Summary of Controlling 7-segments LED displays using AVR microcontroller
This article outlines methods to control 7-segment LED displays with microcontrollers, comparing non-multiplexed and multiplexed configurations. It details direct I/O connections, shift registers like the 74HC595 for efficient output expansion, and driver ICs such as the 74LS247 or MAX7219. The text highlights a specific circuit using two displays controlled by five I/O pins with low power consumption, alongside downloadable code files for implementation.
Parts used in Controlling 7-segments LED Displays:
- Microcontroller
- 7-segment LED display (TDSL-5160 Vishay)
- 74LS247 BCD-to-7-segments driver IC
- 74HC595 shift register
- NPN/PNP transistors
- MAX7219 special driver IC
1. One or two displays directly to the i/o’s
2. One display with a 74LS247
3. Two displays with a 74HC595 and two 74LS247
Multiplexed:
1. Two displays with a 74LS247 and 2 i/o’s
2. Two displays with a 74HC595 and 2 NPN/PNP *
3. With a special driver IC e.g. MAX7219
Controlling two displays:
There are several possibilities to connect a 7-segments LED display to a microcontroller.
Directly to the i/o’s of the microcontroller, or a more economic way, with a shift-register e.g. the 74HC595 and multiplex the displays. With a shift register you only need 3 i/o’s and you have 8 outputs. Another possibility is the 74LS247 a BCD -> 7-segments driver IC, this takes 4 i/o’s. The diagram shows two 7-segments LED displays controlled by only 5 i/o’s. Ofcourse you can add more displays. With a minimum of components you’re able to control a maximum of displays. The circuit consumes about 20 mA with TDSL-5160 (Vishay) 7-segments LED displays.
Download: upcounter.hex and upcounter.eep
For more detail: Controlling 7-segments LED displays using AVR microcontroller
- How can you connect displays directly to a microcontroller?
You can connect one or two displays directly to the i/o's of the microcontroller. - What is an economic way to control multiple displays?
A shift-register like the 74HC595 allows controlling displays with only 3 i/o's and 8 outputs. - Does the 74LS247 require many input/output pins?
Yes, the 74LS247 BCD-to-7-segments driver IC takes 4 i/o's. - Can you add more displays to the circuit described?
Yes, you can add more displays while maintaining a minimum of components. - What is the power consumption of the described circuit?
The circuit consumes about 20 mA when using TDSL-5160 Vishay 7-segments LED displays. - How many i/o's are needed to control two displays with a 74HC595?
With a 74HC595 and 2 NPN/PNP transistors, you can control two displays. - What component takes 4 i/o's according to the text?
The 74LS247 is the component that takes 4 i/o's. - Is it possible to use a special driver IC for this project?
Yes, you can use a special driver IC such as the MAX7219.
