OK, I wasn't paying attention as the info passed by. 'Xactly how is this huge signal introduced to the PC? I remember something about a voltage divider off the hot side of the line, put on an input pin of the PC's com port and then somehow timestamped and put on a data file. Howsat done again? Sorry to be so lame, but I really wasn't paying attention. Don
Hi Don, What I did in the quick PC experiment was feed the output of a 5 VAC wall-wart transformer through 1k to DCD (pin1) of the PC's serial port. Probably not wise to voltage divide raw mains power and send it to a serial port. If using a high-z input of a microcontroller, the doc2508.pdf app note that you found shows both sides of mains going through 1M resistors. There was concern that noise would cause false triggering. There are a variety of hardware-only or software-only solutions to this concern. Bill found a robust ZCD circuit if you need a hardware solution. Time-stamping samples is the basis of software solutions. Note looking for a sample 990 to 1010 milliseconds from the last sample is a nice way get 1PPS from 60 Hz. This is more immune to noise than traditional division-by-60 techniques. As it turns out, I've gotten clean 1PPS data with no h/w or s/w filtering so maybe this whole noise concern is overblown. /tvb _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
