On Thu, Feb 16, 2012 at 12:37 PM, Rob Clarke <crock@clarke-family.org.uk> wrote: > Wow - so many options. I like the option of a single chip solution from > Gerrit as it doesn't require opening the PSU or attaching or hooking up to > mains voltages. Incidently, the MAX machine used a 555 to generate the TOD > signal, as Uz speculated. There used to be an 8-pin DIP that was commonly used in the 1970s for generating 60Hz using a 32768Hz watch crystal. These days, it's often done with an 8-pin PIC or AVR. I don't remember which part I used, but I made one about 5 years ago, since I needed to run an 8051-based clock off of DC and the design had a diode and a 74HC14 off of the low-voltage AC side of the rectifier. I remember it being moderately accurate. For that matter, unless you are using your PET as a desk clock, a 555 is probably accurate enough for casual use, and it's hard to get cheaper than that. -ethan Message was sent through the cbm-hackers mailing listReceived on 2012-02-16 18:00:16
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