On 25/01/2025 14:02, Jeremy Elson wrote:

Call me fussy, but that looks like just a limited version of the
incoming Sine signal.   50/60Hz in, 50/60 Hz out.

A "Zero Crossing" detector would send out narrow pulses (at CMOS/TTL
levels) as the incoming signal crosses the Zero Voltage level,
traversing from + to -, as well as - to +.   But in both cases, it would
be the same polarity output signal.  But at twice the frequency of the
incoming AC power waveform.

There are plenty of tried and tested circuits for that provide that
function, easily found online.

Dave G8KBV.

--
Created on and sent from a Unix like PC running and using open source software:

https://dextrel.net/dextrel-start-page/design-ideas-2/mains-zero-crossing-detector

-=Bryan=-

From: Dave B via time-nuts time-nuts@lists.febo.com
Sent: January 26, 2025 2:14 AM
To: time-nuts@lists.febo.com time-nuts@lists.febo.com
Cc: Dave B g8kbvdave@googlemail.com
Subject: [time-nuts] Re: Now available: Zero-crossing detector ...
 
On 25/01/2025 14:02, Jeremy Elson wrote:

Call me fussy, but that looks like just a limited version of the
incoming Sine signal.   50/60Hz in, 50/60 Hz out.

A "Zero Crossing" detector would send out narrow pulses (at CMOS/TTL
levels) as the incoming signal crosses the Zero Voltage level,
traversing from + to -, as well as - to +.   But in both cases, it would
be the same polarity output signal.  But at twice the frequency of the
incoming AC power waveform.

There are plenty of tried and tested circuits for that provide that
function, easily found online.

Dave G8KBV.

--
Created on and sent from a Unix like PC running and using open source software:

time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com

hi,

this particular one is surprising: it starts the pulse before the zero
crossing itself. How accurate is that?

Sebastien

On 27/01/2025 17:22, Bryan _ via time-nuts wrote:

Yowsa, that is a good point, didn't even pick that up. Waiting for a opto to come in and will check myself on a scope. Suspect the design is such that it doesn't really matter on the exact timing of the cross, just that it occurs and would be consistent, probably not suitable for the of the original poster.

-=Bryan=-

From: Sebastien F4GRX via time-nuts time-nuts@lists.febo.com
Sent: January 28, 2025 2:43 AM
To: time-nuts@lists.febo.com time-nuts@lists.febo.com
Cc: Sebastien F4GRX f4grx@f4grx.net
Subject: [time-nuts] Re: Now available: Zero-crossing detector ...

hi,

this particular one is surprising: it starts the pulse before the zero
crossing itself. How accurate is that?

Sebastien

On 27/01/2025 17:22, Bryan _ via time-nuts wrote:

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The MCP6561 has built-in hysteresis, so the zero cross will be a window
around the real zero cross.

On Thu, Jan 30, 2025 at 8:41 PM Bryan _ via time-nuts <
time-nuts@lists.febo.com> wrote:

Hi,

then it means that the pulse timing will depend on the mains voltage
rate of change, which will be inaccurate if there are harmonics, or
noise/data signals near the zero crossing.

You would need some stringent mains frequency bandpass filtering to get
rid of most of that.

Numbers from your experiment will be interesting.

Sebastien

On 30/01/2025 19:34, Bryan _ via time-nuts wrote:

Hi

If you really want to dig into this, go back into the archives and look for “Colins limiter”. There is a lot of “trouble” that comes in when trying to get an accurate estimate of a slow moving edge. It normally gets a deep dive for things like ADEV testing when a beat note is being used.

Given how dirt cheap MCU’s with ADC’s on them are these days, there are a lot of options for doing “something fancy” ( = digital filtering / signal processing) with a 50 or 60Hz power line signal. Sounds like a great rabbit hole to spend a few years wandering down :) :).

Yes, one could ask “how good is good enough?”. Since this is Time Nuts …. there likely will be a wide range of answers to that question.

Bob

BTW the folks at RCA had a zero-crossing detector the CA3058, CA3059 that was available in 1982.  It was intended to provide a switching signal for a Triac.  I am not sure if it is still available, but I would imagine that if not there are other manufacturers that make a similar circuit.

Mike Bafaro

-----Original Message-----
From: Bob Camp via time-nuts time-nuts@lists.febo.com
Sent: Friday, January 31, 2025 8:40 AM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: Bob Camp kb8tq@n1k.org
Subject: [time-nuts] Re: Now available: Zero-crossing detector ...

Hi

If you really want to dig into this, go back into the archives and look for “Colins limiter”. There is a lot of “trouble” that comes in when trying to get an accurate estimate of a slow moving edge. It normally gets a deep dive for things like ADEV testing when a beat note is being used.

Given how dirt cheap MCU’s with ADC’s on them are these days, there are a lot of options for doing “something fancy” ( = digital filtering / signal processing) with a 50 or 60Hz power line signal. Sounds like a great rabbit hole to spend a few years wandering down :) :).

Yes, one could ask “how good is good enough?”. Since this is Time Nuts …. there likely will be a wide range of answers to that question.

Bob

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These days one would use something like a AMC23C10 from Texas Instruments.

--

Ruben

 
Those parts are fairly simple - they're a bridge with some form of limiter (probably diode clamps) and a threshold circuit.
I would assume that you deal with transients by filtering in front of it. 

On Fri, 31 Jan 2025 10:27:01 -0600, Michael Bafaro via time-nuts time-nuts@lists.febo.com wrote:

BTW the folks at RCA had a zero-crossing detector the CA3058, CA3059 that was available in 1982. It was intended to provide a switching signal for a Triac. I am not sure if it is still available, but I would imagine that if not there are other manufacturers that make a similar circuit.

Mike Bafaro

-----Original Message-----
From: Bob Camp via time-nuts
Sent: Friday, January 31, 2025 8:40 AM
To: Discussion of precise time and frequency measurement
Cc: Bob Camp
Subject: [time-nuts] Re: Now available: Zero-crossing detector ...

Hi

If you really want to dig into this, go back into the archives and look for “Colins limiter”. There is a lot of “trouble” that comes in when trying to get an accurate estimate of a slow moving edge. It normally gets a deep dive for things like ADEV testing when a beat note is being used.

Given how dirt cheap MCU’s with ADC’s on them are these days, there are a lot of options for doing “something fancy” ( = digital filtering / signal processing) with a 50 or 60Hz power line signal. Sounds like a great rabbit hole to spend a few years wandering down :) :).

Yes, one could ask “how good is good enough?”. Since this is Time Nuts …. there likely will be a wide range of answers to that question.

Bob

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