The **CB1-R-24V** is a high-power automotive relay manufactured by Panasonic (formerly Matsushita). It is specifically designed for 24V electrical systems, common in trucks, buses, and industrial machinery. --- ### 1. Key Technical Specifications Below are the primary electrical characteristics of the CB1-R-24V: | Feature | Specification | | :--- | :--- | | **Nominal Coil Voltage** | 24V DC | | **Contact Arrangement** | 1 Form C (SPDT - Single Pole Double Throw) | | **Contact Rating (Resistive)** | 20A at 28V DC | | **Max. Switching Current** | 20A (Normally Open) / 10A (Normally Closed) | | **Internal Feature** | **Resistor** built-in (Suppression) | | **Mounting Type** | Plug-in (ISO terminal layout) | --- ### 2. Electronic Components & Internal Design #### A. The Coil (Electromagnet) The coil is designed to operate at 24V DC. When current flows through it, it creates a magnetic field that moves the internal armature to switch the contacts. #### B. The "R" Suffix (Resistor Suppression) The "R" in the part number indicates that a **resistor** is wired in parallel with the coil. - **Purpose:** When a relay coil is turned off, the collapsing magnetic field creates a high-voltage spike (back-EMF). - **Benefit:** The resistor dissipates this spike, protecting sensitive control electronics (like a vehicle's ECU or a PLC) from electrical noise and damage. - **Comparison:** Unlike a diode (which is polar), a resistor-suppressed relay is **non-polar**, meaning you can connect positive/negative to either coil terminal (85/86). #### C. Contact Material The contacts are typically made of **Silver Alloy** (AgSnO₂). This material is chosen for its excellent resistance to "arc welding" and material transfer, which is common in high-current DC switching. --- ### 3. Terminal Configuration (ISO Standard) The relay follows the standard automotive terminal numbering: 1. **Terminal 85 & 86:** Coil connections (Power and Ground). 2. **Terminal 30:** Common (COM) - The input power source. 3. **Terminal 87:** Normally Open (NO) - Connected when the relay is active. 4. **Terminal 87a:** Normally Closed (NC) - Connected when the relay is at rest. --- ### 4. Common Applications Due to its 24V rating and high durability, it is frequently used for: * Heavy-duty vehicle lighting (Headlights, Fog lights). * Air conditioning blowers and cooling fans. * Power windows and motorized gates in 24V systems. * Fuel pump control in diesel engines.