Generating 1Hz frequency

Discussion in 'General Electronics Chat' started by RRITESH KAKKAR, Jun 30, 2015.

  1. RRITESH KAKKAR

    Thread Starter Senior Member

    Jun 29, 2010
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    Hello Guys,
    I am Electronic project of Clock with 1 Hz frequency to make Clock on Led 7 segment Display.
    will 555 is better in astable mode or 4060??
    here is similar video of projects.
     
  2. ScottWang

    Moderator

    Aug 23, 2012
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    1Hz time base - using CD4060, CD4013, 32768hz crystal.
    I was used this circuit for a long time.

    [​IMG]
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    555 timer works with an RC network and relies on the accuracy of resistor and capacitor values. Once you tune it to exactly to 1 Hz, it will be susceptible to changes in temperature, humidity, changes over time and likely minor changes in voltage to the 555.

    A crystal is much more stable and better for clocks.
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Battery operated wall/desk clocks have an internal chip that generates two 2 second pulses 180° out of phase. By adding these pulses you get a pulse every second. Cheap ands easy to get 1-second pulses. Gutting a clock you find a small PCB with battery contacts and two wires (output 1 and output 2) to the clock motor.
    1 Second Clock.gif

    Ken
     
    RichardO and AnalogKid like this.
  5. crutschow

    Expert

    Mar 14, 2008
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    I agree with GopherT.
    For a clock application use Scott's CD4060 circuit with a crystal.
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    As I use mostly time signal controlled clocks, it becomes obvious that the just "quartz" variety can drift by as much as a few minute a week.

    One of the clocks is analogue, so it would be easy as you suggest to tap the pulses that step the movement - but the one I have steps in 1/3 minute increments.

    Another problem - the radio controlled variety are still crystal controlled, they just read for the correct time once per hour and make whatever correction is needed for the display.

    At least one of the magazines available in the UK has published a project for a 1Hz GPS timebase in the past year or three.
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The cheap quartz crystals from China are not 32768Hz and need a lot of coaxing to get there - and therefore, they do not stay there over time or over temperature variation, ...

    I have one CD4060 clock that is pretty darn good - 1 to 2 minutes per month.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    The little watch crystals are actually quite good for what they are - but it could well depend on what part of China they came from.

    The "quartz" clock I mentioned in my post was manufactured in Germany, but the crystal probably still came from China.

    In the UK we have (or possibly had!) a radio station on 198kHz with carrier locked to the NPL frequency standard, over the decades various electronics and amateur radio magazines have published PLL designs to convert this standard locked frequency to more convenient numbers for the test bench.

    IIRC: the US has one at 10MHz, which would be dead easy to divide down with a neat row of decade counters.
     
  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The little watch crystals are much better when they are attached to an organically-fueled, biologically controlled, temperature-stabilizing conduction plate - the wrist. I get 1/2 minute/year from mine.

    ak
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    For me - any cheap brand watch from any shop anywhere, always gained about 4 - 5 minutes and then stabilised.

    For a while it was convenient to just leave it like that and be 4 - 5 minutes early for those important appointments, but I started taking the error into account and ending up late instead.

    Then I bought a radio time signal watch, so its always what time it says.

    When I bought that, it would have been £60, but I paid the extra £20 for the one with stainless bracelet, recently saw the same watch advertised at £135.

    A few years back one of the discount chains had a very basic time signal watch for £15, I bought one as a spare - maybe hospital appointments where I have to leave any metal objects in the changing room where security isn't so good.
     
    Last edited: Jun 30, 2015
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I meant the cheap-cheap ones on ebay - 10 pcs for $1. Biggest waste of time ever - pun intended. For the few I use, I will buy mine from a supplier that can give me a part number and datasheet.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    Well, if you don't even know what part of China they came from - what do you expect!
     
  13. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    And besides, the 1 second "leap second" to be implemented at 8pm EDT will really screw up my accuracy.
     
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