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 > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/7fa9d194-34e0-4aa4-9348-ec19fd1051f6%40googlegroups.com.
