How To Drive A 7-segment Display - The Learning Circuit

Summary

In this educational video, the host teaches viewers how to drive a seven-segment display using a BCD to seven-segment decoder. The tutorial covers the basics of seven-segment displays, including common anode and cathode configurations, and the use of a BCD decoder to translate binary to control LED segments. The practical demonstration involves connecting the decoder to switches for input and LEDs for indicator lights, with a focus on understanding the decoder's pin functions and wiring the circuit correctly. The video encourages learning about electronic components and invites viewers to share their projects on the element14 community.

Takeaways

• 😀 The video is about driving a seven-segment display using a BCD to seven-segment decoder.
• 🔢 Seven-segment displays are commonly used in technology to display numbers and consist of seven LED segments that can be lit up in various combinations.
• 🌐 The script mentions element14.com as a community for engineers to connect and collaborate.
• 🔌 There are two types of seven-segment displays: common anode, where all anodes are connected together, and common cathode, where all cathodes are connected.
• 🛠️ The LS447 is a seven-segment decoder used in the video to convert four-digit binary (BCD) into signals for the display segments.
• 📚 Understanding the decoder's logic can be achieved by reviewing the datasheet and logic diagram, which are complex and not detailed in the video.
• 🔩 The decoder chip has 16 pins with specific functions, including BCD inputs (A, B, C, D) and segment outputs (a-g).
• 🔑 The video demonstrates building a circuit with switches and LEDs to manually input BCD numbers and visualize them on the display.
• 💡 The display has an extra pin for the decimal point, which is also an LED and requires a current-limiting resistor.
• 🔌 Additional pins on the decoder, such as LT (Lamp Test), RBI (Ripple Blink Input), and BI (Blinking Input), have specific functions that are explained in the video.
• 🔄 The video concludes with a call to action for viewers to share projects involving multiplexers, demultiplexers, encoders, and decoders on the element14 community.

Q & A

What is the purpose of the element14 electronics community?

The element14 electronics community is a platform where top engineers from around the world can connect and collaborate.

What type of display is being discussed in the video?

The video discusses a seven-segment display.

Where might you have seen a seven-segment display before?

You may have seen a seven-segment display in alarm clocks, radios, or other pieces of technology that display numbers.

How are the segments of a seven-segment display controlled?

Each LED-lit segment of a seven-segment display is controlled by a separate pin.

What is the function of the extra pin labeled 'DP' on the seven-segment display?

The 'DP' pin controls the decimal point on the display.

What are the two types of seven-segment displays mentioned, and how are they different?

The two types of seven-segment displays are common anode and common cathode. In common anode displays, all the anodes are connected together, while in common cathode displays, all the cathodes are connected together.

What type of decoder is used in the video to drive the seven-segment display?

The video uses a BCD to seven-segment decoder, specifically the 74LS47 decoder.

What does BCD stand for, and what does it represent?

BCD stands for Binary Coded Decimal, which is a four-digit version of binary that represents decimal numbers.

How does the decoder translate BCD to control the seven-segment display?

The decoder translates four-digit binary input (BCD) into seven output signals that control the LED segments of the display.

How are the inputs and outputs of the 74LS47 decoder connected in the circuit?

The inputs (A, B, C, D) are connected to switches to manually input the BCD number. The outputs (a, b, c, d, e, f, g) are connected to the corresponding pins on the seven-segment display.

What additional components are used in the circuit to ensure proper operation of the LEDs?

Current limiting resistors are added to each LED segment to prevent excessive current and protect the LEDs.

What are the functions of pins 3, 4, and 5 on the 74LS47 decoder?

Pin 3 (LT) is for lamp test, pin 4 (BI/RBO) is for blanking input and ripple-blanking output, and pin 5 (RBI) is for ripple-blanking input.

How are the active low pins on the decoder handled in the circuit?

The active low pins (LT, BI/RBO, RBI) are connected to the supply voltage using a 1 kilo ohm resistor to keep them inactive.

What are the power supply connections for the seven-segment display and the 74LS47 decoder?

The common anode display's pins 3 and 8 are connected to the supply voltage, while the decoder's pin 16 is connected to the positive supply voltage and pin 8 to ground.

How can you test the functionality of the seven-segment display?

You can use the lamp test (LT) pin, which when pulled low, will turn on all segments of the display.

What might be a more common method to send input signals to the seven-segment display in practical applications?

In practical applications, a microcontroller is often used to send input signals instead of manual switches.

Where can viewers share their projects that incorporate the discussed ICs?

Viewers can share their projects on the element14 community at element14.com/thelearningcircuit.