SRD-03VDC-SL-C SONGLE RELAY

SRD-03VDC-SL-C SONGLE RELAY – Subminiature 3V DC Power Relay

The SRD-03VDC-SL-C SONGLE RELAY (manufactured by Ningbo Songle Relay Co.) is a high-performance, compact 5-pin electromechanical power relay. Operating on a low 3 V DC nominal coil voltage, this subminiature relay features a 1 Form C (SPDT – Single Pole Double Throw) contact arrangement. Despite its small footprint, it can switch high-power electrical loads up to 10 A at 250 V AC or 30 V DC.

Deciphering the part code reveals its key attributes: SRD indicates the subminiature series, 03VDC specifies the 3 V DC coil power requirement, S denotes a sealed/washable protective structure, L represents high-sensitivity coil power consumption (0.36 W), and C signifies a Form C (SPDT) contact configuration.

As shown in the product image, the relay is housed in a distinct blue plastic case featuring standard PCB through-hole pins on the underside for easy soldering onto printed circuit boards.

Key Features of the SRD-03VDC-SL-C SONGLE RELAY

• High Switching Load (10 A Current Rating): Capable of directly controlling high-current AC/DC electrical loads up to 10 A.

• Low 3 V DC Drive Voltage: Optimized for low-voltage power sources, making it compatible with 3.3V microcontrollers (ESP32, STM32, Raspberry Pi Pico) and battery-operated circuits.

• Sensitive 0.36 W Power Consumption: The “L” type high-sensitivity coil requires minimal driving current (approx. 120 mA), reducing power loss across driver circuits.

• 1 Form C (SPDT) Contact Arrangement: Features standard Normally Open (NO), Normally Closed (NC), and Common (COM) pins for versatile switching operations.

• Sealed IP65 Construction: The fully encapsulated blue casing protects internal electrical contacts against dust ingress, flux contamination, and harsh ambient environments.

• Fast Operation Speed: Offers quick switching performance with a maximum operation time of le 10 ms and release time of le 5 ms.

Common Applications and Practical Usage

The high current handling and low driving voltage of the SRD-03VDC-SL-C SONGLE RELAY make it a preferred component in embedded electronics and low-voltage automation:

• Microcontroller Relay Boards: Acts as the primary switching element in 3.3V microcontroller expansion modules to trigger high-voltage lamps, pumps, and heaters.

• IoT & Home Automation Devices: Powers smart switches, smart plugs, and automated lighting modules controlled via Wi-Fi or Bluetooth chips.

• Battery-Powered Systems: Ideal for portable field equipment and solar-powered devices operating from 3.2V LiFePO4 or single-cell lithium-ion battery supplies.

• Automotive & Consumer Electronics: Used for signal isolation and load switching in automotive accessories and household appliances.

Technical Specifications

The core electrical, mechanical, and physical parameters for the SRD-03VDC-SL-C SONGLE RELAY are detailed below:

Operating Guidelines and Best Practices

CIRCUIT DESIGN TIP: Never drive the relay coil directly from a microcontroller I/O pin. Always use an NPN transistor (e.g., 2N2222) or MOSFET switch driver.

• Flyback Diode Protection: Connect a freewheeling diode (such as 1N4007) in reverse parallel across the relay coil terminals. This suppresses inductive back-EMF voltage spikes when turning off the coil, protecting drive transistors from destruction.

• PCB Trace Width: Keep high-voltage/high-current contact traces sufficiently wide (2.5 mm for 10 A) and isolated from sensitive low-voltage microcontrollers with adequate creepage distances.

To review official international IEC standards for miniature electromechanical elementary relays and safety testing protocols, consult the official IEC 61810-1 Electromechanical Elementary Relays Directory.

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