■ PHOTO 6. Close-up view of the LCD timer
hardware. Simplicity is the key to be able to
run an electronic circuit with such a tiny
amount of energy.
potted plants required to form a battery.
As mentioned, the hardware design is
built around the MSP430F230
microcontroller. It has an impressive ultra
low-power operation mode and a Dual-In-Line (DIP) package very suitable
to the hobbyist (see Photo 6).
The MSP430F2013 lacks an LCD controller, so this
task is done by software with the help of a watchdog
working as an interval timer. The VIKAY LCD I1045 is a
two digit static LCD, which means each segment must be
driven by a dedicated I/O line. Since the number of
available outputs in the MSP430F2013 is quite limited,
only the least significant digit is driven requiring port P1 of
the microcontroller to be dedicated to drive the LCD.
The main advantage of static drive is that it is simple
to implement. You only have to worry about which
segment line to turn on and off, while activating the
common signal all the time. Another advantage is that
voltage levels can go from rail to rail and do not require
multiple intermediate levels as is needed when driving
■ FIGURE 3. Schematic of the LCD
timer based on the ultra-low power