member

    Dec 14, 2011
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    Hello miguelpedroso,

    0.5 Hz is correct, sorry for the error. You can use any CMOS B series inverters that are available. Sorry for the late reply.

    Timescope

    ps. Another nice counter ic is MC14553. It is a complete 3 digit counter and very easy to use.
     
    Last edited: Oct 15, 2012
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