Re: [time-nuts] Simple AC mains zero-cross detector
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 is to simply connect the 60Hz signal to the DTR line of a serial port on the computer. The computer then make a time take file. Accuracy of this is roughly a couple uSec. On Sun, Dec 21, 2014 at 10:04 PM, nuts n...@lazygranch.com wrote: On Sun, 21 Dec 2014 17:37:07 -0500 Charles Steinmetz csteinm...@yandex.com 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-crossing velocity could be the same. An IC tripping in a 10 mV band should provide the same effective ZC velocity at 12 V input as a transistor working around 100 mV with 120 V input. Or am I missing something? When the switching band gets that small, device noise, input offset voltage drift, and other errors have a proportionally greater effect. I actually built a similar circuit with a 12v transformer and an LT1720 comparator, and it had worse jitter than the two-transistor circuit with a 120v feed. In this case, there is no substitute for starting with a higher-slew-rate signal. (Yes, the LT1720 did marginally better than the two-transistor circuit when both were fed from 120v -- but the fussiness of working with a fast comparator and the small gain over the two-transistor circuit made the latter the better choice, particularly in a design being put out there for others to build.) Best regards, Charles Looking at the data sheet of the LT1720, 1mv would have about 8ns delay. Call it 10ns. A Vp of 29 volts should be sufficient to put the delay around 90ns, making 100ns error or target percent of the 1uS target. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
On Sun, 21 Dec 2014 17:37:07 -0500 Charles Steinmetz csteinm...@yandex.com 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-crossing velocity could be the same. An IC tripping in a 10 mV band should provide the same effective ZC velocity at 12 V input as a transistor working around 100 mV with 120 V input. Or am I missing something? When the switching band gets that small, device noise, input offset voltage drift, and other errors have a proportionally greater effect. I actually built a similar circuit with a 12v transformer and an LT1720 comparator, and it had worse jitter than the two-transistor circuit with a 120v feed. In this case, there is no substitute for starting with a higher-slew-rate signal. (Yes, the LT1720 did marginally better than the two-transistor circuit when both were fed from 120v -- but the fussiness of working with a fast comparator and the small gain over the two-transistor circuit made the latter the better choice, particularly in a design being put out there for others to build.) Best regards, Charles Looking at the data sheet of the LT1720, 1mv would have about 8ns delay. Call it 10ns. A Vp of 29 volts should be sufficient to put the delay around 90ns, making 100ns error or target percent of the 1uS target. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
On Sat, 20 Dec 2014 18:31:29 -0500 Mike Garvey r3m...@verizon.net 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 One overkill AFSK demod is to sample the signal and compute the arcsin, essentially producing a straight line of phase versus time. We had made a AFSK demod using linear regression on this line to determine frequency. This isn't overkill when you have a DSP chip there anyway. Now I don't see a reason why similar analysis couldn't be done with power line monitoring. Over some moving window of time, you could even produce the difference signal between the sine wave due to the regression fitting from the raw signal and thus display the noise on the line. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 occur even with no load. The resistive loss will go up more with load. But, I don't think this matters in this application anyway. Ed ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 not, myself, a grid-nut), and the reason the simple ZCD circuit uses this approach. But grid-nuts are also interested in perturbations of the grid voltage caused by grid sections going offline and coming back, lightning strikes, etc., etc. (After all, simply monitoring the ebb and flow of the line frequency is about as interesting as watching the tide come in and go out, so they naturally want some occasional excitement.) These anomalies can be detected by their effect on the zero crossings of the mains voltage, so one data collection serves both purposes at the time-nuts level. While the ZCD approach is ideal for monitoring the grid phase/frequency, and as a bonus provides timing information about grid anomalies, it does not capture all of the information about anomalies. If you are a utility concerned about grid security or making sure that new energy sources play nicely with the grid, you probably want more information about anomalies than time-stamped zero crossings provide. Magnus described a system used by utilities to track grid anomalies in greater detail. My reply agreed that zero cross detection is not the tool of choice for utilities with such concerns, and noted the different needs of grid-nuts and utilities. Grid-nuts are well established, and the vast majority of them use time-stamped zero crossings as their data sets. I was concerned that many grid-nuts seem to use non-isolated feeds from the mains that, while safe enough under normal conditions, are not preferred practice. I also thought that the timing relationship between the ZCD and the actual zero cross could be improved and stabilized with a new ZCD. So, I designed the simple ZCD circuit to provide an isolated source of very predictably timed pulses with fast edges. I tested it and it proved to be reliable and to have very stable timing with respect to the line zero crossings, so I published it and announced it on-list with the first message in this thread. Since then, the thread has taken on a life of its own and ranged very far from the initial, simple proposition of improved zero cross detection. There has been a flurry of comments mostly aimed not at whether the simple ZCD is a good AC mains zero cross detector, but more toward whether zero crossings are what grid-nuts should be interested in in the first place. Since I am not, myself, a grid-nut, I cannot really speak to what grid-nuts should be interested in. I do think that time-stamped zero crossings have many significant advantages when one is interested in comparing notes with others, and it is comparatively easy data to collect with good accuracy -- so, IMO, the choice of grid-nuts to settle on time-stamped zero crossings was eminently rational. The simple ZCD has proven to be an excellent front end for such a data collection, and is a project within the skills of anyone who knows which end of a soldering iron to grip. I am happy to answer any questions that potential builders may have. Personally, I think the thread has more than run its course and should be laid to rest. But if it is to continue, please accept as a given that grid-nuts decided long ago that time-stamped zero crossings are the appropriate data to collect, and focus on the narrow topic of the simple ZCD as a means for accurately detecting zero crossings of the AC mains. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 isolation between primary and secondary, which could be a safety hazard. Since small transformers with a 120V primary and a true 120V secondary are hard to find, a better way would be to use two regular step-down transformers back to back, like two door bell transformers: 120-24-120. You would then get double isolation. Didier KO4BB On Sun, Dec 21, 2014 at 2:52 AM, Charles Steinmetz csteinm...@yandex.com wrote: 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 not, myself, a grid-nut), and the reason the simple ZCD circuit uses this approach. But grid-nuts are also interested in perturbations of the grid voltage caused by grid sections going offline and coming back, lightning strikes, etc., etc. (After all, simply monitoring the ebb and flow of the line frequency is about as interesting as watching the tide come in and go out, so they naturally want some occasional excitement.) These anomalies can be detected by their effect on the zero crossings of the mains voltage, so one data collection serves both purposes at the time-nuts level. While the ZCD approach is ideal for monitoring the grid phase/frequency, and as a bonus provides timing information about grid anomalies, it does not capture all of the information about anomalies. If you are a utility concerned about grid security or making sure that new energy sources play nicely with the grid, you probably want more information about anomalies than time-stamped zero crossings provide. Magnus described a system used by utilities to track grid anomalies in greater detail. My reply agreed that zero cross detection is not the tool of choice for utilities with such concerns, and noted the different needs of grid-nuts and utilities. Grid-nuts are well established, and the vast majority of them use time-stamped zero crossings as their data sets. I was concerned that many grid-nuts seem to use non-isolated feeds from the mains that, while safe enough under normal conditions, are not preferred practice. I also thought that the timing relationship between the ZCD and the actual zero cross could be improved and stabilized with a new ZCD. So, I designed the simple ZCD circuit to provide an isolated source of very predictably timed pulses with fast edges. I tested it and it proved to be reliable and to have very stable timing with respect to the line zero crossings, so I published it and announced it on-list with the first message in this thread. Since then, the thread has taken on a life of its own and ranged very far from the initial, simple proposition of improved zero cross detection. There has been a flurry of comments mostly aimed not at whether the simple ZCD is a good AC mains zero cross detector, but more toward whether zero crossings are what grid-nuts should be interested in in the first place. Since I am not, myself, a grid-nut, I cannot really speak to what grid-nuts should be interested in. I do think that time-stamped zero crossings have many significant advantages when one is interested in comparing notes with others, and it is comparatively easy data to collect with good accuracy -- so, IMO, the choice of grid-nuts to settle on time-stamped zero crossings was eminently rational. The simple ZCD has proven to be an excellent front end for such a data collection, and is a project within the skills of anyone who knows which end of a soldering iron to grip. I am happy to answer any questions that potential builders may have. Personally, I think the thread has more than run its course and should be laid to rest. But if it is to continue, please accept as a given that grid-nuts decided long ago that time-stamped zero crossings are the appropriate data to collect, and focus on the narrow topic of the simple ZCD as a means for accurately detecting zero crossings of the AC mains. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 have they had anything done to improve the fidelity of the signal they pass. Typically, they are running very near the edge where the core is entering saturation, not because it is a good thing, but rather because it minimizes the amount of copper and iron, and the physical size necessary, for a given amount of power output The trade off being efficiency... a little more heat is generated, and that is the customer's problem to deal with, not the manufacturer's... but I digress. In the 99 and 44/100 th's percent of the usage of a transformer coupled ZCD, the positive and negative zero crossings are going to come chugging along predictably about every 8.3 milliseconds. And, the degree which their arrival is unpredictably 8.... milliseconds, is what I believe to be the the realm of the grid-nut. One facet of that unpredictability is what I am interested in, for the purposes of this post: Suppose, that one of the grid-nut persuasion is interested in the timing of the occasional crash transient where somewhere during the course of a cycle, an unintentional zero crossing occurs due to a transient that drags the grid voltage through ground. With an opto isolator protected ZCD, the transient will be propagated to the logic side by way of the usual speed of light, and will remain true to the fixed delay introduced by the optoisolator ZCD... The optoisolated ZCD has no ability to affect where the crossings occur, or for the most part, how often the crossings occur; it will faithfully register and send the glitch along to the logic side for measurement. A transformer isolated ZCD, is different in this regard, however. Because of the nature of transformers, a transformer isolated ZCD will propagate every of the various frequencies it passes, with a different delay. What this means, is that as long as the zero crossings keep chugging along at a nominally 60Hz rate, you will have your touted sub-microsecond timing accuracy; but, introduce one crash transient that causes a significantly early zero crossing, and you will be introducing frequency components other than 60Hz, and will cause the crash transient's time-of-occurrence to be misrepresented, and will also cause the subsequent zero crossing's time-of-occurrence to be misrepresented... all due to the transformer's inability to induce all frequencies with the same speed. This same uncertainty will occur even if the so called crash transient does not pull the sine wave all the way to zero, but only wounds it a little. Thoughts? -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 same effective ZC velocity at 12 V input as a transistor working around 100 mV with 120 V input. Or am I missing something? Ed ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 the isolation between primary and secondary, which could be a safety hazard. Since small transformers with a 120V primary and a true 120V secondary are hard to find, a better way would be to use two regular step-down transformers back to back, like two door bell transformers: 120-24-120. You would then get double isolation. The transformer I used is a dual C core pseudo-toroid -- it has one primary and one secondary winding on one bobbin and the other primary and secondary winding on the other bobbin (on the opposite side of the core). The primary-to-primary isolation of any transformer wound this way should actually be better than its primary-to-secondary isolation. Of course, not all small power transformers are built this way. However, the primary-to-primary isolation of any small commercial power transformer should be sufficient not to cause any safety problems in the ZCD application. Hipot ratings are regulated by standards and are generally greater than 1500v from any winding to any other winding, and even if there were an effective interwinding capacitance of 200pF between primary windings, the 60Hz current in the ZCD ground would be no more than single-digit uA at a maximum. (By comparison, ground-fault interruptors trip at 4-6mA -- 1000 times greater than this.) The actual effective primary-to-primary capacitance is likely to be very much less than 200pF, and the capacitive leakage current from the 120v to 120v isolation windings should be comparable to the capacitive leakage from the Vcc supply. All that said, there is certainly nothing wrong with using two transformers back to back, as you suggest, to improve isolation. It is also how anyone in a 200 or 240v country would generate isolated 120v: 240:12 == 24:240. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 provide the same effective ZC velocity at 12 V input as a transistor working around 100 mV with 120 V input. Or am I missing something? When the switching band gets that small, device noise, input offset voltage drift, and other errors have a proportionally greater effect. I actually built a similar circuit with a 12v transformer and an LT1720 comparator, and it had worse jitter than the two-transistor circuit with a 120v feed. In this case, there is no substitute for starting with a higher-slew-rate signal. (Yes, the LT1720 did marginally better than the two-transistor circuit when both were fed from 120v -- but the fussiness of working with a fast comparator and the small gain over the two-transistor circuit made the latter the better choice, particularly in a design being put out there for others to build.) Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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. I frequently recommend small 120:12v or 120:6.3v power transformers as 600 ohm line to voice coil transformers for audio applications. I have tested scores of them, and have yet to find one that is not flat from at least 20Hz to 15kHz -- often significantly better -- if operated at no more than 1/2 its rated 60Hz power. The distortion is typically 1% at that power level. [I have not measured transformers from wall warts, but I expect that many if not most of them conform to the same general specs.] Typically, they are running very near the edge where the core is entering saturation, That depends on the current you are drawing. The ZCD circuit doesn't draw anywhere close to the transformer's rated current, so core saturation is no worry at all. Because of the nature of transformers, a transformer isolated ZCD will propagate every of the various frequencies it passes, with a different delay. The transformer's group delay is not an issue at the 1uS level. However, the input filter I specified has non-constant group delay, which varies about 40uS from 10Hz to 600Hz (the range of frequencies where I observed significant components of grid transients). So, there is a tradeoff. If accurate timing of transients is more important than some spurious noise responses, the ZCD should be built without the filter capacitors (C1 and C5 on the schematic), as noted in the description. In that case, the group delay is within 1uS for all frequencies above ~10Hz. Note that this also applies to any other detector, including those using optoisolators -- any input filtering will create non-constant group delay. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Gary n...@lazygranch.com 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 have lost frequency variation data. Averaging is a filter. You will not lose grid frequency variation data unless you average the 60 per second samples for *extremely* long periods of time, because the grid frequency is generated by rotating machinery weighing many tons that can only change frequency very, very slowly. As I noted before, the simple system I described resolves frequency to better than 0.01 Hz in one cycle, so very little averaging is needed to achieve better resolution than anyone really cares about. As long as the averaging function is more agile than the actual grid (and it will be under all practical conditions), all actual grid frequency variations will be preserved. You proposed a method using steep hardware filtering, which presumably you do not think loses frequency variation data. The system I described can easily duplicate whatever filter you propose, in post-processing. So either your proposed system cannot track grid frequency variations, or my [built and tested] system can. You can't have it both ways. If the event is due to noise, you resolved essentially garbage to a microsecond. No, you resolved a grid phenomenon in which grid-nuts are interested to within a microsecond. If you average, you have done filtering. Yes, but for the reasons given above and in the other messages in this thread it is benign filtering that does not obscure any of the grid voltage features grid-nuts are trying to record. Furthermore, it is done in post-processing so you can re-do it at will to resolve whatever you want to resolve. You proposed a scheme with steep hardware filtering, which does not have this flexibility. This is getting tedious. If you are interested in grid logging, please build one of the simple systems I described and one of whatever system you think will work better, and present data to support your conjectures. Until then, you really aren't contributing anything useful to the discussion. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Yes, PMUs makes it a bit different. Here is a random paper someone wrote: https://rubidium.dyndns.org/~magnus/papers/KTH_paper1.pdf PMUs samples at some high frequency, mixes down the network frequency to base-band, filters away the mirror frequency before sub-sampling it into the configured sample-rate. The process is being controlled by the IEEE C37.118.1 standard, while the communication is described in IEEE C37.118.2 but an IEC 61850 extension provides for another way of conveying that data. PMUs have proven themselves to outperform many of the normal frequency and ROCOF estimators, which became evident in the 2003 NE black-out scenario, as the SCADA data kept getting them on the wrong tracks, so after 8 months they just scrapped the frequency readings from the traditional equipment and just looked at the PMU data, they could sort the events out properly in time. Turns out that the details of how a particular vendor implements the frequency estimation and filtering can be devastating in getting comparable frequency measures, and thus loosing the observation precision needed to follow the aftermath properly. The C37.118.1 has put a stringency on how filtering is to be done, as well as how frequency and ROCOF (Rate Of Change Of Frequency) is to be calculated. NIST has a small department focusing on the calibration of PMUs, and is working actively with the vendors to get them improved. Good folks and I have helped them a little with some ideas, amongst others to do through-zero calibrators. For other events, Digital Fault Recorders (DFR) is being used. They are essentially memory oscilloscopes which have a more advanced trigger adapted to go off on all interesting events. Today DFRs is a legal requirement in some countries. So, I do not completely agree that a through-zero measurement with a TIC has all the information, and for the information you do get, you would like to be as careful as the PMU folks about the group-delay of filters, time-compensation of processing and filters etc. to maintain good precision. There is reason to look at it and learn. Cheers, Magnus On 12/18/2014 11:59 PM, Mike Garvey wrote: There is an interesting article in the Nov/Dec issue of Inside GNSS describing the robust measurement of ...voltage and current phasors at widely dispersed locations in a power grid. A Phase Measurement Unit measures and time stamps the voltage and current phasors ...thousands of times per second... to an accuracy of 1 us using GPS. The authors discuss several strategies for dealing with jamming and spoofing of the civil GPS signals. It's a good 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: [time-nuts] Simple AC mains zero-cross detector 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 characterized in relation to the AC mains zero cross. What are you going to do with data from the line accurate to 1 microsecond? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Charles, On 12/20/2014 09:24 AM, Charles Steinmetz wrote: Gary n...@lazygranch.com 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 have lost frequency variation data. Averaging is a filter. You will not lose grid frequency variation data unless you average the 60 per second samples for *extremely* long periods of time, because the grid frequency is generated by rotating machinery weighing many tons that can only change frequency very, very slowly. As I noted before, the simple system I described resolves frequency to better than 0.01 Hz in one cycle, so very little averaging is needed to achieve better resolution than anyone really cares about. As long as the averaging function is more agile than the actual grid (and it will be under all practical conditions), all actual grid frequency variations will be preserved. As you look careful on the phase variations, you will find that you have forced oscillations being pushed onto the network, some extending into several hertz and in one case a wind-farm had a 13 Hz forced oscillation being pushed out on the power grid. Also, there is inter-area oscillations creating resonant modes on the power-grid. These can either be fed from generators injecting energy into the mode or cause variations as breakers, transformer tappings or change of load occurs. Things have been discovered when looking deeper into the phase variations with faster speeds. Besides doing wide-area monitoring, starting to use these observations to steer stabilizers have been discussed and tested. The development goes quickly in the power-grid world at the moment. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 zero cross) could hide and show nothing more than a slight displacement of one or two zero crosses. Grid-nuts can ignore such short glitches. Utilities can't, particularly in today's cybersecurity environment. Horses for courses. From my observations of the AC mains while I was testing the simple ZCD, I would expect such hidden glitches [that are real grid-related phenomena, not just someone starting a motor downstairs] to be very rare. The grid phenomena I saw typically last more than one grid cycle and thus affect more than one zero cross, and/or are large in magnitude and cause serious displacement of at least one zero crossing, or several extra zero crossings. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 -Original Message- From: time-nuts [mailto:time-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 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 zero cross) could hide and show nothing more than a slight displacement of one or two zero crosses. Grid-nuts can ignore such short glitches. Utilities can't, particularly in today's cybersecurity environment. Horses for courses. From my observations of the AC mains while I was testing the simple ZCD, I would expect such hidden glitches [that are real grid-related phenomena, not just someone starting a motor downstairs] to be very rare. The grid phenomena I saw typically last more than one grid cycle and thus affect more than one zero cross, and/or are large in magnitude and cause serious displacement of at least one zero crossing, or several extra zero crossings. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Simple AC mains zero-cross detector
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 class of frequency dividers as illustrated in a couple chapters of the MIT Rad Lab books. Phantasmotron is what I recall but google produces nothing useful from that. You can further enhance stability in grass by low-pass filtering and detecting slope as a precondition. Then the circuit looks a lot like an oscilloscope trigger and timebase. indeed certain brands of scope had truly ecexcellent triggers while others that had similar specs were crap. If you super duper want to lock to a noisy line you just dust off the lock in amplifier. Seems like overkill because these are traditionally used when the signal is much smaller than the noise. Tim N3QE On Thursday, December 18, 2014, Charles Steinmetz csteinm...@yandex.com javascript:_e(%7B%7D,'cvml','csteinm...@yandex.com'); wrote: 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 residual from a distortion analyzer -- there are rich harmonics out to the 20th or so within -50dB of the fundamental). The image is not properly scaled to show the high-frequency grass. What does an interesting transient event look like? It all depends. They are not all that fast (unless your house feed gets struck by lightning, in which case what does it look like in the data collection is the least of your worries), and usually comparable in amplitude to the power signal +/- 10dB (again, unless there is a very close lightning strike), so they generate extra zero crossings spaced anywhere from low mS to tens of mS. If you are going to post-process the data anyway, why not collect raw data and let the post-processing take care of the local interference? That lets you defer decisions about the appropriate filtering. There is enough high-frequency grass to reduce the precision of your zero crossing determinations. Since there is no useful information on grid behavior at these frequencies, it is better to remove it to improve your zero-cross precision. You can do a lot with post-processing, but you can't fix EVERYTHING in the mix. You have to start with the best data collection you can get, which in this case means filtering out the low-amplitude stuff above 1kHz or so. Is there any database of events that I can check when I see something interesting? Or turn things around and pick an event and see what it looks like when it gets here? Not that I'm aware of. (But as I noted previously, I'm not personally a grid-nut). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
On Thu, 18 Dec 2014 04:26:22 -0500 Charles Steinmetz csteinm...@yandex.com wrote: Gary n...@lazygranch.com 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 is to take advantage of the free slope enhancement provided by the higher voltage. The 120v winding provides a signal with a zero-cross slew rate of ~65mV/uS. A 12v winding would slew only ~6.5mV/uS. The faster the slew rate, the more accurately one can locate the zero crossings. I try to minimize dangerous voltages. Anyway, the filtering reduces the slew, so you can't have it both ways. If you are going to look at glitches, that should be done by sampling the AC (transformer coupled obviously). Basically the circuit to detect period is dedicated to that function. Since the frequency won't vary significantly, a high order filter wouldn't be an issue, as long as you don't care about delay. You are suggesting two separate data collections, one geared toward grid frequency and one geared toward glitch detection. That's fine, and might be preferable if it provided better results than using just one data collection. But using a higher-order hardware filter does not provide better frequency determination than post-processing the ZCD data. If by post processing you are averaging, then you certainly have lost frequency variation data. Averaging is a filter. 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 0.01 Hz, single-shot, which can be filtered/averaged to get whatever resolution you want in post-processing), and it can locate transient events to within 1uS. Win-win. If the event is due to noise, you resolved essentially garbage to a microsecond. If you average, you have done filtering. I don't see this as a win-win. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
On Thu, 18 Dec 2014 01:26:06 -0500 Charles Steinmetz csteinm...@yandex.com 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 mainly by massive rotating machinery that cannot change frequency very quickly. On the other hand, if you pass the signal through a narrow filter you could miss the glitches that interest the folks who collect such data (grid switching transients, lightning strikes, etc.), or they could be delayed and smeared out in time so determining when they occurred would be problematic. The filtering in the circuit I posted (two-pole RC lowpass with a -3dB frequency of ~475 Hz) is a good compromise. It filters out the worst of the locally-generated hash without masking grid events. For those who want their data raw, the filter can be omitted as noted in the description sheet that accompanies the schematic. (You did download and read the material before posting about it, right?) Of course I looked at the schematic. It is a very basic cascade of single pole RC filters with components separated by a factor of 10 to prevent component interaction. Not much of a filter and the corner is probably a bit soft considering the load impedance is not infinite, but rather a switch. 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. If you are going to look at glitches, that should be done by sampling the AC (transformer coupled obviously). Basically the circuit to detect period is dedicated to that function. Since the frequency won't vary significantly, a high order filter wouldn't be an issue, as long as you don't care about delay. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Gary n...@lazygranch.com 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 grid and also the transients indicative of grid events (grid switching transients, lightning strikes, etc.). So, a data collection system for grid-nuts must capture data sufficient to determine both the instantaneous grid frequency and the time-of-occurrence of grid events. If you time stamp the zero crossings, you have all of the information you need to compute frequency with any desired windowing, filtering, or averaging function you desire (and much more). So, yes, they are the same thing when the thing is frequency measurement, but ZCD gives you the freedom to set the filtering parameters in post-processing rather than at hardware design time. Of course, in addition to whatever windowing/filtering/averaging algorithm you may apply in post-processing, you can also filter the signal at the data collection stage. This can improve the accuracy of frequency determinations where little post-processing averaging is done (what a time-nut would think of as low-tau measurements). 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 mainly by massive rotating machinery that cannot change frequency very quickly. On the other hand, if you pass the signal through a narrow filter you could miss the glitches that interest the folks who collect such data (grid switching transients, lightning strikes, etc.), or they could be delayed and smeared out in time so determining when they occurred would be problematic. The filtering in the circuit I posted (two-pole RC lowpass with a -3dB frequency of ~475 Hz) is a good compromise. It filters out the worst of the locally-generated hash without masking grid events. For those who want their data raw, the filter can be omitted as noted in the description sheet that accompanies the schematic. (You did download and read the material before posting about it, right?) Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Gary n...@lazygranch.com 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 is to take advantage of the free slope enhancement provided by the higher voltage. The 120v winding provides a signal with a zero-cross slew rate of ~65mV/uS. A 12v winding would slew only ~6.5mV/uS. The faster the slew rate, the more accurately one can locate the zero crossings. If you are going to look at glitches, that should be done by sampling the AC (transformer coupled obviously). Basically the circuit to detect period is dedicated to that function. Since the frequency won't vary significantly, a high order filter wouldn't be an issue, as long as you don't care about delay. You are suggesting two separate data collections, one geared toward grid frequency and one geared toward glitch detection. That's fine, and might be preferable if it provided better results than using just one data collection. But using a higher-order hardware filter does not provide better frequency determination than post-processing the ZCD data. 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 0.01 Hz, single-shot, which can be filtered/averaged to get whatever resolution you want in post-processing), and it can locate transient events to within 1uS. Win-win. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 constant was set very slow, several seconds as the AC came from a gererator so very slow to change as you have the inertia of the massive armature in the generator. Logging this over several days on the mains network showed it slowing slightly during the day and then speeding up at night to give the right number of cycles per day. It was insensitive to voltage. We did find that isolating the zener opto via a transformer gave a temperature dependant phase shift, exactly what you don't want for switching thyristors. Tom Harris celephi...@gmail.com On 19 December 2014 at 08:16, Charles Steinmetz csteinm...@yandex.com wrote: Gary n...@lazygranch.com 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 is to take advantage of the free slope enhancement provided by the higher voltage. The 120v winding provides a signal with a zero-cross slew rate of ~65mV/uS. A 12v winding would slew only ~6.5mV/uS. The faster the slew rate, the more accurately one can locate the zero crossings. If you are going to look at glitches, that should be done by sampling the AC (transformer coupled obviously). Basically the circuit to detect period is dedicated to that function. Since the frequency won't vary significantly, a high order filter wouldn't be an issue, as long as you don't care about delay. You are suggesting two separate data collections, one geared toward grid frequency and one geared toward glitch detection. That's fine, and might be preferable if it provided better results than using just one data collection. But using a higher-order hardware filter does not provide better frequency determination than post-processing the ZCD data. 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 0.01 Hz, single-shot, which can be filtered/averaged to get whatever resolution you want in post-processing), and it can locate transient events to within 1uS. Win-win. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Gary n...@lazygranch.com 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 is to take advantage of the free slope enhancement provided by the higher voltage. The 120v winding provides a signal with a zero-cross slew rate of ~65mV/uS. A 12v winding would slew only ~6.5mV/uS. The faster the slew rate, the more accurately one can locate the zero crossings. If you are going to look at glitches, that should be done by sampling the AC (transformer coupled obviously). Basically the circuit to detect period is dedicated to that function. Since the frequency won't vary significantly, a high order filter wouldn't be an issue, as long as you don't care about delay. You are suggesting two separate data collections, one geared toward grid frequency and one geared toward glitch detection. That's fine, and might be preferable if it provided better results than using just one data collection. But using a higher-order hardware filter does not provide better frequency determination than post-processing the ZCD data. 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 0.01 Hz, single-shot, which can be filtered/averaged to get whatever resolution you want in post-processing), and it can locate transient events to within 1uS. Win-win. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 0.01 Hz, single-shot, which can be filtered/averaged to get whatever resolution you want in post-processing), and it can locate transient events to within 1uS. Win-win. What sort of interference do you see? What does an interesting transient event look like? If you are going to post-process the data anyway, why not collect raw data and let the post-processing take care of the local interference? That lets you defer decisions about the appropriate filtering. Is there any database of events that I can check when I see something interesting? Or turn things around and pick an event and see what it looks like when it gets here? I've been collecting frequency data for my local power line. I grab the PPS style time stamps and counts from a modem control pin every 10 seconds. No filtering, just a transformer. I occasionally get an extra count. It's pretty obvious when you look at the graphs. They happen ballpark of once a month. A while ago, I was trying to capture the audio too, so I could look at the area around the extra counts. I never got anything clean. I think that setup had grounding problems. Maybe it's time to try again. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
There is an interesting article in the Nov/Dec issue of Inside GNSS describing the robust measurement of ...voltage and current phasors at widely dispersed locations in a power grid. A Phase Measurement Unit measures and time stamps the voltage and current phasors ...thousands of times per second... to an accuracy of 1 us using GPS. The authors discuss several strategies for dealing with jamming and spoofing of the civil GPS signals. It's a good 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: [time-nuts] Simple AC mains zero-cross detector 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 characterized in relation to the AC mains zero cross. What are you going to do with data from the line accurate to 1 microsecond? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Hi Using GPS timing for power network analysis and control dates back into the 1980’s. The guys at Quebec Hydro set up the first system I’m aware of. They had tried it with Loran-C before, but the noise in the vicinity of a major power station made that impossible. GPS being microwave helped them a lot with that part of it. They did a paper at FCS(?) on the results. Back then being able to actually get very accurate phase data over a 100’s of mile range was a pretty novel thing. Using GPS timing for this actually pre-dates the whole CDMA / GPSDO thing. Bob On Dec 18, 2014, at 5:59 PM, Mike Garvey r3m...@verizon.net wrote: There is an interesting article in the Nov/Dec issue of Inside GNSS describing the robust measurement of ...voltage and current phasors at widely dispersed locations in a power grid. A Phase Measurement Unit measures and time stamps the voltage and current phasors ...thousands of times per second... to an accuracy of 1 us using GPS. The authors discuss several strategies for dealing with jamming and spoofing of the civil GPS signals. It's a good 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: [time-nuts] Simple AC mains zero-cross detector 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 characterized in relation to the AC mains zero cross. What are you going to do with data from the line accurate to 1 microsecond? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 residual from a distortion analyzer -- there are rich harmonics out to the 20th or so within -50dB of the fundamental). The image is not properly scaled to show the high-frequency grass. What does an interesting transient event look like? It all depends. They are not all that fast (unless your house feed gets struck by lightning, in which case what does it look like in the data collection is the least of your worries), and usually comparable in amplitude to the power signal +/- 10dB (again, unless there is a very close lightning strike), so they generate extra zero crossings spaced anywhere from low mS to tens of mS. If you are going to post-process the data anyway, why not collect raw data and let the post-processing take care of the local interference? That lets you defer decisions about the appropriate filtering. There is enough high-frequency grass to reduce the precision of your zero crossing determinations. Since there is no useful information on grid behavior at these frequencies, it is better to remove it to improve your zero-cross precision. You can do a lot with post-processing, but you can't fix EVERYTHING in the mix. You have to start with the best data collection you can get, which in this case means filtering out the low-amplitude stuff above 1kHz or so. Is there any database of events that I can check when I see something interesting? Or turn things around and pick an event and see what it looks like when it gets here? Not that I'm aware of. (But as I noted previously, I'm not personally a grid-nut). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 characterized in relation to the AC mains zero cross. What are you going to do with data from the line accurate to 1 microsecond? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 other folks do (including our fearless leader, tvb), and they like being able to correlate grid events to single-digit uS (lightning strikes, sections of the grid going out, etc.). That said, I didn't slave away trying to get the ZCD jitter below 1uS -- I anticipated that it would be, just because there's nothing in the design to prevent it, so I wasn't surprised when it worked out that way. Best regards, Charles = Everything works if you let it. Corpus C. Redfish = ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Hi On Dec 16, 2014, at 11:03 PM, Charles Steinmetz csteinm...@yandex.com 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 seeing less than 1uS jitter with the circuit described. … as in sub ns if you wish to put in enough stages in the chain. The number of stages is a limit on how good you get. 12 or more stages seems a bit over the limit for this sort of thing. Thus the indeterminate units. Bob Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
Hi On Dec 17, 2014, at 3:27 AM, Hal Murray hmur...@megapathdsl.net 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 input voltage. So, there is no edge that is well characterized in relation to the AC mains zero cross. What are you going to do with data from the line accurate to 1 microsecond? or a nanosecond … Obviously it would depend on just what your system needed to do and the signal to noise on the 60 Hz input. Bob -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 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 other folks do (including our fearless leader, tvb), and they like being able to correlate grid events to single-digit uS (lightning strikes, sections of the grid going out, etc.). That said, I didn't slave away trying to get the ZCD jitter below 1uS -- I anticipated that it would be, just because there's nothing in the design to prevent it, so I wasn't surprised when it worked out that way. Best regards, Charles = Everything works if you let it. Corpus C. Redfish = ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chuck Forsberg WA7KGX c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 microseconds. But yes, given the terrible power factor of a lot of consumer loads, I suspect you could see a change in the phase of the voltage just due to the IR drop in the feeder and distribution, since the I isn't in phase with the E. The 15 year old refrigerator I just got rid of was 200W+ and had a PF of 0.50-0.60, which is pretty bad. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Simple AC mains zero-cross detector
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 transformer isolated and gives excellent results, is posted at ko4bb.com: http://www.ko4bb.com/manuals/download.php?file=05_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf The ZCD uses a small, dual-primary power transformer, two transistors, and a few diodes, resistors, and capacitors. It produces a ~100uS logic-level pulse at every positive zero-cross, the leading edge of which is predictably and stably related to the AC mains zero-cross. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 AC mains ZCD that is transformer isolated and gives excellent results, is posted at ko4bb.com: http://www.ko4bb.com/manuals/download.php?file=05_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf The ZCD uses a small, dual-primary power transformer, two transistors, and a few diodes, resistors, and capacitors. It produces a ~100uS logic-level pulse at every positive zero-cross, the leading edge of which is predictably and stably related to the AC mains zero-cross. Best regards, Charles 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 measurements that would satisfy a time-nut's curiosity, so if someone wants to Spice it or otherwise tear it apart, please do.. My use for the circuit was in a spot welder control; the output was used to sync and cycle a counter-driven trigger for an alternistor, all of which controlled the number of power line cycles that the welder transformer received for the weld. It worked well for me until I sold the whole contraption. Don't know whatever happened to it after the guy moved away from the area; never heard from him again. I hope it's still working. http://electronicdesign.com/analog/differential-line-receivers-function-analog-zero-crossing-detectors Dave M ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 DMTD is equally at home processing a 60 Hz sine wave. The rise time, bandwidth, and progressive stage gain issues are the same. 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. Again, just because you can does not mean you should. Bob On Dec 16, 2014, at 8:58 PM, Dave M dgmin...@mediacombb.net wrote: 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 AC mains ZCD that is transformer isolated and gives excellent results, is posted at ko4bb.com: http://www.ko4bb.com/manuals/download.php?file=05_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf The ZCD uses a small, dual-primary power transformer, two transistors, and a few diodes, resistors, and capacitors. It produces a ~100uS logic-level pulse at every positive zero-cross, the leading edge of which is predictably and stably related to the AC mains zero-cross. Best regards, Charles 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 measurements that would satisfy a time-nut's curiosity, so if someone wants to Spice it or otherwise tear it apart, please do.. My use for the circuit was in a spot welder control; the output was used to sync and cycle a counter-driven trigger for an alternistor, all of which controlled the number of power line cycles that the welder transformer received for the weld. It worked well for me until I sold the whole contraption. Don't know whatever happened to it after the guy moved away from the area; never heard from him again. I hope it's still working. http://electronicdesign.com/analog/differential-line-receivers-function-analog-zero-crossing-detectors Dave M ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Simple AC mains zero-cross detector
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 measurements that would satisfy a time-nut's curiosity, so if someone wants to Spice it or otherwise tear it apart, please do. 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 characterized in relation to the AC mains zero cross. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
