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.
This photo does not show the meters with the updated scales that will
reflect the time digits and not the original DB scale.
Here is the clock built on a circuit board.
Photo showing the enclosure I bought for the meter clock and the meter mount. (The enclosure is a pencil box bought from an office supply store.)
A view from the front of the clock. The meter scales have been updted for time display.
Another way I packaged the meter clock
Express PCB free software
|Copyright © 2004-2010, Len Bayles
|Feb 6, 2010