Tag: PCB design
The slow ticking clock.
by Jae686 on Jan.18, 2012, under Electronics, Nixie Clock
And all was good. The latest version of the nixie clock survived it’s smoke test, and, as usual, I’ve let it powered for a while and then something quite awkward started to happen : The clock always got consistently late. Its was quite odd, since most of the PCB remained the same, except for the inclusion of the Nixie Power Supply and the re-positioning of several traces and components.
The fact that the failure is consistent leads me to believe that it should not be related to the Nixie’s HV PSU presence on the same PCB as the RTC. And the fact that the seconds are twice as slow (a consistent behavior) is clearly measurable.
After some digging, I’m inclined to believe that the root cause for the clock not behaving as expected was due to the pcb track re-routing. When re-routing the PCB traces, some traces passed very close the the RTC’s crystal pins. And yes, this is noted on Maxim’s RTC’s aplication notes.
Well, back to PCB etching!
Fixed design : GND guard ring around the RTC, and the traces were re-routed to avoid being close to the cristal.
