how to detect lower edge of sine wave at 100Hz..?

dani · Joined: 02 Jun 2004 Posts: 16 Location: Pakistan

Hi all,

I need to start a timer after detecting every lower edge of a ac standerd sine wave of 50HZ.

I have changed these waves to fully rectified sinewave.

..............................*........*.......... ..........................*.......*..............
.....................*........................*... ..................*.....................*........
................*................................. .*...........*...............................*...
.............*.................................... ....*....*......................................*.
.. --->..*............................................*<---................................-->...*
...here........................................... .......here................................here

can any one give me idea how to do this and if any one can share some sample code.

Regards

ljbeng · Joined: 10 Feb 2004 Posts: 205

Have you looked at the H11AA1? I use these. I get a 120hz pulse from a 60Hz 120Vac line. I get one pulse at all the zero crossings. The middle of that pulse would be the exact zero crossing point. I am not sure what you mean by "Lower Edge". Do you mean only the part of the sine wave that is below the line?