### Electronic Specifications: CB1AF-R-24V The **CB1AF-R-24V** is a high-power automotive relay manufactured by Panasonic (formerly Matsushita). It is designed for heavy-duty applications within 24V vehicle systems, such as trucks, buses, and construction equipment. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Contact Form** | 1 Form A (SPST - Normally Open) | | **Nominal Coil Voltage** | 24V DC | | **Contact Rating (Resistive)** | 20A at 28V DC | | **Protective Feature** | Built-in Resistor (R) | | **Mounting Type** | Plug-in / ISO Type | | **Enclosure** | Flux-resistant (IP40 equivalent) | --- ### 2. Breakdown of the Component Parts #### A. The Built-in Resistor ("-R") The "R" in the part number signifies an internal **surge-suppression resistor** connected in parallel with the coil. - **Function:** When the relay coil is de-energized, the magnetic field collapses, creating a high-voltage spike (back-EMF). - **Benefit:** The resistor dissipates this energy, protecting sensitive electronic control units (ECUs) and switching transistors from voltage damage. #### B. Contact Material and Mechanism - **Material:** Typically Silver Alloy (AgSnO₂), which is resistant to contact welding and material transfer during high-current switching. - **Form A:** This is a "Normally Open" contact. The circuit is only completed when the 24V coil is energized. #### C. Coil Characteristics - **Pick-up Voltage:** The minimum voltage required to close the contacts (typically ~14V DC for this 24V model). - **Drop-out Voltage:** The voltage level at which the contacts will release (typically ~2.4V DC). - **Power Consumption:** Optimized for automotive environments to prevent excessive battery drain while maintaining high holding force. --- ### 3. Application Use Cases This specific relay is commonly found in the following systems: 1. **Engine Cooling Fans:** High-current switching for thermal management. 2. **Lighting Systems:** Controlling heavy-duty headlights or work lamps. 3. **Fuel Pumps:** Providing reliable power to fuel delivery systems. 4. **Heating Systems:** Managing high-draw defrosting elements in large vehicles. --- ### 4. Terminal Pin Layout (ISO Standard) Standard ISO 7588-1 terminal numbering: - **Pins 85 & 86:** Coil terminals (Input). - **Pins 30 & 87:** Switch terminals (Load).