- The switch is to select the mode, between displaying the current time, setting the current hour, and setting the current minute.
- The LED is a red-green LED, which displays the current time upon request. Green flashes mean 10, yellow 5, and red 1, so the time 5:28 would be displayed as YELLOW [PAUSE] GREEN GREEN YELLOW RED RED RED (5:10+10+5+1+1+1). It also adds an alternating red-green pattern to the time in the PM.
- The push button activates the display, bringing the controller out of sleep mode long enough to either blink out the current time, or update the time based on the mode select switch.
- MSP430G2101 controller (though any MSP430G2 controller with 1k+ of flash should work
- 32.768kHz quartz crystal. I happened to only have a 6pF one, instead of the more standard 12.5pF, but the crystal oscillator in the MSP430 can be adjusted in software to match either.
- perf board large enough to fit the controller
- 1 14 pin DIP3 socket
- 2x 120Ω resistors for the bicolor LED anodes
- 1 bicolor red-green LED
- 1 5mm LED panel mount
- 1 100μF and 1 0.1μF capacitor for power filtering on the perf board
- 1 2xAA battery clip
- 1 4k pull-up resistor for the reset pin
- 1 NO (normally open) push button
- 1 SPDT (single pole double throw) switch with center off position
- 1 gang box and blank cover
Update 9/17/2010: Fixed the error in the schematic, and it turns out this project has been reimplemented by one of my readers. :-)