I was wondering why the KABtronics clock does it as a divide by 10 stage and then a divide by 6 stage, and I guess we just got the answer....
A divide by 10 needs only 2 inputs (8 and 2) and doesn't pass through any intermediate states which could cause a reset because of transients, and the same with divide by 6 (4 and 2).
I'm not sure how much of the KABtronics circuit I can post here without inducing copyright wrath and crossing the boundary to unfair behaviour. Suffice to say, that you're pretty close to what I saw in the manual.
I actually have their assembly instructions off the KABtronics website to get a feel for how they built theirs. Much more reliable using gates to dictate the operation of the counters. I can always add an extra flip-flop to the end and install some gates, but I want to avoid borrowing too much from someone else's design as this was supposed to be a logic exercise for myself.
I'm about to pull my hair out. I built the circuits the guys at KABtronics used to a tee. The divide-by-10 circuit produces a perfect 6.00Hz signal on the Oscope. The divide-by-6, however, STILL produces a 1.04Hz signal with their reset logic. I don't get it. The scope can measure frequencies lower than one, but is there any chance it could be wrong? I'm really at a loss here.
Okay, so i may have overreacted a bit. Also I think the oscilloscope might be lying. I've been leaving the clock running overnight to test accuracy, and interestingly, at night it seems to slow a little while during thr day it picks up. Additionally, so far for two days the amount of time it has been over or under (in seconds) has been roughly equal. I should mention that I only have my phone and computer as time references, and I've read that those may not always be perfect. I'll post a new thread showing off my build with pictures here soon, as it's nearing completion. And again, thanks much to Ty and Ian for the help with this project!
1 year 7 months ago - 1 year 7 months ago#7548by Ian
This is a known effect for mains driven time sources. The frequency varies slightly with the load on the network, and the utility providers only guarantee average accuracy over a 24 hour period, but not instantaneous accuracy.
This is a good read: url=https://en.wikipedia.org/wiki/Utility_frequency]https://en.wikipedia.org/wiki/Utility_frequency[/url]
I was trying to find a display of the frequency variations, but it seems that in the US, this varies a lot by region and area. I come from a small country where there is a single grid, but on large, decentralised grids, this is up to the local utility company.
I have also been reading that the frequency regulation has been relaxed in the US (since 2011), and there is no longer a regulatory requirement to guarantee 60Hz.
I'm getting the impression that the Internet is a better source of time than the power socket....