This is a multi-part message in MIME format. ------=_NextPart_000_0057_01CAC779.B1BB8FF0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Dario Greggio wrote: > circuit Yucc. It's inconvenient to only have the PIC see half the wave, but that can be dealt with in firmware. What I really don't like is the way the negative values are clipped. At the very least, D4 needs to be a zener diode. Allowing any appreciable current to flow thru the protection diodes can really mess up A/D readings. I have found this from experience, and the datasheet, especially for newer PICs, frowns on this too. Attached is a simple circuit that provides all the possible information to the PIC firmware and doesn't have any issues with clipping. For Vdd of 3.3V, this will tolerate input line voltage up to about 260V, assuming 220/6 stepdown ratio of your transformer. This should leave reasonable room for part tolerances, voltage range, etc, but still allow plenty of resolution with the PIC A/D. It also filters out spikes and frequencies that will cause aliasing. ------=_NextPart_000_0057_01CAC779.B1BB8FF0 Content-Type: image/gif; name="b.gif" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="b.gif" R0lGODlh2wEiAfcAMQAAAAEBAQICAgMDAwQEBAUFBQYGBgcHBwgICAkJCQoKCgsLCwwMDA0NDQ4O Dg8PDxAQEBERERISEhMTExQUFBUVFRYWFhcXFxgYGBkZGRoaGhsbGxwcHB0dHR4eHh8fHyAgICEh ISIiIiMjIyQkJCUlJSYmJicnJygoKCkpKSoqKisrKywsLC0tLS4uLi8vLzAwMDExMTIyMjMzMzQ0 NDU1NTY2Njc3Nzg4ODk5OTo6Ojs7Ozw8PD09PT4+Pj8/P0BAQEFBQUJCQkNDQ0REREVFRUZGRkdH R0hISElJSUpKSktLS0xMTE1NTU5OTk9PT1BQUFFRUVJSUlNTU1RUVFVVVVZWVldXV1hYWFlZWVpa WltbW1xcXF1dXV5eXl9fX2BgYGFhYWJiYmNjY2RkZGVlZWZmZmdnZ2hoaGlpaWpqamtra2xsbG1t bW5ubm9vb3BwcHFxcXJycnNzc3R0dHV1dXZ2dnd3d3h4eHl5eXp6ent7e3x8fH19fX5+fn9/f4CA gIGBgYKCgoODg4SEhIWFhYaGhoeHh4iIiImJiYqKiouLi4yMjI2NjY6Ojo+Pj5CQkJGRkZKSkpOT k5SUlJWVlZaWlpeXl5iYmJmZmZqampubm5ycnJ2dnZ6enp+fn6CgoKGhoaKioqOjo6SkpKWlpaam 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