Post by thread:[OT]: Re: [PIC] Timer Tribulations

Vasile Surducan wrote: > > On Wed, 21 Feb 2001, Tony Nixon wrote: > > > You will find that the clock will drift one way or the other depending > > on temperature, so using the mains as a frequency source is much more > > accurate. > > You are certainly joking ! Or in your country mains frequency drift is > under 0.5% ... > > Vasile > Perhaps a bit of AC math about power consumption in a system as large as a state grid may reveal why power companies try to keep the frequency as stable as possible. I'm definitely no expert here, but I'll bet it is definitely in the power company's best interest. Upteen million clocks around the world wouldn't be using the principle if it was unreliable. -- Best regards Tony mICro's http://www.picnpoke.com spam_OUTsalesTakeThisOuTpicnpoke.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

The US is hooked up into a single power grid so that power can be shared from one region to another over long distances. In order to do this easily, it is necessary for all the generators not only to be producing the same frequency, but the same phase as well. AC motors and generators (which are pretty nearly the same thing) are a lot like stepping motors we are familiar with. For a given phase of the power, their rotors want to be in a corresponding physical position. If you tie two generators together that are not in phase, the one that's ahead will supply current to the one that's behind, which will act as a motor trying to catch up (which will also load down the one that's ahead, slowing it down). To do this, they will exchange current -- a lot of current, because they will want to do this as nearly instantaneously as they can. So the load is getting heavy, and someone goes to switch on another generator to handle the load, but it's out of phase. Humongous relays clang closed, and huge currents rush about as rotating machines as big as houses jump and buck and make the ground shake, and the lights dim. Actually what happens is circuit breakers take both generators off line before something breaks, and now the grid really is overloaded... Power companies pay a whole lot of attention to frequency and phase. They coordinate this, and keep the whole grid locked to very precise frequency standards. Sometimes when the load is heavy, they do get behind a few cycles, but later on when the load lightens, they speed up. If you observe an electric wall clock carefully and compare it to something like WWV, you may see it get a few seconds behind on a hot summer afternoon, but it will be caught up by the next morning. So the grid, at least in the US has great long-term stability, but only pretty good short-term. > {Original Message removed}

In Ukraine these clocks just don't work correctly. Currently we have the mains frequency at about 49.3 Hz, and if you assume the frequency is 50 Hz... :) Nikolai ---- Original Message ---- From: Tony Nixon <.....Tony.NixonKILLspam@spam@ENG.MONASH.EDU.AU> Sent: Thursday, February 22, 2001 23:49:33 To: PICLISTKILLspamMITVMA.MIT.EDU Subj: [OT]: Re: [PIC] Timer Tribulations {Quote hidden}> Vasile Surducan wrote: >> >> On Wed, 21 Feb 2001, Tony Nixon wrote: >> >> > You will find that the clock will drift one way or the other depending >> > on temperature, so using the mains as a frequency source is much more >> > accurate. >> >> You are certainly joking ! Or in your country mains frequency drift is >> under 0.5% ... >> >> Vasile >> > Perhaps a bit of AC math about power consumption in a system as large as > a state grid may reveal why power companies try to keep the frequency as > stable as possible. > I'm definitely no expert here, but I'll bet it is definitely in the > power company's best interest. > Upteen million clocks around the world wouldn't be using the principle > if it was unreliable. > -- > Best regards > Tony > mICro's > http://www.picnpoke.com > .....salesKILLspam.....picnpoke.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Nikolai Golovchenko wrote: > > In Ukraine these clocks just don't work correctly. Currently we have > the mains frequency at about 49.3 Hz, and if you assume the frequency > is 50 Hz... :) > > Nikolai It'll give you more time to relax ;-) -- Best regards Tony mICro's http://www.picnpoke.com EraseMEsalesspam_OUTTakeThisOuTpicnpoke.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

On Fri, 23 Feb 2001, Tony Nixon wrote: > Nikolai Golovchenko wrote: > > > > In Ukraine these clocks just don't work correctly. Currently we have > > the mains frequency at about 49.3 Hz, and if you assume the frequency > > is 50 Hz... :) > > > > Nikolai > > > It'll give you more time to relax ;-) > I don't know why, but you ( americans ) look more relax than we are... Even when you have painted the moon with coca-cola sign, you found it already painted in red... at 49,3 Hz Zdrasvuite Nicolai, Cheers Tony, Vasile -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Hey! All this talk about clocks and 50Hz/60Hz mains timing and getting crystal clocks accurate just gave me a clever idea! Using mains sync is probably the best for accuracy, but has problems due to needing to provide a mains supply and then insulate high voltages or use a transformer etc. Just not practical for a battery powered PIC device on the wall. So how about this: Every time I use a high gain input on some circuit and put the cro on it there is always some 50Hz mains freq clearly visible on the signal. Yes even on battery driven circuits. Seems the average house has quite enough mains driven devices and mains wires running through all the walls that there is a very definite 50Hz/60Hz RF signal everywhere in suburbia. So... How about a simple two transistor high-gain amp (or op amp) tuned for about 50Hz. This could be fed into the PIC pin. Sure there would be some ocassional false triggers but the PIC could be smart enough to log input triggers in software and "decide" which are the real ones based on the general timer period which is always known. If done correctly you could have a battery powered PIC device anywhere in your home, mains sync'ed and running with perfect time accuracy. And never have to actually connect it TO the mains. So this is the point where some smartie normally says they already thought of it and have been making them for years... ;o) -Roman Tony Nixon wrote: > > > > You will find that the clock will drift one way or the other depending > > > on temperature, so using the mains as a frequency source is much more > > > accurate. > > > > You are certainly joking ! Or in your country mains frequency drift is > > under 0.5% ... -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Nikolai Golovchenko wrote: > > In Ukraine these clocks just don't work correctly. Currently we have > the mains frequency at about 49.3 Hz, and if you assume the frequency > is 50 Hz... :) > > Nikolai Ha ha! So they are ripping you off 0.7Hz!! You are getting less than what you pay for, I wonder if that applies, seriously??? :o) -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Vasile Surducan wrote: {Quote hidden}> > On Fri, 23 Feb 2001, Tony Nixon wrote: > > > Nikolai Golovchenko wrote: > > > > > > In Ukraine these clocks just don't work correctly. Currently we have > > > the mains frequency at about 49.3 Hz, and if you assume the frequency > > > is 50 Hz... :) > > > > > > Nikolai > > > > > > It'll give you more time to relax ;-) > > > I don't know why, but you ( americans ) look more relax than we are... > Even when you have painted the moon with coca-cola sign, you found it > already painted in red... at 49,3 Hz > > Zdrasvuite Nicolai, > Cheers Tony, > > Vasile Ha ha! Friendly competition!! :o) Hey, I just realised, the Coca Cola sign already IS red!! Is that telling us something??? ;o) -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Well, isn't Tony from Australia? :) I guess people in California are supposed to be most relaxed ... for a number of reasons... :) Let the light be! Nikolai ---- Original Message ---- From: Vasile Surducan <vasilespam_OUTL30.ITIM-CJ.RO> Sent: Friday, February 23, 2001 10:17:34 To: @spam@PICLISTKILLspamMITVMA.MIT.EDU Subj: [OT]: Re: [PIC] Timer Tribulations {Quote hidden}> On Fri, 23 Feb 2001, Tony Nixon wrote: >> Nikolai Golovchenko wrote: >> > >> > In Ukraine these clocks just don't work correctly. Currently we have >> > the mains frequency at about 49.3 Hz, and if you assume the frequency >> > is 50 Hz... :) >> > >> > Nikolai >> >> >> It'll give you more time to relax ;-) >> > I don't know why, but you ( americans ) look more relax than we are... > Even when you have painted the moon with coca-cola sign, you found it > already painted in red... at 49,3 Hz > Zdrasvuite Nicolai, > Cheers Tony, > Vasile -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

They rip us anyway! Usually houses don't have gas, heat or water counters. So everyone pays an "average" rate relative to apartment size. I heard the tenants of an apartment house installed the counters, and the actual payment should have been something like 20% less. But no one lets them pay less!! Seriously, the problem with low frequency, as far as I know, deals with overloaded power system. There are shortages of fuel, etc... And also someone decided to shut down the Chernobyl nuclear station. :) Nikolai ---- Original Message ---- From: Roman Black <KILLspamfastvidKILLspamEZY.NET.AU> Sent: Friday, February 23, 2001 13:09:22 To: RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU Subj: [OT]: Re: [PIC] Timer Tribulations {Quote hidden}> Nikolai Golovchenko wrote: >> >> In Ukraine these clocks just don't work correctly. Currently we have >> the mains frequency at about 49.3 Hz, and if you assume the frequency >> is 50 Hz... :) >> >> Nikolai > Ha ha! So they are ripping you off 0.7Hz!! > You are getting less than what you pay for, > I wonder if that applies, seriously??? :o) > -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Vasile Surducan wrote: > I don't know why, but you ( americans ) look more relax than we are... > Even when you have painted the moon with coca-cola sign, you found it > already painted in red... at 49,3 Hz > > Zdrasvuite Nicolai, > Cheers Tony, > > Vasile Ozzie mate :-) -- Best regards Tony mICro's http://www.picnpoke.com spamBeGonesalesspamBeGonepicnpoke.com -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu

Roman Black wrote: > > Hey! All this talk about clocks and 50Hz/60Hz mains > timing and getting crystal clocks accurate just > gave me a clever idea! > > Using mains sync is probably the best for accuracy, I thought about this ages ago, but I wonder how many 'ticks' get corrupted when electric motors, welders, etc. etc. are started and stopped. -- Best regards Tony mICro's http://www.picnpoke.com RemoveMEsalesTakeThisOuTpicnpoke.com -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu

Tony Nixon wrote: > Roman Black wrote: > > > > Hey! All this talk about clocks and 50Hz/60Hz mains > > timing and getting crystal clocks accurate just > > gave me a clever idea! > > > > Using mains sync is probably the best for accuracy, > > I thought about this ages ago, but I wonder how many 'ticks' get > corrupted when electric motors, welders, etc. etc. are started and > stopped. Thats probably why those old clocks had little flywheels in them <G>. They only tracked the average frequency, not the instantaneous one. As if anyone would notice the cumulative 1000/60 error when their alarm clock goes off. R -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu

Robert Rolf wrote: > > Tony Nixon wrote: > > Roman Black wrote: > > > > > > Hey! All this talk about clocks and 50Hz/60Hz mains > > > timing and getting crystal clocks accurate just > > > gave me a clever idea! > > > > > > Using mains sync is probably the best for accuracy, > > > > I thought about this ages ago, but I wonder how many 'ticks' get > > corrupted when electric motors, welders, etc. etc. are started and > > stopped. > > Thats probably why those old clocks had little flywheels in them <G>. > They only tracked the average frequency, not the instantaneous one. > As if anyone would notice the cumulative 1000/60 error when their > alarm clock goes off. I guess you could create a similar flywheel in software. Keep track of the 50Hz signal and if a valid signal change occurs outside a hysteresis point, ignore it. Can also be used to provide a timebase for brief power outages. -- Best regards Tony mICro's http://www.picnpoke.com RemoveMEsalesEraseMEEraseMEpicnpoke.com -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu

On Mon, 26 Feb 2001, Tony Nixon wrote: > Robert Rolf wrote: > > > > Thats probably why those old clocks had little flywheels in them <G>. > > They only tracked the average frequency, not the instantaneous one. > > As if anyone would notice the cumulative 1000/60 error when their > > alarm clock goes off. > > I guess you could create a similar flywheel in software. Yeah, but don't hit any breakpoints while you're simulating or your code will crash! -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu

Scott Dattalo wrote: > > I guess you could create a similar flywheel in software. > > Yeah, but don't hit any breakpoints while you're simulating or your code will > crash! Lose it's momentum don't you mean ;-) -- Best regards Tony mICro's http://www.picnpoke.com EraseMEsalesspamspamBeGonepicnpoke.com -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestKILLspammitvma.mit.edu

Tony Nixon wrote: > > Roman Black wrote: > > > > Hey! All this talk about clocks and 50Hz/60Hz mains > > timing and getting crystal clocks accurate just > > gave me a clever idea! > > > > Using mains sync is probably the best for accuracy, > > I thought about this ages ago, but I wonder how many 'ticks' get > corrupted when electric motors, welders, etc. etc. are started and > stopped. That's why you use software correction to make up for missed ticks, and only allow a small window for tick timing. It should self-correct given that it will receive 100 ticks/second. -Roman -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads