I am working on a simple 24-hour clock based on the CD4017. To reset when the clock reaches the 24th hour, two diodes are used to produce an "and" logic when the 2 digit and 4 digit LEDs receive a high output from the CD4017. The output from these diodes are connected to the reset pins of both CD4017 chips.
What I have found happens in practice is that the U-H10 chip resets as expected, but the U-H01 chip does not. I imagine this could be due to a delay in the signal due to differences in trace lengths (maybe 10-20mm) and or placements somehow creating a tiny RC effect. (One has more vias than the other.) I tried adding a small cap, shorting resistors R138 and R6, as well as removing R18 (on an etched PCB, not a breadboard.) I also checked the reset (pin 15) of U-H01 and it does not APPEAR to be shorted to ground.
Has anyone else faced a similar problem? Ideas?
NOTE For those unfamiliar with the CD4017, the reset is high, not low. From the TI datasheet "A high RESET signal clears the counter to its zero count." Therefore a monostable circuit that is waiting for a falling edge voltage to trigger will not work in this application without using an inverter.