The **HFD3/24-L2-R-S-R** is a high-performance, subminiature signal relay manufactured by Hongfa. It is widely used in telecommunications, security systems, and medical equipment due to its high sensitivity and reliability. ### Part Number Breakdown Understanding the suffix codes is essential for identifying the specific technical characteristics of this component: | Code | Meaning | Description | | :--- | :--- | :--- | | **HFD3** | Series Name | Subminiature Signal Relay (4th Generation) | | **24** | Nominal Voltage | 24V DC Coil | | **L2** | Coil Type | **2-Coil Latching** (Bi-stable) | | **R** | Polarity | Standard Polarity | | **S** | Sealing | Plastic Sealed (Wash tight) | | **R** | Packaging | Reel Packaging (for SMT) | --- ### Key Technical Specifications #### 1. Coil Data (Control Side) Since this is a **2-coil latching** relay, it does not require continuous power to stay in an "On" or "Off" state. It uses one coil to "Set" the contact and a second coil to "Reset" it. * **Nominal Voltage:** 24 VDC * **Set/Reset Voltage:** ≤ 18 VDC (75% of nominal) * **Power Consumption:** Approx. 140mW * **Feature:** Energy efficient; the coil only needs a short pulse (typically >5ms) to switch states. #### 2. Contact Data (Switching Side) * **Contact Arrangement:** 2 Form C (DPDT - Double Pole Double Throw) * **Contact Material:** Silver Alloy + Gold Clad (Ag-Au) * **Max Switching Current:** 2A * **Max Switching Voltage:** 250VAC / 220VDC * **Max Switching Power:** 62.5VA / 60W #### 3. General Characteristics * **Mounting:** SMT (Surface Mount Technology) * **Insulation Resistance:** 1000MΩ (at 500VDC) * **Dielectric Strength:** 1500VAC (between coil and contacts) * **Life Expectancy:** 100,000,000 operations (Mechanical) --- ### Internal Wiring Diagram (Latching Type) Because it is a 2-coil latching relay, the pinout is more complex than a standard monostable relay. ```text [TOP VIEW] +-------------------+ | 10 9 8 7 6 | <-- Pins | o o o o o | | | | o o o o o | | 1 2 3 4 5 | +-------------------+ ``` * **Pins 1 & 10:** Coil 1 (Set) * **Pins 5 & 6:** Coil 2 (Reset) * **Middle Pins:** Common, Normally Closed (NC), and Normally Open (NO) contacts for the two poles. --- ### Typical Applications 1. **Telecommunications:** Switching signal paths in PABX or line cards. 2. **Battery Powered Devices:** Ideal because it consumes zero power once the state is switched. 3. **Test & Measurement:** High-speed signal switching with low thermoelectromotive force (EMF).