There is no need for a transformer here. Yes you want isolation but
an optocoupler in a 8-pin DIP package can do that job better.
You can reduce the 120 VAC volts down to anything you like by clipping
it with diodes then send the clipped AC to the coupler and
The usual method if edge dietitian
Actually, the core saturation depends on how much voltage is applied
at a given frequency. Most power transformers are run partly into
saturation at rated line, to get the most from the copper and iron
available, in exchange for heat and less efficiency. The magnetizing
current and losses will
On Sat, 20 Dec 2014 18:31:29 -0500
"Mike Garvey" wrote:
> From a Time-Nut perspective, isn't phase/frequency of the (nominal)
> 60 Hz all we'd be interested in? Phase is best measured at a zero
> crossing as this is the (only) phase measurement point which is
> independent of amplitude.
> Mike
On Sun, 21 Dec 2014 17:37:07 -0500
Charles Steinmetz wrote:
> Ed wrote:
>
> >It seems to me that a low voltage secondary should be OK by using a
> >fast comparator IC rather than a transistor to decide - the gain of
> >the IC allows for much smaller detection levels, so the equivalent
> >zero
Chuck wrote:
Transformers, such as are in wall warts, etc..., are wound
in a way that is pretty good for 50Hz/60Hz operation, but have
had nothing intentionally done to normalize operation at any
other frequency. Nor have they had anything done to improve
the fidelity of the signal they pass.
Ed wrote:
It seems to me that a low voltage secondary should be OK by using a
fast comparator IC rather than a transistor to decide - the gain of
the IC allows for much smaller detection levels, so the equivalent
zero-crossing velocity could be the same. An IC tripping in a 10 mV
band should
Didier wrote:
A commend regarding your ZCD. You propose to use a dual 120V primary
transformer to generate the isolated 120V AC needed by your circuit.
Unless specifically designed for that purpose, the isolation between the
two 120V primaries of a common transformer is probably not as good as t
It seems to me that a low voltage secondary should be OK by using a
fast comparator IC rather than a transistor to decide - the gain of
the IC allows for much smaller detection levels, so the equivalent
zero-crossing velocity could be the same. An IC tripping in a 10 mV
band should provide the
Hi Charles,
I have a question about the accuracy of your scheme, given
transient effects.
Transformers, such as are in wall warts, etc..., are wound
in a way that is pretty good for 50Hz/60Hz operation, but have
had nothing intentionally done to normalize operation at any
other frequency. Nor h
Charles,
A commend regarding your ZCD. You propose to use a dual 120V primary
transformer to generate the isolated 120V AC needed by your circuit.
Unless specifically designed for that purpose, the isolation between the
two 120V primaries of a common transformer is probably not as good as the
isol
Mike wrote:
From a Time-Nut perspective, isn't phase/frequency of the (nominal) 60 Hz
all we'd be interested in? Phase is best measured at a zero crossing as
this is the (only) phase measurement point which is independent of
amplitude.
That is the primary interest (as I understand it -- I am
ime-nuts-boun...@febo.com] On Behalf Of Charles
Steinmetz
Sent: Saturday, December 20, 2014 4:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Simple AC mains zero-cross detector
Magnus wrote:
>So, I do not completely agree that a through-zero measurement
Magnus wrote:
So, I do not completely agree that a through-zero measurement with a
TIC has all the information
No, a series of time-stamped zero crossings doesn't have all of the
information in the original signal, and a small glitch that occurs
during the middle of a cycle (far away from a
Charles,
On 12/20/2014 09:24 AM, Charles Steinmetz wrote:
Gary wrote:
I try to minimize dangerous voltages. Anyway, the filtering reduces the
slew, so you can't have it both ways.
Starting with 120v gives you 10x the slew rate that starting with 12v
does, whatever filtering you use.
If by
d read.
See http://www.insidegnss.com/node/4281
Mike
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray
Sent: Wednesday, December 17, 2014 3:28 AM
To: Discussion of precise time and frequency measurement
Cc: hmur...@megapathdsl.net
Subject: Re:
Gary wrote:
I try to minimize dangerous voltages. Anyway, the filtering reduces the
slew, so you can't have it both ways.
Starting with 120v gives you 10x the slew rate that starting with 12v
does, whatever filtering you use.
If by post processing you are averaging, then you certainly hav
On Thu, 18 Dec 2014 04:26:22 -0500
Charles Steinmetz wrote:
> Gary wrote:
>
> >Why not use a lower voltage transformer, preferably not at a lethal
> >voltage. You only need a couple of volts to drive the rest of the
> >circuit.
>
> As you can see from the schematic, the voltage is diode-clampe
Historically the problem with "grass" causing double counts has been dealt
with by having a one shot that disables retriggering for almost a whole
cycle. This is pretty much every line powered digital clock from the 70's.
If you set the one shot to be for 9.5 cycles then you just invented a whole
Hal wrote:
What sort of interference do you see?
There is a general "grass" on the entire waveform. At our location,
the tops of the sine wave are clipped off (as the power is
delivered). See attached image (the orange trace is the AC we
receive from the grid; cyan is the distortion resid
sidegnss.com/node/4281
>
> Mike
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray
> Sent: Wednesday, December 17, 2014 3:28 AM
> To: Discussion of precise time and frequency measurement
> Cc: hmur...@megapathd
me-nuts-boun...@febo.com] On Behalf Of Hal Murray
Sent: Wednesday, December 17, 2014 3:28 AM
To: Discussion of precise time and frequency measurement
Cc: hmur...@megapathdsl.net
Subject: Re: [time-nuts] Simple AC mains zero-cross detector
csteinm...@yandex.com said:
> That one is not ideal for th
csteinm...@yandex.com said:
> The circuit presented allows one data collection to do both functions well.
> It has enough filtering to prevent local interference from corrupting the
> data, it can locate 60Hz zero crossings to within 1uS (i.e., frequency
> resolution significantly better than
Gary wrote:
Why not use a lower voltage transformer, preferably not at a lethal
voltage. You only need a couple of volts to drive the rest of the
circuit.
As you can see from the schematic, the voltage is diode-clamped
almost immediately to ~ +/- 1.5v. The reason for using a 120v
winding i
I actually needed to do real ZCD for thyristor switching off incredibly
noisy bad AC suppplies used down mines in third world countries. I used a
digital PLL to lock to the AC line volts waveform with a simple detector
with a threshold of 50V set by a zener driving an opto. I think the loop
time co
Gary wrote:
Why not use a lower voltage transformer, preferably not at a lethal
voltage. You only need a couple of volts to drive the rest of the
circuit.
As you can see from the schematic, the voltage is diode-clamped
almost immediately to ~ +/- 1.5v. The reason for using a 120v
winding i
Gary wrote:
Zero crossing and frequency measurement are not the same thing.
Generally you zero cross detect to switch a load with the minimum
glitch. For frequency measurement, I'd filter the signal before
counting it.
Grid-nuts are interested in *both* the instantaneous frequency of the
gri
On Thu, 18 Dec 2014 01:26:06 -0500
Charles Steinmetz wrote:
> There has been some lively debate about how much filtering (if any)
> is acceptable here. On the one hand, the AC line is a very noisy
> source at frequencies above the fundamental, while the fundamental
> frequency is determined
Zero crossing and frequency measurement are not the same thing.
Generally you zero cross detect to switch a load with the minimum
glitch. For frequency measurement, I'd filter the signal before
counting it. But of course a filter will shift the waveform, making it
not useful for a zero crossing det
On 12/17/14, 6:46 AM, Chuck Forsberg WA7KGX wrote:
Seems to me CFLs and other loads switching on and off would affect the
60 Hz waveform
enough to make microsecond measurements meaningless.
folks measure the frequency to tenths of a Hz (albeit not a single cycle)..
0.1 Hz out of 60 Hz is 27 m
Seems to me CFLs and other loads switching on and off would affect the
60 Hz waveform
enough to make microsecond measurements meaningless.
On 12/17/2014 01:03 AM, Charles Steinmetz wrote:
Hal wrote:
What are you going to do with data from the line accurate to 1
microsecond?
Me? Nothing. I
Hi
> On Dec 17, 2014, at 3:27 AM, Hal Murray wrote:
>
>
> csteinm...@yandex.com said:
>> That one is not ideal for this task, because (i) its output pulse is
>> symmetrical about the mains zero cross, and (ii) the hysteresis zone is not
>> well characterized and will drift with temperature and
Hi
> On Dec 16, 2014, at 11:03 PM, Charles Steinmetz wrote:
>
> Bob wrote:
>
>> The Collins paper on hard limiters does indeed apply here. You *could* make
>> a 60 Hz chain that got down into << 1 us sort of resolution.
>
> I don't know how "much less than" 1uS you mean by "<<", but I was see
Hal wrote:
What are you going to do with data from the line accurate to 1 microsecond?
Me? Nothing. I don't find the meanderings of the mains frequency
all that interesting, aside from observing them from time to time via
the sweep second hand of a synchronous wall clock. But lots of othe
csteinm...@yandex.com said:
> That one is not ideal for this task, because (i) its output pulse is
> symmetrical about the mains zero cross, and (ii) the hysteresis zone is not
> well characterized and will drift with temperature and input voltage. So,
> there is no edge that is well characteri
Dave wrote:
I'm not trying to downplay the circuit in the link above, but I want
to offer another possible solution to Zero-Crossing needs.
Here's an Idea For Design from EDN magazine that I've used a couple
times in non-time-nut circuits, and I must say that it works
beautifully. I have no
Bob wrote:
The Collins paper on hard limiters does indeed apply here. You
*could* make a 60 Hz chain that got down into << 1 us sort of resolution.
I don't know how "much less than" 1uS you mean by "<<", but I was
seeing less than 1uS jitter with the circuit described.
Best regards,
Charle
Hi
Indeed looking at the AC line is a Time Nut sort of thing to do. It was one of
the first things I did with an old Beckman counter back in the 1960’s. Yes I
realize that the AC line is a very noisy signal and that this may not be needed:
The same limiter / noise shaper stuff that works for a
Charles Steinmetz wrote:
Every so often, the subject of logging the zero-crossings of the AC
mains comes up. There are any number of ways to couple the AC mains
to logic circuitry (coupling with very high value resistors,
capacitor coupling, and optical isolation have been mentioned). A
simple
Every so often, the subject of logging the zero-crossings of the AC
mains comes up. There are any number of ways to couple the AC mains
to logic circuitry (coupling with very high value resistors,
capacitor coupling, and optical isolation have been mentioned). A
simple AC mains ZCD that is tr
39 matches
Mail list logo
