[time-nuts] Driving clocks from 1pps

Didier Juges didier at cox.net
Fri Sep 5 00:24:12 EDT 2008


 

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Tom Van Baak
> Sent: Thursday, September 04, 2008 11:17 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Driving clocks from 1pps
> 
> >> 50% duty cycle is way overkill, perhaps even harmful. In 
> the 'scope 
> >> traces below you can see the IC generates just 50 ms 
> biphase pulses 
> >> every second. That's 1/20, or 5% duty cycle.
> > 
> > No Tom, you misunderstand.  The 50% duty cycle pulse provides the 
> > rising and falling edges.  The small capacitor 
> differentiates that to 
> > produce a positive going, or a negative going pulse to make 
> the motor 
> > move.
> > 
> > -Chuck Harris
> 
> Ah, I see now. It's a 0.5 Hz square wave. Cool. Yes, that 
> looks like it might work. Has someone tried this on a quartz 
> clock stepper motor to make sure you reliably get sufficient impulse?
> I wonder why no commercial clocks use this trick.
> 
> /tvb
> 
> 

The capacitor gets too large for a commercial watch or clock, silicon is
cheaper.

Didier KO4BB





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