"It's not even a schematic error." I disagree: - you want your schematic to be consistent, in this case it's clearly not as most parts display their ground/power pins connected, except the MAX232A. - you want it to be unambiguous: obviously, it's not. - if you work with multiple voltage levels (but even if you don't), as does this design, missing the ground/power pins just means you have an incomplete schematic. You can't "debug" a product if you don't know what the voltages are supposed to be, even more when you know that in parts the schematic doesn't follow datasheet recommended values..
"And as Pete pointed out, the HV5530's work down below 5 volts, so no level shifters are necessary. This is not a design problem." Ah, so when you design things out of spec, as long as someone says it's fine, you don't have to worry? Of course this is a design problem: here's the datasheet of the HV5530: http://ww1.microchip.com/downloads/en/DeviceDoc/HV5530%20C072313.pdf In there, you'll see the recommended operating conditions: VDD Logic voltage supply MIN 10.8V MAX 13.2V Just because it works for some samples of the HV5530, it doesn't mean it'll work for all if you don't adhere to the datasheet. Note that this is actually fine in this clock, but not using a level shifter is not: VIH Input high voltage MIN VDD -2.0 MAX VDD 12 - 2 = 10, which is not 5V (or a bit lower) that the PIC will output as high. You can do this of course, but then you shouldn't be surprised if it fails, randomly. Or it may fail if you replace the part with one from a newer batch, where a different factory process was used. Now, I'm not saying Jeff didn't make great clocks. I'm just defending good engineering practices in general. He may well have made some decisions after careful testing, etc. -- 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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/ba1f00ed-f839-4982-80a4-347a2b83619b%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
