SSR-40DA Solid State Relay — Wear-free, silent, spark-free AC switching
Electromechanical relays eventually wear out. They are noisy and prone to sparking. If you are frequently switching AC loads—such as heating elements, motors, or industrial lighting—you need a more reliable solution. The SSR-40DA Solid State Relay handles up to 40A at 380V AC using a simple 3–32V DC control signal, with no moving parts whatsoever.
Note: The SSR-40DA is designed exclusively for switching alternating current (AC) loads. For DC loads, please use the SSR-DD model.
Why choose this model? (Key Advantages):
- Zero mechanical wear — With no physical contacts, the lifespan far exceeds that of traditional electromechanical relays in high-frequency switching applications.
- Directly compatible with Arduino, Raspberry Pi, and PLC — Accepts control signals from 3V DC, including the 3.3V pins on a Raspberry Pi, without the need for extra resistors.
- 2500V AC optical isolation — Your control circuit remains completely galvanically isolated from the mains voltage, ensuring safety regardless of load conditions.
- Sub-10ms switching time — Provides rapid response for time-sensitive applications, such as PWM temperature control or industrial automation.
- Integrated LED indicator — Instantly verify the relay status at a glance without needing a multimeter.
- Wide operating temperature — Stable performance from -30°C to +75°C, making it ideal for electrical cabinets, technical rooms, or industrial environments with thermal fluctuations.
Performance and Specifications
The TRIAC output ensures smooth switching across both half-cycles of the AC voltage, providing precise control for both resistive loads (heaters, lamps) and inductive loads (motors, transformers). The internal optical isolation creates a robust galvanic barrier between your 3–32V DC signal and the high-voltage circuit, protecting your microcontrollers from feedback. The compact 6.5 × 5 × 2.5 cm housing mounts easily to a heatsink or panel via screws. If you are operating near the 40A limit, we strongly recommend adding a heatsink to ensure optimal heat dissipation.
| Parameter | Value / Detail |
|---|---|
| Model | SSR-40DA |
| Input Control Voltage | 3–32V DC |
| Input Control Current | 3–25mA |
| Output Load Voltage | 24–380V AC |
| Maximum Output Current | 40A |
| Output Type | TRIAC |
| Switching Time | <10ms |
| Leakage Current (ON state) | <2mA |
| Dielectric Strength | 2500V AC |
| Insulation Resistance | 500MΩ / 500V DC |
| Isolation | Optical |
| Visual Indicator | LED ON |
| Operating Temperature | -30°C … +75°C |
| Dimensions | 6.5 × 5 × 2.5 cm |
| Mounting | Screw-mount |
Package Contents
- 1 × SSR-40DA Solid State Relay
Frequently Asked Questions
Can I use the SSR-40DA for DC loads?
No. The TRIAC output is designed exclusively for alternating current (AC) between 24V and 380V. If you need to switch DC loads, please select the SSR-DD model.
Does it work with Arduino or Raspberry Pi without extra components?
Yes. The control signal threshold starts at 3V DC, which is perfect for the 3.3V pins on a Raspberry Pi and the 5V pins on an Arduino. No additional transistors or resistors are required.
Is a heatsink mandatory for 40A operation?
Yes. At currents approaching the maximum rating, the relay generates significant heat. A suitable heatsink is essential to prevent overheating and ensure long-term stability.
Can it control a three-phase motor?
A single SSR-40DA controls one phase. To control a three-phase motor, you will need three identical relays, one for each phase.
Why is optical isolation important?
It provides complete electrical separation between your low-voltage control circuit (Arduino, PLC) and the high-voltage mains. If a voltage spike or short circuit occurs on the load side, your microcontrollers remain protected. The 2500V AC dielectric strength provides a significant safety margin.
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