The **C4SMF-RJS** is a high-performance, oval-shaped **Red LED** manufactured by **Cree LED** (formerly Wolfspeed/Cree). It is specifically designed for outdoor electronic signs and signals. ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Color** | Red | | **Dominant Wavelength** | 621 nm (Typical) | | **Luminous Intensity** | 1100 - 4180 mcd (varies by bin) | | **Viewing Angle** | 70° (Horizontal) / 35° (Vertical) | | **Forward Current ($I_F$)** | 50 mA (Maximum) | | **Forward Voltage ($V_F$)** | 2.1 V (Typical) | | **Lens Shape** | 4mm Oval | | **Package Type** | Through-Hole (Radial) | --- ### 2. Core Electronic Characteristics #### A. Optical Design The C4SMF series uses an **Oval Lens** geometry. This is a critical electronic design choice for "Screen" applications. It creates a wide horizontal viewing angle ($70^\circ$) while maintaining a narrower vertical angle ($35^\circ$), ensuring that light is directed toward viewers on the street rather than being wasted pointing at the sky or the ground. #### B. Material Composition These LEDs are built using **AlGaInP (Aluminium Gallium Indium Phosphide)** technology. This material is preferred for red LEDs because it provides high luminous efficiency and excellent stability under varying temperature conditions. #### C. Reliability & Protection * **UV Resistance:** The epoxy lens contains UV inhibitors to prevent the plastic from yellowing or becoming brittle when exposed to direct sunlight for years. * **Moisture Resistance:** Designed for outdoor environments, though they still require proper PCB sealing (conformal coating) for long-term survival in rain. --- ### 3. Application Use Cases Because of its specific radiation pattern and high brightness, the C4SMF-RJS is primarily used in: 1. **Full-Color Video Signs:** Used as the red component in RGB pixel clusters for outdoor billboards. 2. **Variable Message Signs (VMS):** Highway traffic boards and speed limit signs. 3. **Petrol Station Price Signs:** Digital numerals for fuel pricing. 4. **Passenger Information:** Bus and train station arrival/departure boards. --- ### 4. Implementation Circuit (Example) To drive this LED at a standard 20mA using a 5V DC source, you would use a current-limiting resistor. ```python # Calculation Example V_source = 5.0 # Volts V_forward = 2.1 # Typical Volts for C4SMF-RJS I_target = 0.02 # 20mA (Standard Operating Current) # Ohm's Law: R = (V_source - V_forward) / I_target Resistance = (5.0 - 2.1) / 0.02 print(f"Required Resistor: {Resistance} Ohms") # Output: 145 Ohms ```