Alan Parekh has a great web page for gadgets that have been hacked. One of Alan’s projects was featured recently in the Gadget Freak column of Design News, both in print and online. The project is titled “Measuring time with meters” (no, there is not a problem with units in that title). The meters are analog multi-meters, and Alan has created a circuit that drives the needles to display the time.
The circuit is based on a PIC microcontroller that uses three PWM outputs to drive the needles through a calibrating resistor. The project has many neat features:
On startup, you can calibrate each meter individually to set the full scale PWM value. This is then stored in non volatile memory so re-calibration is never needed again.
Alan liked the jumpy look of a quartz watch, so by default the second hand (second needle?) moves once per second. However you can fit a jumper to the PIC and instead update the second hand 10 times per second, resulting in the smooth motion typical of a mechanical movement.
The circuit is designed to run on a 9-12V wall wart transformer, but includes a4.5V battery to preserve the time in case of power failure. The PIC can detect power failure and reduces power to extend battery life.
Three switches allow you to set the values of the hour, minute, and second needles.
Alan has created custom scales for the meters.
The while thing is displayed in a giant version of a Simpson 260 multimeter case that Alan created on a CNC machine.
I like this project a lot for its attention to detail — especially the case that everything is mounted in. Unfortunately the video link is incorrect in the Gadget Freak column. This is the correct link. The article includes great instructions on how to build your own. Alan sells a few kits on his WWW page, maybe he’ll offer kits and custom Simpson cases for his analog clock also.
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