This article describes the interaction design of my kitchen timer. The designers have paid attention to how the timer will be used as well as to how it works, and despite ignoring the conventional wisdom that eschews modal interfaces—the timer has several modes and overloads every button—the interaction is natural and easy to use.
In a modal interface, gestures have different effects depending on the current mode. Modal interfaces are often difficult to use because users focus on the task they want to perform rather than on the current mode of the interface; when users want to perform a task in one mode but the interface is actually in another mode, tapping a key or pushing a button can produce unexpected and confusing results.
A commonly cited example of a modal design is the multi-function digital watch. Typical digital watches have several modes, including time and date (the default mode), stopwatch and countdown timer. Digital watches also have a small number of control buttons that perform different functions depending on the current mode of the watch. For example, in stopwatch mode, the top-right button might reset the stopwatch; in time-and-date mode, the same button might activate the backlight. Because the top-right button is overloaded, users can inadvertently reset the stopwatch when they intended to activate the backlight, which is an unintended and undesirable outcome.
The advantage of dividing the functions of a device into modes and overloading its buttons is that the device needs fewer buttons, which, in turn, reduces the size of the device. Making devices such as digital watches smaller is often a more desirable goal than modeless operation. Modal designs are not always difficult to use; they can work well when the transition between modes is clear and seems natural, and when the button overloading makes sense in the context of the task. And this is why my kitchen timer works so well.
My kitchen timer counts down to zero from a user-set duration in hours and minutes or minutes and seconds. A switch on the back of the timer toggles between the two modes. The timer handles mode changes gracefully by remembering the duration last used in each mode. For example, if the timer displays 02:35 in minutes and seconds when the user switches to hours and minutes mode, the timer sets itself to 02:35 when the user switches back to minutes and seconds mode. The letters H and M and M and S indicate the mode clearly on the display:
Two buttons set the duration of the timer. Pushing the H/M button adds one hour to the duration in hours-and-minutes mode, and adds one minute in minutes-and-seconds mode. Similarly, the M/S button adds one minute to the duration in hours-and-minutes mode, and adds one second in minutes-and-seconds mode. Pushing both buttons at the same time resets the duration to 00:00.
The H/M button is overloaded with two functions:
The M/S button is also overloaded with two functions:
However, each button seems like it has only one function:
Although the H/M button is above the M/S button, the H/M button is slightly to the left of the M/S buttons. This suggests that the left button increments the digits to the left of the colon, and that the right button increments the digits to the right of the colon. Aligning the H/M and M/S buttons horizontally would improve the design by strengthening the mapping between the buttons and the digits.
After setting the duration, pushing the Start/Stop button starts the countdown. Pushing the Start/Stop button then toggles between pausing and resuming the countdown. When the countdown reaches 00:00, the timer sounds an alarm. Pushing the Start/Stop button stops the alarm.
My kitchen timer is also a stopwatch. The stopwatch counts up in hours and minutes or minutes and seconds, depending on the position of the switch on the back of the timer. The Start/Stop button starts the stopwatch as well as the timer. Although the Start/Stop button is overloaded, the overloading works in a natural way that makes sense: when the display reads a non-zero duration set with the H/M and M/S buttons, pushing the Start/Stop button starts the countdown timer; when the display reads 00:00, pushing the Start/Stop button starts the stopwatch. Pushing the Start/Stop button pauses the stopwatch; pushing it again resumes the stopwatch.
Although the Start/Stop button is overloaded with five functions:
this button seems like it has only two functions:
Because it seems natural to count up from zero and to count down from a non-zero duration, the overloading of the Start/Stop button also seems natural.
The designers of my kitchen timer have also paid attention to the environment in which it will be used: the sides of the timer are rubberized for a good grip, which is especially useful with wet hands. Furthermore, the versatile clip on the back of the timer enables users to place the timer in three positions: the magnet on the clip attaches the timer to fridge doors; the spring-loaded clip pegs the timer onto clipboards and belts; and the small metal bar that drops down when the clip is opened forms a table-top stand.