December 2004, Issue 173

H8/38024F-Based Programmable Timer

OPERATING MODES

The timer counts in one of three modes. If you press the Start/Stop button after it’s first turned on, the timer begins counting up.  If the Minutes and Seconds up and down buttons are used to set a nonzero time before pressing the Start/Stop button, it counts down and beeps twice when done. The final mode involves selecting a stored program consisting of a preprogrammed set of times that are used in sequence.

A stored program (time set) can be as long as 20 time steps. You can store up to eight programs. Each step can be from 1 s to 99 min. and 59 s. To save programs, flip the Run/Program switch to Program, and then use the Set up and down buttons to select the set number you want programmed. The Step up and down buttons select which time step to change. The Minute and Second up and down buttons select the desired time interval; they automatically repeat when held down for more than 0.5 s. Use the On/Off/Clear button to set the current time to zero. Intermediate steps can be set to zero and used as placeholders. These won’t show up in Run mode. Changes are saved as soon as they are made, thereby considerably simplifying the user interface.

Each time the Set or Step number changes while in Program mode, they’re displayed briefly. Pressing the Start/Stop button redisplays them, making it easy to keep track of the current step.

After all of the desired time steps and sets are entered, you execute them by flipping the switch back to Run. Any non-empty sets now can be selected with the Set up and down buttons, and the first nonzero time step will appear. The Step up and down buttons will sequence through all nonzero steps of the selected set. The preprogrammed time for the current step also can be adjusted in Run mode with the Minute and Second up and down buttons, although the change won’t be stored permanently.