Despite modern clocks and watches having screens, when we think of electronic clocks we think of classic digital clock numbers. The boxy, segmented display that we can imitate with matches, toothpicks, and crayons just as easily as with an old-timey watch.
Here, we’ll be looking at this classic design — also known as the 7-segment design — for digital clock numbers a bit more closely.
The Elements of a Digital Clock Number
All digital clocks will have some variation in the design of their numbers. Manufacturers love putting their own spin on things. This can be from an angle of aesthetic design or to implement cost-saving measures. In any event, the digital clock numbers following a 7-segment design will have some similarities.
7 Segments
It should come as no surprise that digital clock numbers that follow the 7-segment design have… well, 7 segments.
Each of the seven segments is given a letter as a name, A through G. The top segment is labeled ‘A’, and B through F follow in a clockwise manner around the outside. The horizontal segment in the middle is labeled ‘G’.
Segment ‘Activation’
To make numbers on a typical digital clock, some of the segments are lit up. For example, for the number 1 the B and the C are lit up. A and D through G are not lit up, but can be seen in a darker, “grayed out” state.
Put another way, all of the numbers have seven segments. Some are active and some are inactive.
This activation can be a purely digital effect on modern screens but was traditionally formed by LED (or some other form of lighting) illuminating the active segments.
Physical interpretations of the 7-segment digital clock numbers font, such as through popsicle sticks, may eliminate the inactive segments altogether. Note, however, that this is rare in other implementations of digital clock numbers (including on modern screens) as the visibility of inactive elements greatly increases readability and assuredness that the correct time is being displayed.
Colon and Period
In some digital number fonts there is an eighth segment to the 7-segment design, a dot to the right of segment B’s bottom. It is labeled ‘DP’ for decimal point. You’ve probably seen it on old calculators if you looked closely or mashed your thumb on the screen hard enough to get the weird color effect.
Clocks don’t use the DP segment. There’s no need.
What clocks do need is a colon (this thing “:”) and, possibly, a marker to tell if it is in the AM or PM period of the day.
Fun Fact: The time between AM and PM is not the time between night and day.
These segments can be crafted separately. The colon’s two dots often blink and if they do so it is nearly always in unison. They are often in a secondary color. Meanwhile, the AM and PM indicators are almost always to the right of the numbers, in the upper right corner. The AM is displayed over the PM, with only the correct one being lit up, not blinking.
Segment Borders
In the supplied example above, each of the segments are made of non-touching rectangles.
However, it is very common to find digital clock fonts with irregularly shaped segments. These segments are able to touch (or come close to touching). This format increases readability.
This style of border is the kind most commonly found in alarm clocks.
Pros and Cons of 7-Segment Digital Clock Numbers
Like many things in life, the choice to use this digital clock number font is riddled with pros and cons. Here’s what to keep in mind about this digital clock number style.
Pros
- Simplicity: Seven-segment displays are straightforward in design and easy to understand. You don’t need too many numbers on the clock face for this style to work.
- Low Cost: Given their simplistic design, they are generally more affordable to produce than more complex displays.
- Versatility: They can be found in various electronic devices like digital clocks, calculators, microwaves, and gas station price signs.
- Durability: There are fewer components that can fail compared to more complex displays.
- Visibility: Their high contrast, especially with LED and OLED versions, makes them easily visible even from a distance.
- Energy Efficiency: Especially in designs that only light up the necessary segments, power consumption can be minimized.
- Historical Acceptance: Given their extensive usage over the years, people are accustomed to reading numbers from seven-segment displays.
- Ease of Programming: Due to its simplicity, it’s relatively easy to program microcontrollers or other electronic interfaces to work with seven-segment displays.
Cons:
- Limited to Numbers and Some Letters: Seven-segment displays can’t represent all alphanumeric characters comprehensively.
- Misinterpretation Risk: If a segment fails or isn’t visible due to external factors, numbers can easily be mistaken for others (e.g., a 9 might look like a 4).
- Aesthetics: Some might find their design less modern or sleek compared to full-screen digital displays.
- Scaling Issues: Making a large seven-segment display can be challenging since each segment’s size needs to increase, potentially leading to visibility issues or increased power consumption.
- Lack of Additional Information: The display only provides numbers and cannot give further context or data, like a full LCD might.
- Power Consumption Variability: Numbers with more segments lit (like 8) will consume more power than numbers with fewer segments lit (like 1).
Other Digital Clock Number Layouts
In reality, we are not limited to a strict 7-segment style display for digital number fonts. Larger segment numbers are able to properly display other characters, such as letters and symbols like the small, raised circle used for degrees.
Smaller segmented layouts are also possible but require a bit of creativity.
For 6, 5, and 4-segment digital clock prints, I highly recommend checking out the following YouTube video, which largely inspired me to make this post in the first place:
It gets weirder and weirder the smaller you go. Daring YouTubers are using rotation and unusual segment shapes to try to work in 3-segment style digital clock fonts and even 2-segment style ones. Do you think they work?
Conclusion
Ultimately, if you are a digital clock designer, there is a lot of creativity to be had with
