The **HJR-3FF-S-Z** (often referred to by its series HJR-3) is a popular, low-cost subminiature intermediate power relay. It is widely used in home appliances, office equipment, and industrial automation. --- ### 1. General Specifications The HJR series is a **Single Pole Double Throw (SPDT)** or **Single Pole Single Throw (SPST)** relay designed for PCB mounting. | Parameter | Specification (Typical) | | :--- | :--- | | **Contact Form** | 1 Form A (SPST-NO) or 1 Form C (SPDT) | | **Contact Rating** | 10A @ 120VAC / 7A @ 250VAC / 10A @ 24VDC | | **Coil Voltage (DC)** | 3V, 5V, 6V, 9V, 12V, 24V, 48V | | **Coil Power** | Approx. 0.36W (Standard) | | **Contact Resistance** | ≤ 100mΩ | | **Operating Time** | Max 10ms | | **Release Time** | Max 5ms | --- ### 2. Key Components & Construction The relay consists of several internal electronic and mechanical parts that allow it to function as a switch: * **Electromagnet (Coil):** A copper wire winding around an iron core. When energized, it creates a magnetic field. * **Armature:** A moving metal piece that is attracted to the electromagnet. * **Spring:** Returns the armature to its original position once power is removed from the coil. * **Contacts:** Usually made of silver alloy (AgSnO2 or AgCdO) to resist "pitting" and "welding" during high-current switching. * **Terminals:** PCB-type pins designed to be soldered directly onto a circuit board. --- ### 3. Pinout Configuration The standard 5-pin layout for the 1 Form C (SPDT) version is as follows: | Pin Name | Function | | :--- | :--- | | **Coil Pin 1 & 2** | Power input to energize the relay. | | **Common (COM)** | The terminal that moves between the other two. | | **Normally Closed (NC)** | Connected to COM when the relay is **OFF**. | | **Normally Open (NO)** | Connected to COM when the relay is **ON**. | --- ### 4. Implementation Example (Microcontroller) To drive an HJR relay using a 5V microcontroller (like an Arduino), you typically need a transistor to handle the coil current, as the GPIO pins cannot provide enough power. ```cpp // Simple Relay Control Logic int relayPin = 7; void setup() { pinMode(relayPin, OUTPUT); } void loop() { digitalWrite(relayPin, HIGH); // Relay ON (NO connects to COM) delay(2000); digitalWrite(relayPin, LOW); // Relay OFF (NC connects to COM) delay(2000); } ``` ---