The **3BC-R/Y** is a common classification for a **Bi-Color (Dual-Color) Light Emitting Diode (LED)**. In electronic component nomenclature, this specific part is designed to emit two different colors—Red and Yellow—from a single package. --- ### 1. Technical Specifications The "3BC" prefix typically refers to a **3mm Round (T-1)** package size with a **B**i-**C**olor configuration. | Parameter | Red (R) Specification | Yellow (Y) Specification | | :--- | :--- | :--- | | **Wavelength** | ~625 nm | ~590 nm | | **Forward Voltage ($V_f$)** | 1.8V - 2.2V | 2.0V - 2.4V | | **Max Forward Current ($I_f$)** | 20mA - 30mA | 20mA - 30mA | | **Luminous Intensity** | 10 - 50 mcd (Standard) | 10 - 40 mcd (Standard) | | **Viewing Angle** | 30° - 60° | 30° - 60° | --- ### 2. Physical Configuration There are two primary ways these LEDs are wired internally, which dictates how you use them in a circuit: #### A. Common Cathode (3-Pin) The Red and Yellow anodes have separate pins, but they share a middle negative (ground) pin. * **Pin 1:** Red Anode (+) * **Pin 2:** Common Cathode (-) * **Pin 3:** Yellow Anode (+) #### B. Bipolar / Bi-Directional (2-Pin) Two LED chips are connected in parallel but with opposing polarities (antiparallel). * **Current Flow A → B:** Lights up Red. * **Current Flow B → A:** Lights up Yellow. * **AC Current:** Creates a "blended" orange-ish color. --- ### 3. Circuit Integration Example When using a 3BC-R/Y LED with a 5V power supply, you must use a current-limiting resistor to prevent the LED from burning out. ```python # Formula: R = (V_supply - V_forward) / I_forward # For Red LED: # R = (5V - 2.0V) / 0.02A = 150 Ohms # For Yellow LED: # R = (5V - 2.1V) / 0.02A = 145 Ohms (Use 150 standard) ``` --- ### 4. Typical Applications * **Status Indicators:** Red for "Error/Stop," Yellow for "Standby/Warning." * **Battery Charging:** Red for "Charging," Yellow/Amber for "Low Battery." * **Network Equipment:** Indicating different data speeds or link statuses on routers.