Symon wrote: ...> Check out > http://www.saultstar.com/webapp/sitepages/content.asp?contentID=70613&catname=Local+News > A small town in Canada where everyone's clocks gained 10 minutes. > Cheers, Syms.... Considering the natures of the affected clocks, my bet is on some sort of noise. Not all clocks were affected, only those that count zero crossings and have no flywheels. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
60 Hz Hum removal
Started by ●July 1, 2004
Reply by ●July 2, 20042004-07-02
Reply by ●July 2, 20042004-07-02
JA [Fri, 02 Jul 2004 10:25:56 -0400]: >... Tell that to the motor on my phonograph turntable! Very odd since most turntables made in the last 30 years have used a DC motor. I remember the days of those AC motors, where you were given two pulleys: one for 60 Hz and another for 50Hz. But then again, you did write "phonograph..." !! Hi-Yo! As a youngster, that's where I got most of my parts - discarded "phonograph turntables". -- 40th Floor - Software @ http://40th.com/ iPlay : the ultimate audio player for iPAQs mp3, ogg, mp4, m4a, aac, wav, and then some
Reply by ●July 2, 20042004-07-02
"Symon" <symon_brewer@hotmail.com> wrote in message news:2klgrqF3sm5rU1@uni-berlin.de...> But sometimes they do. > Check out >http://www.saultstar.com/webapp/sitepages/content.asp?contentID=70613&catname=Local+News> A small town in Canada where everyone's clocks gained 10 minutes. > Cheers, Syms.Yup. My family comes from Blind River (small world!), and I can confirm that it is just the sort of town where the power line frequency might shift for a while, and they would have a lot of old clocks built on single-phase induction motors. -- Matt
Reply by ●July 2, 20042004-07-02
hel@40th.com wrote:> JA [Fri, 02 Jul 2004 10:25:56 -0400]: > >... Tell that to the motor on my phonograph turntable! > > Very odd since most turntables made in the last 30 years have > used a DC motor. I remember the days of those AC motors, where > you were given two pulleys: one for 60 Hz and another for 50Hz. > But then again, you did write "phonograph..." !! Hi-Yo! As > a youngster, that's where I got most of my parts - discarded > "phonograph turntables".30 years? You're thinking about new ones! I bought mine in 1956. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●July 2, 20042004-07-02
Matt Timmermans wrote:> "Symon" <symon_brewer@hotmail.com> wrote in message > news:2klgrqF3sm5rU1@uni-berlin.de... > >>But sometimes they do. >>Check out >> > > http://www.saultstar.com/webapp/sitepages/content.asp?contentID=70613&catname=Local+News > >>A small town in Canada where everyone's clocks gained 10 minutes. >>Cheers, Syms. > > > Yup. My family comes from Blind River (small world!), and I can confirm > that it is just the sort of town where the power line frequency might shift > for a while, and they would have a lot of old clocks built on single-phase > induction motors. > > -- > MattAccording to the article, motor-driven clocks weren't among the affected ones. The only ones cited were electronic. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●July 3, 20042004-07-03
"Jerry Avins" <jya@ieee.org> wrote in message news:40E60ECA.1050500@ieee.org...> According to the article, motor-driven clocks weren't among the affected > ones. The only ones cited were electronic.They also mention an electric "dial hand clock" that was affected, and I was thinking that "electrically powered digital" meant mechanical flipping numbers driven by a synchronous induction motor, which matches a lot of clock radios. It doesn't match stoves or microwaves, though, so those would be the sort of clocks you're talking about, I guess -- electronic, but without crystal oscillators. I didn't know anyone actually made them like that. It seems that both types were affected, but it's hard to tell from the article. I'm sure the Sault Star will get to the bottom of it eventually.
Reply by ●July 3, 20042004-07-03
The rule for power companies is not to keep the frequency solid at 60 Hz but to get the right number of cycles in a day, precisely for the clock problem. If you run a regular motor-driven clock next to an atomic one, you can see a regular gain and loss pattern each day of a few seconds. -- Ron Hardin rhhardin@mindspring.com On the internet, nobody knows you're a jerk.
Reply by ●July 3, 20042004-07-03
If your audio segment is long enough and you are able to determine a 60 Hz hum, it's possible to determine the phase of the 60 Hz component and remove it by adding an inverted 60 Hz component. Many "60 Hz" hums have strong harmonic components, so you'll find yourself wanting to remove the 120 Hz as well. Tim Wescott wrote:> Rob Hutchinson wrote: > >> What is the preferred method for removing 60 hz hum from a signal without >> wiping out signal info around 60 hz? A 60 hz notch filter would not be >> useful because it would attenuate the signal as well. I'm interested in >> doing this for sampled data, so all filtering would be done in the >> digital >> domain. >> Thank you in advance, >> Rob >> >> > > Your signal processing algorithm won't be able to tell the hum from the > real data -- you're stuck with either a really narrow 60Hz notch (which > you can do digitally if you're really careful about numeric precision) > or trying to remove the hum before you acquire. Neither of these is a > good prospect, but there you are. > > Perhaps you should move to Germany, or Brazil? Then you'll only have to > worry about 50Hz, or 25 :). >
Reply by ●July 4, 20042004-07-04
hel@40th.com wrote:> JA [Fri, 02 Jul 2004 10:25:56 -0400]: > >... Tell that to the motor on my phonograph turntable! > > Very odd since most turntables made in the last 30 years have > used a DC motor.But the stroboscopic light for adjusting the speed is based on the AC frequency -- granted, it typically has the tracks for both 50 and 60Hz, and for both 33.33 and 45 RPM. You'd have to just realize by ear that the correct adjustment is given by the 60Hz and not 50 as you thought (which should be more than obvious even for someone tone deaf :-)) So, is it only in Argentina that they use 220V / 50Hz? I know in other parts of South America they use 110 / 60. Carlos --
Reply by ●July 5, 20042004-07-05
On Sun, 04 Jul 2004 10:53:11 -0400, Carlos Moreno <moreno_at_mochima_dot_com@xx.xxx> wrote:>hel@40th.com wrote: >> JA [Fri, 02 Jul 2004 10:25:56 -0400]: >> >... Tell that to the motor on my phonograph turntable! >> >> Very odd since most turntables made in the last 30 years have >> used a DC motor. > >But the stroboscopic light for adjusting the speed is based >on the AC frequency -- granted, it typically has the tracks >for both 50 and 60Hz, and for both 33.33 and 45 RPM. You'd >have to just realize by ear that the correct adjustment is >given by the 60Hz and not 50 as you thought (which should be >more than obvious even for someone tone deaf :-))All of the ones I've seen have used cystal controlled strobes. (E.g. Technics SP10, SL1200, etc.) Regards, Allan.
