Seven-segment display is an electronic display device used to display decimal numbers. It is an alternative to more complex dot matrix displays and is widely used in digital clocks, electronic meters, basic calculators, and other electronic devices that display digital information.
I. Basic Structure
1. Segments
- Seven-segment displays consist of seven individual segments, usually labeled a, b, c, d, e, f, and g. These segments are the light-emitting or displaying parts. For example, in a common cathode digital tube, to display the number 8, a, b, c, d, e, f, and g need to be high, so that these segments will light up and combine into the shape of the number 8; and to display the number 1, b and c are high, and a, d, e, f, and g are low, so that the shape of the number 1 is displayed.
2. Digit Select Pins
- In addition to the segment select pins, there are also bit select pins for the combination of multiple digital tubes. For example, four digital tubes may have four bit select pins (such as D1, D2, D3, and D4). The bit select pin determines which digital tube is displayed. When the bit select pin is high (in the case of common cathode), the corresponding digital tube lights up, and when it is low, the digital tube turns off.
2. Display principle
1. Single digit display
- Each digit has its own specific segment combination for display. Taking the common cathode seven-segment display as an example, the display of the number 0 requires the a, b, c, d, e, and f segments to be high (g is low), because according to the layout of its segments, such a level setting can make these segments light up and combine into the shape of the number 0. Similarly, the display of the number 2 requires a, b, d, e, and g to be high, and c and f to be low.
2. Multi-digit digital display
- When multiple digits need to be displayed, it is achieved through the coordination of the bit select pin and the segment select pin. For example, to display a two-digit number "12", first select the left digital tube (corresponding to the tens digit) through the bit select pin, and then set the segment select pin to display the level combination of the number 1 (that is, b and c are high, a, d, e, f, and g are low); then select the right digital tube (corresponding to the ones digit) through the bit select pin, and set the segment select pin to display the level combination of the number 2 (a, b, d, e, g are high, c, f are low).
3. Digital change display
- In some applications, such as counters. Take a hexadecimal counter as an example, if you want to display an increasing hexadecimal number on a seven-segment display. At the beginning, an initial configuration of eight digits m is displayed, and this number increases by 1 every second (assuming it is updated once per second). When the number increases to greater than the hexadecimal number "FFFFFFFF", the counter will set the number to 0 and continue to display. When displaying each number, the seven-segment display sets the corresponding segment to the correct level state according to the number to be displayed, and continues this display process according to the total working time n seconds. At the same time, each time a number is displayed, a certain amount of energy is consumed. Different numbers consume different amounts of energy. For example, displaying the number 0 consumes 6 units of energy per second, displaying the number 1 consumes 2 units of energy per second, and so on. The total energy consumption is the sum of the energy consumed when displaying each number.
