Digital Chronometer help

Discussion in 'General Electronics Chat' started by oki, Sep 13, 2013.

  1. oki

    Thread Starter New Member

    Sep 13, 2013
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    Hello everyone,

    I' need a digital chronometer circuit design, I have used a few chronometer and counter circuits in university, but I do not have those resources now. Therefore, I need a digital chronometer circuit schematic which has 6 digits and 0.01 second sensitivity.

    If someone is able to help me to find. I'd be sooo happy.

    By the way, I've found lots of circuit design on internet but I dont trust them..

    Thank you.
     
  2. BillB3857

    Senior Member

    Feb 28, 2009
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  3. oki

    Thread Starter New Member

    Sep 13, 2013
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    Thank you for the answer. In fact, I have some measurement devices which can measure temperature,voltage,current,force etc. I need a digital chronometer in order to use it with that sensor devices. I mean, It should be connected to the sensors. Not an external devices like in that link. I just want to have a circuit diagram. That might be helpful for me.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Possibly look at a PicMicro it will do the timing and hook into sensors and also a single line LCD display.
    A 32.768Khz clock crystal input into the T1 inputs allows the Timer 1 to be set up as a clock.
    Max.
     
  5. #12

    Expert

    Nov 30, 2010
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  6. WBahn

    Moderator

    Mar 31, 2012
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    So.... you don't trust designs you find on the internet, so you come to an internet forum looking for a design?
     
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  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I like to use old $5 digital watches with stopwatch functions. I pull the back off, tap into the start/stop feature and clock pulse and use a Microcontroller to start/stop. I get a display but also the clock pulse that is accurate enough (in most cases). Basically a free 3276800hz crystal and 0.01 sec accuracy.

    Old Casio seem to be the most accessible.
     
  8. WBahn

    Moderator

    Mar 31, 2012
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    I thought these were pretty universally 32768Hz crystals.
     
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The 1990s watches with 0.01 sec stopwatches have a faster crystal. Some have two crystals - I guess to save power when the stopwatch is not needed. The newer watches are too closed up to do anything with.
     
  10. WBahn

    Moderator

    Mar 31, 2012
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    I take you at your word -- I certainly don't know. I don't see why they would need a faster crystal. The 0.01s "accuracy" is totalyl bogus to begin with because the uncertainty in when you press either the start or the stop is far more than that.

    But even if this isn't the case, a 32.768kHz oscillator provides over 327 clock pulses in 0.01s. Even if the processor is dividing that down by a factor of 4 to get its instruction clock (and I don't know whether it is or not) that is still over 80 instruction cycles per event. I don't see the case for using a faster oscillator that is going to consume considerably more power from this dinkly coin cell battery that you want to last a couple of years in a circuit that you are going to make millions of and so shaving even a fraction of a cent from the BOM is going to add thousands of dollars to your bottom line.

    If they did go that route, it would actually be informative to understand the reasoning behind it.
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I never thought about it much. I just assumed the pulse for the 0.01 sec increment came from a faster crystal. I just tap in and find a 100 hz pulse.
     
  12. oki

    Thread Starter New Member

    Sep 13, 2013
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    Yes, what's the problem sir? I'm not an electronics engineer, I do not know which one is correct and proper for my purpose therefore I need to ask it to someone who know it well. I just want to have a completed and ready to use, design.
     
  13. WBahn

    Moderator

    Mar 31, 2012
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    1) If you want a completed and ready to use design, you need to provide a lot more information about what your requirements and interface is.

    You were given a link based on your initial post and then you basically said, "Nah, not what I'm looking for. It has to connect directly to my sensors." So now you've added something to the requirement that you didn't mention initially. Are we headed down a road where everytime someone suggests something you pull out yet another tidbit of information that makes that suggestion worthless?

    You still haven't given any indication of that connecting directly to your sensors even means. What does it mean to connect a chronometer to a temperature sensor? What is supposed to happen? What is the physical and electrical interface?

    2) You are basically asking strangers to do work for you for free. Most of us here will bend over backwards to help someone learn electronics and do something on their own, but getting people to just be a one-stop free design service is a lot more problematic.
     
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