Len sent in this great clock (schematic at the bottom of the site) – “It’s actually a pretty simple circuit. The clock is based on an Atmel AT89C2051 microcontroller. The software in the microcontroller handles the count for the time. It “talks” to a 4 channel Digital to Analog converter to derive the voltage to position the needles on the three meters. The outputs of the D2A converters are buffered with a quad amp. Otherwise the current draw of the 1ma meters would exceed the D2A converter. A Dallas DS1307 generates an accurate 1hz timing signal and also backs up the time setting in the case of a power failure. It’s very cool to watch the seconds meter raise as a minute progresses and them fall to zero again. The clock runs in a 24 hour mode.” – Link.
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