Product Overview
The 5V 1 Way Solid State Relay (SSR) is a high-performance, semiconductor-based switching device designed to control AC loads using a low-voltage DC control signal. Unlike traditional electromagnetic relays that rely on moving mechanical contacts, this SSR uses phototriac isolation technology—an infrared LED and a phototriac sealed in a compact package—to switch high-voltage AC loads silently, without any moving parts .
This module is specifically designed for DC control of AC loads. It accepts a 5V DC control signal from microcontrollers like Arduino, ESP32, or Raspberry Pi, and switches AC loads up to 240V at 2A . The module features zero-crossing switching, meaning it only turns on when the AC load voltage crosses zero volts, minimizing electrical noise and reducing stress on connected devices .
A key feature of this SSR module is its flexibility—it is available in both High Level Trigger (relay activates when control pin is HIGH) and Low Level Trigger (relay activates when control pin is LOW) versions. The low-level trigger version is often preferred for safety, as the relay remains off during power-up or if the control signal is lost .
Unlike mechanical relays, SSRs offer silent operation, faster switching speeds, no contact wear or arcing, and significantly longer lifespan . They are ideal for controlling lighting, heating elements, fans, small motors, and other AC-powered devices in home automation, industrial control, and IoT projects .
Key Features
-
Solid State Switching: Uses phototriac isolation with zero-crossing detection for silent, spark-free operation with no moving parts to wear out .
-
AC Load Control: Designed to switch AC loads up to 240V at 2A (resistive). Suitable for lights, fans, heaters, and small motors .
-
5V DC Control: Accepts standard 5V logic signals from Arduino, ESP32, STM32, and other microcontrollers .
-
Selectable Trigger Mode: Available in both High Level Trigger (active HIGH) and Low Level Trigger (active LOW) versions to match your application needs .
-
Optical Isolation: Fully isolates the low-voltage control side from the high-voltage AC load side for enhanced safety and noise immunity .
-
Built-in Snubber Circuit: Includes an internal RC snubber to protect against voltage spikes and reduce EMI when switching inductive loads .
-
Status Indicator LED: Onboard LED provides clear visual confirmation of relay activation status.
-
Fuse Protection: Many modules include a replaceable 2A/240V slow-blow fuse for overload and short-circuit protection .
-
Compact PCB Design: Small footprint (approx. 34×25×25mm) with screw terminals for easy wiring and mounting .
Technical Specifications
Pinout & Interface Guide
Input Side (Control Interface)
Trigger Mode Selection:
Output Side (Load Terminals)
Important Wiring Note
This SSR switches the live (hot) wire of the AC circuit. The AC neutral must be connected directly to the load’s neutral terminal. Do not connect the SSR output directly across the AC line without a load .
Usage Guide
Wiring Instructions
IMPORTANT: Always disconnect AC mains power before wiring high-voltage loads.
Basic Connection (Control Side)
AC Load Connection
-
Connect the Live (L) wire from your AC source to the AC IN terminal
-
Connect your AC load (lamp, fan, heater) to the AC LOAD terminal
-
Connect the load’s Neutral (N) wire directly to the AC source neutral
Fuse Protection
The module includes a 2A/240V slow-blow fuse for overload protection . If the fuse blows, replace it with an identical type before resuming operation.
Control Logic Examples
High Level Trigger Version:
Low Level Trigger Version:
Example Arduino Code (High Level Trigger)
const int relayPin = 7;
void setup() {
pinMode(relayPin, OUTPUT);
digitalWrite(relayPin, LOW);
}
void loop() {
digitalWrite(relayPin, HIGH);
delay(5000);
digitalWrite(relayPin, LOW);
delay(5000);
}
Example Arduino Code (Low Level Trigger)
const int relayPin = 7;
void setup() {
pinMode(relayPin, OUTPUT);
digitalWrite(relayPin, HIGH);
}
void loop() {
digitalWrite(relayPin, LOW);
delay(5000);
digitalWrite(relayPin, HIGH);
delay(5000);
}
Important Considerations
-
AC Load Only: This SSR is designed for AC loads only. Do not use it to switch DC loads .
-
Zero-Crossing Switching: The SSR uses zero-crossing detection, meaning it only turns on when the AC voltage crosses zero. This reduces electrical noise but introduces a slight delay (up to 8.33ms at 60Hz) .
-
Minimum Load Current: Some SSRs require a minimum load current (typically 10mA) to function properly. Very light loads may not trigger reliably .
-
Testing Limitations: You cannot reliably test an SSR with a standard multimeter continuity test, as the multimeter’s test voltage is insufficient to trigger the phototriac .
Q: What is the difference between a Solid State Relay (SSR) and an electromagnetic relay (EMR)?
An SSR uses semiconductor components (phototriac) to switch loads with no moving parts, offering silent operation, faster switching, and longer lifespan. An EMR uses a mechanical coil and moving contacts, which can wear out over time and produce audible clicking .
Q: Can I use this SSR to switch DC loads?
No. This module is specifically designed for AC loads only. The internal phototriac is designed to turn off when the AC current crosses zero. For DC loads, use a DC-controlled DC SSR or a mechanical relay .
Q: What is the maximum load this SSR can handle?
The module is rated for 2A at up to 240V AC for resistive loads . For inductive loads like motors, derate to 1A–1.5A to account for startup surges.
Q: What is zero-crossing switching?
Zero-crossing switching means the SSR only turns on when the AC voltage crosses zero volts. This minimizes electrical noise, reduces inrush current, and protects sensitive loads .
Q: Can I use this SSR with a 3.3V microcontroller like ESP32 or Raspberry Pi?
Yes. The control signal threshold for High Level Trigger version is 3.3V–5V, making it directly compatible with 3.3V logic . For Low Level Trigger version, the LOW signal (0V) works regardless of logic voltage.
Q: What power supply do I need for this module?
The module requires a stable 5V DC supply capable of providing at least 20mA. The typical control current is 12.5mA–16mA .
Q: Why does my SSR not turn on when I test it with a multimeter?
A standard multimeter cannot generate enough voltage to trigger the phototriac inside the SSR. The SSR requires an actual AC load connected to function properly .
Q: Does the SSR have a built-in fuse?
Many versions include a 2A/240V slow-blow fuse for overload protection . If the fuse blows, replace it with an identical type.
Q: The load stays on even when the control signal is OFF. What's wrong?
This can happen with very light loads (e.g., <10mA) because the internal snubber circuit may pass a small leakage current. The SSR is designed for loads above this threshold .
Q: Can I use this SSR for 220V AC applications?
Yes. The module is rated for up to 264V AC, making it suitable for 220V/240V systems .
Q: Do I need a heatsink for this SSR?
For 2A continuous load, a heatsink is not typically required due to the module’s low power dissipation. However, ensure adequate airflow around the module .
Q: Why does my SSR have a delay when turning on/off?
The zero-crossing detection introduces a slight delay (up to one half-cycle of AC, approx. 8.33ms at 60Hz) to turn on . This is normal and prevents electrical noise.
Q: Can I use multiple SSR modules with a single microcontroller?
Yes. Connect each module’s DC+ and DC- in parallel to the same 5V supply (ensure the supply can handle the total current), and connect each CH pin to a separate digital output pin.
Q: What can I build with this 5V Solid State Relay?
Popular applications include:
-
Home automation: Control lights, fans, and appliances with Arduino/ESP32
-
Industrial control: Switching heating elements, pumps, and solenoids
-
IoT projects: Remote AC load control with ESP8266/ESP32
-
Lighting systems: Dimming and switching for holiday lights and displays
Q: Is this SSR suitable for controlling a motor?
Yes, with derating. For motor loads, it is recommended to operate at 50–70% of the rated current (1A–1.4A) to account for startup surges. The zero-crossing feature helps reduce inrush current .
Q: Can I use this SSR for phase control (dimmable lighting)?
No. This SSR uses zero-crossing switching, which is designed for on/off control only. For phase control (dimmable lighting), you need an SSR without zero-crossing detection, such as the Omron G3MB-202PL .
Q: How long does an SSR last compared to a mechanical relay?
SSRs have a significantly longer lifespan than mechanical relays due to the absence of moving contacts. They can handle millions of switching cycles, making them ideal for frequent switching applications .
