[time-nuts] TBolt: UTC PPS

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Mar 29 23:06:47 UTC 2010


Use a JK flip flop to divide by 2.
During insertion of the leapsecond take J+K to zero to disable toggling 
of the FF.
To delete leap second you could try inserting an extra clock pulse 
halfway between a apair of seconds ticks.

If the clock cant cope with the above scheme you may need to use a DDS 
or equivalent to create either 59, 60 or 61 pulses for a minute 
depending if one needs to delete a leap second, increment the clock at 
the normal rate ,add a leapsecond over 1 minute.

Bruce

Neville Michie wrote:
> The most available analogue dial for PPS clocks is the common quartz 
> clock movement.
> You can leave the unpowered quartz unit in circuit and just connect to 
> the coil.
> The drive is a 5V square wave signal of 0.5 Hz coupled through an 
> electrolytic capacitor
> in the order of 10 - 100mfd. A series resistor of a few hundred ohms 
> may help.
> Each make of clock may need different values to work best, the drive 
> is the alternating
> positive and negative impulse. The original unit may have had a pulse 
> about 20ms long,
> but the square wave drive gives a longer tail. Over-driving is just as 
> bad as under-driving,
> to work well you must optimise the capacitor and resistor.
> It is simple to divide the PPS to the square wave, but what is needed 
> is a simple/surefire
> method of adding/removing the leap seconds. Preferably one that works 
> automatically.
> Any ideas?
>
> Neville Michie
>
>
> On 30/03/2010, at 9:02 AM, Hal Murray wrote:
>
>>
>> tvb at LeapSecond.com said:
>>> The words "insert a pulse" is what causes the confusion in 
>>> conjunction with
>>> leap seconds. There is no extra or missing pulse; no double pulse, 
>>> no early
>>> or delayed pulse.
>>
>>> The 1PPS output continues to give a pulse at a 1 Hz rate regardless 
>>> if there
>>> is leap second or not. There is never any ambiguity with TAI or UTC 
>>> with
>>> respect to the pulses themselves.
>>
>> Right.
>>
>> I was commenting about the sub-thread that was expecting an extra 
>> pulse so a
>> mechanical clock would stay in sync over a leap second event.
>>
>> Since what's needed is removing a pulse (to allow for the leap second),
>> rather than inserting a pulse, I still like the idea of poking a 
>> finger on
>> the right place in the clock to gum up the works for one tick.
>>
>>
>> -- 
>> These are my opinions, not necessarily my employer's.  I hate spam.
>>
>>
>>
>>
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