An LED (Light Emitting Diode) labeled with "35" typically refers to the physical dimensions of the component in the SMD (Surface Mount Device) format, specifically the **SMD 3528**. --- ## 1. Physical Specifications The "35" stands for **3.5mm**, representing the length of the LED chip. | Feature | Specification | | :--- | :--- | | **Dimensions** | 3.5mm x 2.8mm | | **Shape** | Rectangular | | **Form Factor** | SMD (Surface Mount Device) | | **Typical Height** | 1.9mm | --- ## 2. Electronic Characteristics The SMD 3528 is a single-die LED, meaning it contains one light-emitting crystal. It is considered a low-power LED. ### Electrical Parameters * **Forward Voltage ($V_f$):** Usually **2.0V - 2.2V** for Red/Yellow and **3.0V - 3.4V** for Blue/White. * **Forward Current ($I_f$):** Standard operating current is **20mA**. * **Power Consumption:** Approximately **0.06 Watts**. * **Luminous Intensity:** Generally ranges from **6 to 8 Lumens**. --- ## 3. Internal Components An LED 3528 consists of several key electronic parts: 1. **Semiconductor Die:** The "heart" of the LED (Gallium Nitride for Blue/White, AlGaInP for Red). 2. **Lead Frame:** The metal structure that provides electrical connections and acts as a heat sink. 3. **Gold Wire Bond:** A microscopic wire connecting the die to the electrodes. 4. **Encapsulant:** An epoxy or silicone resin that protects the die and helps diffuse light. 5. **Phosphor Layer:** Only found in white LEDs; converts blue light into a broad white spectrum. --- ## 4. Comparison Table: 3528 vs. 5050 | Feature | SMD 3528 | SMD 5050 | | :--- | :--- | :--- | | **Size** | 3.5mm x 2.8mm | 5.0mm x 5.0mm | | **Power** | 0.06W (Low) | 0.24W (High) | | **Brightness** | ~7 Lumens | ~20 Lumens | | **Best Use** | Accent lighting, backlighting | Task lighting, RGB color changing | --- ## 5. Circuit Implementation When using an LED 3528, a current-limiting resistor is required to prevent burnout. ```python # Formula to calculate Resistor (R) # R = (Source_Voltage - Forward_Voltage) / Forward_Current source_v = 12.0 forward_v = 3.2 # For White LED forward_i = 0.02 # 20mA resistor_needed = (source_v - forward_v) / forward_i print(f"Required Resistor: {resistor_needed} Ohms") ```