Why not just use one of these: Analog Devices ADE7753 - Has an application note AN564 with a complete design. There is also an evaluation board w/ schematic ADE7753EB
----- Original Message ---- From: Randall Nortman <[EMAIL PROTECTED]> To: gEDA user mailing list <[email protected]> Sent: Friday, May 2, 2008 1:21:32 PM Subject: Re: gEDA-user: Using 60Hz mains frequency for timing? Thanks very much to all who responded... and so quickly. I should have included more information on the application -- This is for building a power meter (watts and watt-hr) for measuring power consumption of particular circuits as well as the whole house (but not for billing purposes -- just informational). To give you an idea of what I mean by "low resolution", The timing will affect primarily the watts output, which is calculated as 15-second averages. It is also somewhat important that the watt-hr accumulation correlate with the *monthly* energy bill, which comes from the utility's meter on the outside of the house. I am sure that older electromechanical meters rely on the 60Hz signal for timing; I'm not sure what newer digital ones do. It sounds to me like my 15-second periods will perhaps be slightly more stable with the crystal, but the 60Hz should get close enough. For the monthly comparison with the utility power meter, it sounds like the long-term stability of the 60Hz is likely to be far better. I get either signal for "free" already (with good glitch filtering on the zero-crossing detect), so neither is more convenient. Given all that, I think I will go for the 60Hz signal. Or maybe if I have some spare time I'll test one against the other -- assume the 60Hz is stable on a daily basis and check the drift of the crystal against it. Thanks for all the info. -- Randall _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
