The **HJR-66-R** is a specific model of a **Miniature Intermediate Power Relay**, widely used in industrial automation, security systems, and telecommunication devices. It is manufactured primarily by companies like **Tianbo** and **HKE**. --- ### 1. Key Technical Specifications The following table highlights the critical electrical and physical parameters of the HJR-66-R: | Parameter | Specification (Typical) | | :--- | :--- | | **Contact Arrangement** | 1 Form A (SPST-NO) or 1 Form C (SPDT) | | **Contact Rating** | 5A to 12A @ 250VAC / 30VDC | | **Coil Voltage (DC)** | 3V, 5V, 6V, 9V, 12V, 24V, 48V | | **Coil Power** | Approx. 0.36W to 0.45W | | **Contact Resistance** | ≤ 100mΩ | | **Dielectric Strength** | 1,000VAC (between open contacts) | | **Mechanical Life** | 10,000,000 operations | --- ### 2. Internal Components & Construction The HJR-66-R consists of several internal electronic and mechanical parts: * **Electromagnetic Coil:** A copper wire winding around an iron core. When current flows, it creates a magnetic field to move the armature. * **Armature:** The moving metal part that responds to the magnetic field. * **Spring Mechanism:** Returns the armature to its original position when the coil is de-energized. * **Contacts (Silver Alloy):** Usually made of **AgCdO** (Silver Cadmium Oxide) or **AgSnO2** (Silver Tin Oxide) to provide high conductivity and resistance to "pitting" or welding during high-current switching. * **Terminals:** PCB-mount pins designed for soldering directly onto circuit boards. --- ### 3. Part Number Decoding (HJR-66-R-12VDC) To understand a specific unit, you must decode the suffix: 1. **HJR-66:** Basic series designation. 2. **R:** Indicates the relay is "Sealed Type" (Wash tight), meaning it can withstand PCB cleaning processes. 3. **12VDC:** The required voltage to activate the coil. 4. **S / Z:** Often denotes the contact form (S = 1 Form A; Z = 1 Form C). --- ### 4. Circuit Implementation When using the HJR-66-R in a digital circuit (like with an Arduino or ESP32), you should always include a **Flyback Diode** to protect your electronics. ```cpp // Example: Driving the HJR-66-R Coil via a Transistor [VCC 12V] --- [Relay Coil] --- [Collector of NPN Transistor] | [Flyback Diode (1N4007)] | [GND] -------- [Emitter of NPN Transistor] ``` ---