The term **FND-R** typically refers to a **Flexible Numeric Display (FND)** with a **Red** LED output. In electronic components, an FND is more commonly known as a **7-Segment Display**. These are used to display decimal numerals and are common in digital clocks, meters, and home appliances. --- ## 1. Internal Structure and Circuitry An FND consists of 7 individual LEDs (segments) arranged in a figure-eight pattern, plus an optional 8th LED for the decimal point (DP). ### Segment Mapping Each segment is assigned a letter from **a** to **g**: * **a, b, c, d, e, f, g**: The main segments forming the number. * **DP**: Decimal Point. ### Connection Types FNDs come in two primary electrical configurations: | Type | Description | Connection Logic | | :--- | :--- | :--- | | **Common Cathode (CC)** | All negative terminals of the LEDs are tied together. | Connect Common to GND; apply HIGH voltage to segment pins to light them. | | **Common Anode (CA)** | All positive terminals of the LEDs are tied together. | Connect Common to VCC; apply LOW voltage to segment pins to light them. | --- ## 2. Technical Specifications (Typical for Red FND) The "R" in FND-R denotes the color Red. Red LEDs have specific electrical characteristics compared to Blue or Green ones. | Parameter | Typical Value | | :--- | :--- | | **Forward Voltage ($V_f$)** | 1.8V to 2.2V | | **Forward Current ($I_f$)** | 10mA to 20mA per segment | | **Peak Wavelength** | 630nm - 660nm | | **Power Dissipation** | 30mW - 60mW per segment | --- ## 3. How to Drive an FND-R To prevent the LEDs from burning out, you must use **current-limiting resistors**. ### Calculation Example If using a 5V microcontroller (like Arduino): $$R = \frac{V_{source} - V_f}{I_f} = \frac{5V - 2V}{0.02A} = 150 \Omega$$ ### Basic Wiring Code (Arduino Example) ```cpp // Example: Lighting up the number '1' (segments b and c) // for a Common Cathode FND void setup() { pinMode(2, OUTPUT); // Segment b pinMode(3, OUTPUT); // Segment c } void loop() { digitalWrite(2, HIGH); digitalWrite(3, HIGH); } ``` --- ## 4. Common Part Numbers If you are looking for specific FND-R components, they often follow these naming conventions: * **507-R**: 0.5-inch Red FND. * **LD-501xR**: Single digit Red. * **FND500 / FND507**: Standard industrial codes for red 7-segment displays.