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 $3text{ V DC}$ 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 $10text{ A}$ at $250text{ V AC}$ or $30text{ V DC}$ .

Deciphering the part code reveals its key attributes: SRD indicates the subminiature series, 03VDC specifies the $3text{ V DC}$ coil power requirement, S denotes a sealed/washable protective structure, L represents high-sensitivity coil power consumption ( $0.36text{ W}$ ), 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 ( $10text{ A}$ Current Rating): Capable of directly controlling high-current AC/DC electrical loads up to $10text{ A}$ .
Low $3text{ V DC}$ 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 $0.36text{ W}$ Power Consumption: The “L” type high-sensitivity coil requires minimal driving current (approx. $120text{ mA}$ ), 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 $le 10text{ ms}$ and release time of $le 5text{ ms}$ .

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 $3.2text{V}$ 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:

Parameter Specification	Technical Details & Operational Values
Component Classification	Subminiature Through-Hole Electromechanical Power Relay
Primary Target Keyword	SRD-03VDC-SL-C SONGLE RELAY
Manufacturer / Series	Ningbo Songle Relay Co. / SRD Series
Part Code Reference	`SRD-03VDC-SL-C`
Contact Form	1 Form C (SPDT: 1 NO, 1 NC, 1 COM)
Nominal Coil Voltage ( $U_n$ )	$3text{ V DC}$
Coil Resistance / Current	$25 Omega (pm 10%)$ / Approx. $120text{ mA}$
Coil Power Consumption	$0.36text{ W}$ (High-Sensitivity Type “L”)
Contact Capacity (Resistive)	$10text{ A}$ @ $250text{ V AC}$ / $10text{ A}$ @ $30text{ V DC}$
Max Switching Voltage	$250text{ V AC}$ / $110text{ V DC}$
Contact Material	Silver Alloy (AgCdO / AgNi)
Dielectric Strength	$1500text{ V AC}$ (1 min, between coil & contacts)
Electrical / Mechanical Life	$100,000text{ operations min.}$ / $10,000,000text{ operations min.}$
Dimensions ( $L times W times H$ )	$19.1text{ mm} times 15.5text{ mm} times 15.3text{ mm}$
Operating Ambient Temp	$-40^circtext{C to }+85^circtext{C}$

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 ( $>2.5text{ mm}$ for $10text{ A}$ ) 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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