Is there a way to edit a message after it is posted? On Friday, October 4, 2019 at 10:01:37 AM UTC-6, Jim KO5V wrote: > > Hi Robert, > HI Robert, > > Which OZ2CPU clock do you have? I just built 2, V1.08 clocks (ca > 2005-ish), running IN-18 tubes, and V5.8 firmware. Our mains frequency is > very flaky, and I was being slowly driven nuts by the clocks sometimes > gaining several seconds per day. Maybe the long-term average is fine, but I > can't seem to deal with it! > > The kits were designed to take a 50Hz, 60Hz or 1pps reference signal. I > found the DS3231 clock chip, which is compensated for temperature, and is > very accurate. It puts out a 32.768 kHz square wave, which when put through > a couple of flip-flops, gives a ~5V 1pps square wave (.5 sec on, .5 sec > off). The clocks have been accurate since I added this circuit. > > However, there is one "glitchy" thing: it takes exactly 39 seconds from > when the "set" button is pressed, for the seconds start counting. It's no > problem, I just have to set it for the next minute, and press the set > button at 21 seconds after the current minute starts. This delay is > consistent. > > I ordered a new PIC withe the latest firmware (V6.3, I think). A "slot > machine" effect was added to prevent cathode poisoning (it does this every > 10 minutes, which is a bit too often for me). With the new PIC, the 1pps > input does not cause the 39 second delay, and it keeps perfect time, but it > screws up the slot machine effect so each tube shows one number for 3 > seconds when it is supposed to be doing the tube-saving routine. It works > fine with the 60Hz reference. > > I have gone back to the original firmware, and am just living with the 39 > second set delay. I have added LDRs to the clocks, which gives them four > tube illumination levels. That should help with the tube life. > > I also have one of his two-tube B7971 clocks that has been running for > about 15 years. Since there are no seconds, I haven't noticed any error, so > no stress there! > > If you would like some details as to what I did to convert the clocks to > the 1pps reference, let me know. I invented nothing here, just combined the > work of other folks! > > Good luck. Jim > >> >> Finally, I have been thinking of replacing my now 40 year old handiwork >> with the OZ2CPU kit I assembled as it supports B-7971's. The design I >> followed uses the line frequency for time keeping. Unfortunately it tends >> to drift quite a bit during the day and any line noise can cause the time >> to change quite a bit. Also I am finding the whine from the multiplexed >> tubes bothers me more now than it did when I was younger. That tells me it >> is time to modernize. >> >> >> Robert >> >
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