The **C4SMK-RJS** is a high-performance, through-hole LED manufactured by **Cree LED** (now part of SMART Global Holdings). It belongs to the Screen Master® series, specifically designed for outdoor video screens and signage applications. --- ### ## Technical Specifications Overview The C4SMK-RJS is a **Red** LED utilizing AllnGaP (Aluminum Indium Gallium Phosphide) technology. It is a "High Brightness" oval LED. | Parameter | Specification | | :--- | :--- | | **Color** | Red (621 nm - 634 nm) | | **Lens Shape** | 4mm Oval | | **Luminous Intensity** | 550 - 2130 mcd | | **Viewing Angle** | 110° (Horizontal) / 50° (Vertical) | | **Forward Current** | 50 mA (Maximum) | | **Forward Voltage** | 2.1V (Typical) | | **Operating Temp** | -40°C to +100°C | --- ### ### Key Electronic Characteristics 1. **Optical Design (Oval Shape):** The "Oval" lens is a critical electronic design feature. It provides a wide horizontal viewing angle (110°) and a narrow vertical viewing angle (50°). This ensures that light is directed toward the viewers on the ground/street rather than being wasted pointing at the sky or the ground directly beneath the sign. 2. **Material Technology:** It uses **AllnGaP on a GaAs substrate**. This material provides high luminous efficiency and excellent reliability under high-temperature and high-humidity conditions, which is essential for outdoor environments. 3. **Binning Structure:** Cree LEDs are "binned" for consistency. For the C4SMK-RJS, this involves: * **Intensity Bins:** Sorted by millicandela (mcd) to ensure uniform brightness across a large display. * **Color Bins:** Sorted by dominant wavelength to ensure color uniformity. 4. **Standoff Options:** The part number often includes variations for "Standoffs" (little feet on the leads). These are used to keep the LED at a specific height from the PCB during the soldering process and to allow for easier cleaning. --- ### ### Typical Application Circuit When designing with the C4SMK-RJS, a current-limiting resistor is required to prevent thermal runaway. ```cpp // Basic Calculation for a 5V DC Supply: // R = (V_supply - V_forward) / I_forward // R = (5V - 2.1V) / 0.020A (Running at 20mA for longevity) // R = 145 Ohms (Use 150 Ohm standard resistor) ``` --- ### ### Common Use Cases * **Full-Color Video Screens:** Large stadium or billboard displays. * **Variable Message Signs (VMS):** Highway traffic alerts and transit signs. * **Amusement Lighting:** High-visibility park signage.