I’ll show you how I made a basic 3′′ seven-segment display out of 5mm LEDs. This project was completed during the research and development phase of the Scoreduino project.
This COMMON CATHODE seven-segment display is made up of 29 pieces of 5mm LEDs. There is also a driver for this display. This is an excellent exercise for students interested in understanding how a seven-segment display and its driver work. CD4026 is used in the display driver, which has previously been used in our up counter modules.
The driver is little more than a counting machine. After plugging the display into the driver’s headers and turning it on, just press the COUNT switch to increase the count.
It works in the same way as other seven-segment displays. A CD4026b-based driver was also produced. The seven-segment display may be tested immediately away because it fits into the driver’s headers. The driver is a simple counter that simply counts up. To put the display to the test, just switch it on.
Schematic of common cathode seven segments display:
Schematic of the common cathode seven-segment display driver
The driver and seven-segment displays are theoretically similar to our CD4026 based up counter or common cathode driver.
Components required to build this seven-segment display
- 29 x LEDs.
- 2 x 5 pin header
- 2 x 5 pins male headers
Components required to build the driver for the seven segments display:
- 1 x PCB
- 2 x 5 pins female headers
- 2 x 2 pins headers
- 2 x tactile switches
- 1 x 3mm LED
- 1 x Screw terminal
- 1 x 16 pin IC socket
- 1 x CD4026 up counter chip
- 3 x 10K resistors
- 1 x 1K resistors
- 1 x PC817 optocoupler
- 1 x 101J resistor network array
- 7 x BC547 NPN transistors
- 2 x 4 pins angle header (this is optional, you would need this if you want to concatenate other drivers)
You will need a 9V power supply to operate the driver.