This one is very good, i have assembled it myself:
http://www.dextrel.net/diyzerocrosser.htm
Works very well with a very big voltage range, and it´s isolated. Only
disadvantage is that it generates 120Hz output, but I think you can
easily change that (turning the bridge rectifier into a half-wave
rectifier).
Daniel
Em 09/02/2014 19:34, Tom Van Baak (lab) escreveu:
It depends of your goals. If you want a 60 Hz time/frequency standard then
using a mains disciplined oscillator is good. Like AN12 shows.
But if your goal is to measure mains itself, warts and all, then measure mains
as it is, not a pure oscillator tied to mains by PLL or FLL.
See this Atmel app note: http://www.atmel.com/images/doc2508.pdf
Also: http://leapsecond.com/pages/ac-detect/
/tvb (i5s)
On Feb 9, 2014, at 12:04 PM, "M. Simon" <msimon6...@yahoo.com> wrote:
I kind of like the synchronized oscillator on page 6 of this pdf
http://cds.linear.com/docs/en/application-note/an12fa.pdf
They claim good results. I may have to build one and see.
Engineering is the art of making what you want from what you can get at a
profit.
On Sunday, February 9, 2014 7:44 PM, Chris Albertson
<albertson.ch...@gmail.com> wrote:
All you need to monitor line frequency is a small transformer connected to a
computer's DCD pin on a serial port. You can get fancier and use comparator,
opto isolation and so on but a simple 5V transformer is enough. This takes
advantage of the electronics inside the RS232 port that is designed to handle
positive and negative voltages up to about +/- 12 volts.
Then the linux pulse per second driver will time stamp and log every cycle with
the internal clock. It is accurate to a couple microseconds.
Don't worry about line noise because that is what you are measuring and it
averages out after a few cycles. You might try a >60Hz RC filter to remove
noise but I think to do any better you will have to treat the signal as if it were
audio frequency. So scale it to 1 volt peak to peak and read it with an audio
interface and then use an FFT. But the transformer on the DCD pin of any
normal computer with the Linux PPS driver works. People are doing just fine with
the simple transformer and time stamping the transitions. And then it is just
pure luck that Linux will already do this out of the box.
On Sun, Feb 9, 2014 at 5:53 AM, M. Simon <msimon6...@yahoo.com> wrote:
This probably came up during the recent discussion of Line Frequency Monitoring
but I may have missed it.
Does any one have a circuit (tested - operational) for monitoring line
frequency? I'd like something that checks zero crossing so that it is
relatively insensitive to line voltage variations.
Simon
Engineering is the art of making what you want from what you can get at a profit.
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Chris Albertson
Redondo Beach, California
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