A 7-segment display is a device that can show numbers and some letters by lighting up different combinations of segments.
Each segment is a light-emitting diode (LED) or a liquid crystal display (LCD) that can be turned on or off by applying a voltage. A 7-segment display has eight segments, including a decimal point (DP), arranged in the shape of an “8”.
A 7-segment display can be used to display decimal digits from 0 to 9, and some hexadecimal digits from A to F. To display a digit, the corresponding segments must be turned on while the others are turned off. For example, to display the digit 0, the segments A, B, C, D, E, and F must be turned on, while the segments G and DP must be turned off. The table below shows the segment combinations for each digit:
| Digit | Segments |
|---|---|
| 0 | ABCDEF |
| 1 | BC |
| 2 | ABDEG |
| 3 | ABCDG |
| 4 | BCFG |
| 5 | ACDFG |
| 6 | ACDEFG |
| 7 | ABC |
| 8 | ABCDEFG |
| 9 | ABCDFG |
| A | ABCEFG |
| B | CDEFG |
| C | ADE |
| D | BCDEG |
| E | ADEFG |
| F | AEFG |
To control a 7-segment display, we need a circuit that can provide the right voltage to each segment.
One way to do this is to use a special integrated circuit (IC) called a 7-segment decoder/driver, such as the CMOS 4511. This IC can take a binary-coded decimal (BCD) input and convert it to the appropriate segment output. A BCD input is a four-bit binary number that represents a decimal digit from 0 to 9. For example, the BCD input for the digit 5 is 0101.
The CMOS 4511 has four BCD inputs labeled A, B, C, and D and seven-segment outputs labeled a, b, c, d, e, f, and g.
It also has three control inputs: lamp test (LT), blanking (BI), and latch enable (LE). The lamp test input can be used to turn on all the segments at once for testing purposes. The blanking input can be used to turn off all the segments regardless of the BCD input. The latch enables input can be used to store the BCD input in internal memory and display it until a new input is given.
The CMOS 4511 can work with either common-cathode or common-anode 7-segment displays. A common-cathode display has all the cathodes (negative terminals) of the LEDs connected together, while a common-anode display has all the anodes (positive terminals) of the LEDs connected together. The common terminal is then connected to either ground or power supply, depending on the type of display.
The CMOS 4511 has an active-low logic for its inputs and outputs, which means that a low voltage (0 V) represents logic 1 and a high voltage (Vcc) represents logic 0. Therefore, to turn on a segment, we need to apply a low voltage to its output pin and a high voltage to its common terminal.
In this article, we will show you how to build a simple circuit using a CMOS 4511 IC and a common-cathode 7-segment display. We will also explain how to use an eight-position DIP switch to provide the BCD input and how to use resistors to limit the current through the LEDs.
What You Need
To build this circuit, you will need the following components:
- A CMOS 4511 IC
- A common-cathode 7-segment LED display
- An eight-position DIP switch
- Four 10 kΩ resistors
- Seven 470 Ω resistors
- A breadboard
- Some jumper wires
- A power supply of about 6 V
How to Connect the Components
To connect the components on the breadboard, follow these steps:
- Insert the CMOS 4511 IC on the breadboard so that its pins are across the center gap.
- Connect pin 16 of the IC (Vcc) to the positive rail of the breadboard and pin 8 of the IC (GND) to the negative rail of the breadboard.
- Connect pins A, B, C, and D of the IC (pins 7, 1, 2, and 6) to one side of four resistors of value 10 kΩ each. Connect the other side of these resistors to four adjacent pins of one side of the DIP switch.
- Connect pin LT of the IC (pin 3) to Vcc through another resistor of value 10 kΩ. This will keep all the segments off during normal operation.
- Connect pin BI of the IC (pin 4) to GND. This will enable the normal operation of the segments according to the BCD input.
- Connect pin LE of the IC (pin 5) to GND. This will allow the immediate display of any change in BCD input.
- Connect pins a, b, c, d, e, f, and g of the IC (pins 15, 14, 13, 12, 11, 10, and
to one side of seven resistors of value 470 Ω each. Connect the other side of these resistors to the corresponding pins of the 7-segment display. Make sure to match the segment labels. 8. Connect the pin DP of both IC and display together if you want to use it as an additional segment. 9. Connect one common pin of both IC and display together and then connect it to Vcc through another resistor of value 470 Ω. This will provide a power supply for all segments. 10. Connect one common pin of both sides of the DIP switch together and then connect it to GND. This will provide ground for all switches.
How to Use It
Once you have connected all components, as shown above, you can turn on your power supply and start using your circuit. To display any digit from 0 to 9 on your 7-segment display, you need to set your DIP switch according to its BCD code.
For example, to display 5, you need to set your DIP switch as 0101 from left to right. This means that you need to turn on switches A and C and turn off switches B and D . You can use Table 1 as a reference for other digits. You can also try displaying some hexadecimal digits from A to F by setting your DIP switch accordingly.
Conclusion
In this article, you learned how to build a simple circuit using a CMOS 4511 IC and a common-cathode 7-segment display. You also learned how to use an eight-position DIP switch to provide BCD input and how to use resistors to limit current through LEDs.You gained familiarity with active-low logic inputs and outputs and how they work with common-cathode displays. You also learned how BCD code is used to represent decimal digits, and how it is decoded by CMOS 4511 IC.
This circuit can be used as a basic building block for more complex projects involving multiple displays, numbers greater than ten, and decimal points. You can also experiment with different types of displays, such as LCDs or common-anode LEDs, and different types of decoder/driver ICs, such as CMOS 4543. You can also try adding some buttons or sensors instead of switches to make your circuit more interactive.
We hope you enjoyed this article and learned something new. If you have any questions or comments about this project or any suggestions for future projects, you can leave them in our comment section below. Thank you for reading!
