SRD-05VDC-SL-C Songle Relay SRD-05VDC-SL-C Power Relay – High-Current SPDT Control

Songle Relay SRD-05VDC-SL-C Power Relay Overview: Features, Specs, and Uses

The Songle Relay SRD-05VDC-SL-C is a widely adopted, PCB-mount power relay designed for general-purpose load switching in consumer electronics, white goods, HVAC controllers, lighting modules, UPS/SMPS auxiliary circuits, and industrial control boards. With a 5 VDC non-polarized single-coil and SPDT (1 Form C, changeover) contacts, it provides flexible routing of common (COM) to normally-open (NO) or normally-closed (NC) paths. Its compact, through-hole package (about 19.2 × 15.6 × 15.8 mm) makes it easy to drop into dense controller PCBs while still delivering up to 15 A current handling at 250 VAC (model-dependent), robust dielectric strength, and a sealed housing for process-friendly assembly and field reliability.

Songle’s SRD series is known for quick operate/release times (≈10 ms/10 ms), stable contact resistance, and long electrical and mechanical life for cost-effective, high-volume designs. The SRD-05VDC-SL-C variant specifically targets low-voltage logic control (5 V drive) while switching mains-level AC or high-current DC loads on the power side. Its 360 mW coil keeps control-side power draw modest, which is especially beneficial in battery-backed or thermally constrained enclosures. The relay carries common safety approvals and meets practical environmental limits, including –40 °C to +85 °C / +105 °C ambient capability across the series, making it suitable for products deployed in challenging climates. (Key ratings and drawings are summarized from the SRD series datasheet; see page 1 for ratings and page 2 for the footprint and pinout illustrations.)

Specifications

The following table consolidates typical values for SRD-05VDC-SL-C and relevant SRD series data. For design sign-off, always verify the exact sub-rating you source. Dimensions, ratings, and tolerances are summarized from the SRD datasheet: page 1 (ratings) and page 2 (footprint/pinout and certifications).

(All specification bullets summarized from the SRD series technical sheet, incl. coil table and timing/insulation data on page 1, and footprints and certification marks on page 2.)

Design & integration guidance

Driving the coil (5 V logic):
The SRD-05VDC-SL-C’s ≈ 70 Ω coil draws roughly 71 mA at 5 V (I≈V/R), so most microcontrollers can’t drive it directly from a GPIO. Use a low-side NPN/MOSFET driver (or a relay driver IC) with a flyback diode across the coil to suppress voltage spikes. For PWM or rapid on/off control, observe the relay’s mechanical limits and avoid chatter that could shorten contact life.

Contact protection:
Switching inductive loads (motors, solenoids, transformers) generates high dv/dt/di/dt and arcing. To maximize life and maintain low contact resistance:

• Add RC snubbers across AC loads, or TVS diodes/flyback paths for DC loads.

• Choose contact material and rating appropriate to your load type (resistive vs inductive).

• Derate current at elevated ambient temperatures and consider duty cycle.

Thermal considerations:
At higher currents, self-heating and trace/Pad I²R losses matter. Use wide copper pours, adequate spacing, and, if needed, heatsinking via copper planes. Ensure enclosure airflow accommodates the relay’s thermal rise.

PCB footprint & pinout:
The SRD package uses 5 pins: two coil pins and three contact pins (COM, NO, NC). Datasheet page 2 shows the bottom view PCB pattern and pin schematic for the changeover “C” type, along with diagrams for NO (“A”) and NC (“B”) variants. Verify your land pattern, hole diameters, and keep-out regions against the manufacturer’s drawing before committing to tooling.

Cleaning & environment:
The sealed housing helps prevent flux ingress and supports post-solder board washing. For high-humidity or dusty deployments, the sealing and ≥ 100 MΩ insulation performance contribute to long-term stability. If the application is exposed to >85 °C ambient, consult derating and consider models within the +105 °C capable subset of the series.

Compliance & safety:
The series shows cURus, CQC, and other approval marks on the datasheet. When designing for regulated markets, reference the manufacturer’s latest certificates and ensure creepage/clearance, trace spacing, and protective earth design match your system category and mains environment. Dielectric strength values (1500 VAC coil-to-contacts; 1000 VAC open contacts) are meaningful but do not replace full product-level safety testing.

Applications

• Home appliances: Compressors and fan motors in refrigerators/air conditioners; heater elements in ovens, kettles, and dryers; water-pump actuators in dishwashers and washing machines.

• Lighting & building control: Switched mains lighting, contactor pilot, blind/shade motors, and power distribution modules.

• Power & energy: Auxiliary switching in UPS/PSU designs, battery chargers, inverters (low-voltage control side), and energy meters requiring isolation between logic and mains.

• HVAC & environmental systems: Thermostat outputs, zone valves, humidifier/dehumidifier switching, and air-quality controllers.

• Industrial/IoT controllers: PLC I/O cards, relay hats/shields for microcontroller and SBC projects (Arduino/Raspberry Pi with driver), vending and access systems, and general automation.

• Safety/fail-safe routing: SPDT topology supports fail-safe paths—for example, energize-to-run (NO) or de-energize-to-safe (NC) strategies in control logic.

Engineering tips & best practices

1. Select the right contact form and rating:
   The “C” changeover contact covers the widest use cases. For strictly make-only circuits, an “A” (NO) contact may offer a slightly different rating. Always match the 7A/10A/15A series capability to your exact load profile and local standards.

2. Mind inrush & inductive kick:
   Incandescent lamps, SMPS inputs, and motor starts can exceed steady-state currents by 5–10× for milliseconds. Use inrush limiters (NTC, resistors), soft-start, or snubbers to protect both the relay and the downstream device.

3. Drive headroom & brownout:
   Keep coil voltage within bounds: ensure ≥ pickup under worst-case supply/temperature, and don’t exceed overload for sustained periods. Incorporate flyback and consider freewheel clamps that don’t slow release time excessively if fast drop-out is needed.

4. Layout & spacing:
   Respect creepage/clearance between coil and contact copper regions, and segregate high-voltage nets from the logic side. Follow the bottom-view footprint and drill sizes shown on the datasheet to avoid mis-wiring COM/NO/NC. (See page 2 diagram.)

5. Lifecycle planning:
   Mechanical relays are consumables. Validate your switching frequency (e.g., ≤ 1.8 k cycles/hour per datasheet life test notes) and build wear-out margins into maintenance plans. If your application cycles rapidly, consider SSRs or a hybrid approach to reduce arcing during frequent transitions.

Why choose SRD-05VDC-SL-C for your design?

• Proven, global ecosystem: The SRD series appears in countless reference designs, shields/hats, and open-source projects—making prototyping straightforward and spares easy to source.

• Balanced performance & cost: You get 15 A-class switching in a small, affordable package with 5 V coil compatibility and widely available sockets/headers for production.

• Assembly-friendly: Through-hole form factor simplifies manual or wave-solder assembly, while the sealed body tolerates post-solder cleaning.

Quick selection checklist

• Coil control rail is 5 V and can supply ≈ 70–75 mA per relay (or use a transistor driver).

• Load profile (resistive vs inductive) and inrush are understood and mitigated.

• Board layout respects footprint, creepage/clearance, and thermal limits.

• Regulatory pathway aligns with the series’ shown approvals; final product certified to end-standard.

• Sealed housing is preferred for environmental robustness and cleaning.

Notes on ordering & variants

Songle’s ordering string (e.g., SRD-12VDC-SL-C shown in the datasheet) indicates rated coil voltage, sealing, and contact form. For SRD-05VDC-SL-C, the key is 5 V coil, sealed body, SPDT changeover (“C”). The series provides multiple contact materials (AgCdO / AgSnO₂ / AgNi) and load classes (7 A/10 A/15 A) so distributors may list slightly different sub-ratings; always match the exact sub-type to your application and compliance needs. See page 1 of the datasheet for the coil table and ratings, and page 2 for footprint and pin diagrams.

Typical schematic snippet (textual)

• Control side (5 V): MCU GPIO → Gate/Base of MOSFET/NPN → Relay coil to +5 V; flyback diode across coil (cathode to +5 V).

• Power side: Line/Load routed through COM with NO for energized-to-on or NC for fail-safe off. Add RC/TVS across the load if inductive.

Applications in detail

Home appliances & white goods
Start/stop compressors, pumps, fan motors, and heating elements. The SPDT contact enables safety interlocks (e.g., door/over-temp switches). A sealed case helps with moisture and detergent vapors encountered during appliance cycles.

Lighting & building automation
Switch LED drivers, incandescent/halogen fixtures, and ballasts. Use snubbers for capacitive/inductive input supplies. SPDT allows manual override or power-fail modes.

Power systems & chargers
Isolate AC mains from control logic in UPS, PDU, and battery charger designs. The 1500 VAC coil-to-contact dielectric offers robust isolation at the board level (still verify system creepage/clearance to your end standard).

HVAC & environment
Thermostat outputs, zone valves, humidifier relays, and fan speed relays. The quick actuation improves response to PID or on/off temperature control algorithms without introducing undue lag.

Industrial & maker platforms
From PLC I/O cards to Arduino/Raspberry Pi relay shields (with driver), the SRD’s ubiquity makes it perfect for prototypes that later scale to production with the same footprint and BOM class.

Purchasing summary

• Part: SRD-05VDC-SL-C (5 V coil, SPDT “C”, sealed)

• Ratings: Up to 15 A @ 250 VAC (series), dielectric 1500 VAC / 1000 VAC, ≤ 10 ms operate/release

• Coil: ≈ 70 Ω, ≈ 71 mA, ≈ 360 mW at 5 V

• Body: Through-hole, sealed, compact 19.2×15.6×15.8 mm outline

• Use cases: Appliances, HVAC, lighting, power/UPS, automation I/O

For critical loads or safety circuits, validate with end-application testing (inrush, ambient, cycling rate, pollution degree), and confirm the exact contact material and sub-rating with your distributor before release to manufacturing.