STEM/Robotics/ATL Tinkering Curriculum | Level 1 | Experiment 6 | Print-1 on Seven -Segment Display
In this experiment, we will explore how to display numeric digits using a seven-segment display without the use of integrated circuits (ICs) or switches. A seven-segment display is a popular electronic component used to visually represent decimal numbers and some characters. By connecting the segments directly to a power source, we can illuminate specific segments to form numbers from 0 to 9. This experiment provides an opportunity to understand the functionality of seven-segment displays and the basic principles of circuit design, allowing learners to visualize how each segment contributes to displaying different numeric values.
Materials Required:
Seven-Segment Display (Common Anode or Common Cathode)
Resistors (220Ω for current limiting)
Breadboard
Connecting Wires
Battery (5V or 9V)
Circuit Diagram:
The seven-segment display is composed of 7 LEDs arranged in the shape of the number 8, with each segment named from ‘a’ to ‘g’. Depending on the type of display (Common Anode or Common Cathode), the wiring will differ slightly:
Common Cathode: Connect all the cathodes to the ground (GND) and control the segments by applying positive voltage (VCC) to each corresponding segment.
Common Anode: Connect all the anodes to the positive voltage (VCC) and control the segments by applying ground (GND) to each corresponding segment.
Power Connections:
Common Cathode Display:
Connect the common pin to GND.
Connect each segment (a-g) to VCC (positive terminal) of the battery through a 1kΩ resistor to limit the current.
Common Anode Display:
Connect the common pin to VCC.
Connect each segment (a-g) to GND through a 1Ω resistor to limit the current.
Steps to Construct:
Step 1: Place the seven-segment display on the breadboard.
Step 2: Identify the common pin of the display (for common anode, it’s connected to VCC; for common cathode, it’s connected to GND).
Step 3: For each segment (a-g), connect the corresponding pin of the seven-segment display to the battery using a 1kΩ resistor to limit the current.
Step 4: To display numbers, manually connect the wires from the battery terminals to the pins corresponding to the segments needed for each digit:
For 1: Light up segments b, c
Step 5: Test the circuit by connecting the wires manually to display different digits (0-9). Each digit will appear on the seven-segment display by lighting up the appropriate combination of segments.
Working Principle:
The seven-segment display works by illuminating specific segments of the display to form numbers. By connecting the power source directly to the appropriate segments, you can manually control which LEDs turn on and off, forming digits from 0 to 9. This manual method allows you to observe the operation of each individual segment.
For Common Cathode: The cathode (negative terminal) is shared, and each segment lights up when a positive voltage is applied to its corresponding pin.
For Common Anode: The anode (positive terminal) is shared, and each segment lights up when a negative voltage (GND) is applied to its corresponding pin.
Expected Outcome:
By manually connecting the wires to the appropriate pins, you can display any digit from 0 to 9 on the seven-segment display.
The segments will light up based on the wiring, forming the shape of the digit.
Safety Tips:
Use Current-Limiting Resistors: Always connect a 220Ω resistor in series with each segment to prevent excessive current, which could damage the LEDs in the display.
Correct Wiring: Ensure that the common pin is connected properly (either to VCC for common anode or GND for common cathode) to avoid malfunction.
Check Polarity: Double-check the polarity of the connections, especially when dealing with the common anode or cathode configuration.
Work in a Dry and Safe Environment: Ensure that the workspace is clean and dry to prevent any accidents.