How to Use SSR-25DA 25A 250V Solid State Relay Module: Examples, Pinouts, and Specs

Image of SSR-25DA 25A 250V Solid State Relay Module

Design with SSR-25DA 25A 250V Solid State Relay Module in Cirkit Designer

Introduction

The SSR-25DA is a solid state relay (SSR) manufactured by HiLetgo (Part ID: 3-01-1247-25A). This relay is designed to switch AC loads of up to 25A at 250V using a low-voltage DC control signal. Unlike traditional mechanical relays, the SSR-25DA uses semiconductor devices for switching, offering faster response times, silent operation, and a longer lifespan.

Explore Projects Built with SSR-25DA 25A 250V Solid State Relay Module

PID Temperature Control System with Thermocouple and SSR

This circuit is a temperature control system that uses a thermocouple to measure temperature and a PID controller to regulate it. The PID controller drives a solid-state relay (SSR) to control an external load, with power supplied through an AC inlet socket.

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Temperature-Controlled Heating System with SSR and Titanium Resistor

This circuit is a temperature control system that uses a temperature controller to regulate a heating titanium resistor via a solid-state relay (SSR). The power transformer supplies the necessary voltage to the temperature controller, which in turn controls the SSR to manage the heating element.

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DC-DC Converter and Relay Module Power Distribution System

This circuit consists of a DC-DC converter powering a 6-channel power module, which in turn supplies 5V to a 2-relay module. The power module distributes the converted voltage to the relay module, enabling it to control external devices.

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Arduino Mega 2560 Controlled Automation System with 8-Channel Relay and Nextion Touch LCD Interface

This circuit is centered around an Arduino Mega 2560, which controls a Nextion Touch LCD for user interface and a series of relays for switching various loads. The Arduino is powered by a 9V SMPS, and it drives an 8-channel 5V relay module to control devices like pumps, a loudspeaker, actuators, a heating plate, and a plucker. The relays are interfaced with solid-state relays (SSRs) and a thermistor for temperature sensing, enabling controlled power distribution to the connected devices based on programmed logic and user input.

Open Project in Cirkit Designer

Common Applications

Industrial automation and control systems
Heating, ventilation, and air conditioning (HVAC) systems
Motor control and lighting systems
Home automation projects
Arduino and microcontroller-based projects for controlling high-power AC devices

Technical Specifications

Key Specifications

Parameter	Value
Manufacturer	HiLetgo
Part ID	3-01-1247-25A
Load Voltage Range	24V AC to 250V AC
Load Current Rating	25A
Control Voltage Range	3V DC to 32V DC
Control Current	≤ 25mA
Trigger Voltage (ON)	≥ 3V DC
Trigger Voltage (OFF)	≤ 1V DC
Isolation Voltage	2500V AC
Switching Type	Zero-crossing
Operating Temperature	-30°C to +75°C
Dimensions	58mm x 45mm x 23mm
Weight	~110g

Pin Configuration and Descriptions

The SSR-25DA has four terminals, divided into two sections: the control side and the load side.

Control Side (Input Terminals)

Pin	Label	Description
1	+	Positive DC control signal (3V to 32V DC)
2	-	Negative DC control signal (ground)

Load Side (Output Terminals)

Pin	Label	Description
3	~	AC load terminal 1 (connect to AC load)
4	~	AC load terminal 2 (connect to AC load)

Usage Instructions

How to Use the SSR-25DA in a Circuit

Control Side Connection:
- Connect the positive control signal (e.g., from a microcontroller or Arduino) to the + terminal.
- Connect the ground of the control signal to the - terminal.
- Ensure the control voltage is within the range of 3V to 32V DC.
Load Side Connection:
- Connect one terminal of the AC load to one of the ~ terminals on the SSR.
- Connect the other ~ terminal to the AC power source.
- Ensure the load does not exceed the maximum rating of 25A at 250V AC.
Powering the Circuit:
- When the control signal voltage is applied (≥ 3V DC), the SSR will switch ON, allowing current to flow through the load.
- When the control signal voltage is removed (≤ 1V DC), the SSR will switch OFF, stopping current flow.

Important Considerations and Best Practices

Heat Dissipation: The SSR-25DA generates heat during operation. Use a heatsink or mount the relay on a metal surface to ensure proper heat dissipation, especially for high-current loads.
Isolation: Ensure proper electrical isolation between the control and load sides to prevent damage to the control circuit.
Zero-Crossing Switching: The SSR-25DA uses zero-crossing technology, which minimizes electrical noise and extends the lifespan of connected devices.
Overcurrent Protection: Use a fuse or circuit breaker to protect the relay and load from overcurrent conditions.
Avoid Inductive Loads: For inductive loads (e.g., motors), use a snubber circuit to suppress voltage spikes.

Example: Using SSR-25DA with Arduino UNO

Below is an example of how to control an AC light bulb using the SSR-25DA and an Arduino UNO.

Circuit Diagram

Connect the Arduino's digital pin (e.g., pin 9) to the + terminal of the SSR.
Connect the Arduino's GND to the - terminal of the SSR.
Connect the AC light bulb to the load side of the SSR as described above.

Arduino Code

// Define the pin connected to the SSR control terminal
const int ssrPin = 9;

void setup() {
  pinMode(ssrPin, OUTPUT); // Set the SSR pin as an output
}

void loop() {
  digitalWrite(ssrPin, HIGH); // Turn ON the SSR (AC load ON)
  delay(5000);               // Keep the load ON for 5 seconds
  digitalWrite(ssrPin, LOW);  // Turn OFF the SSR (AC load OFF)
  delay(5000);               // Keep the load OFF for 5 seconds
}

Note: Ensure proper safety precautions when working with AC mains voltage. Disconnect power before making any connections.

Troubleshooting and FAQs

Common Issues and Solutions

Issue	Possible Cause	Solution
SSR does not turn ON	Control voltage is too low	Ensure control voltage is ≥ 3V DC
SSR remains ON even without signal	Faulty SSR or incorrect wiring	Check wiring and replace the SSR if needed
Excessive heat during operation	High load current or poor heat dissipation	Use a heatsink or reduce load current
Load does not turn OFF	Inductive load causing voltage spikes	Add a snubber circuit across the load

FAQs

Can the SSR-25DA be used with DC loads?
- No, the SSR-25DA is designed for AC loads only. For DC loads, use a DC-specific SSR.
What happens if the load exceeds 25A?
- Exceeding the rated current can damage the SSR. Always use a fuse or circuit breaker for protection.
Is the SSR-25DA suitable for dimming applications?
- No, the SSR-25DA is not designed for phase control or dimming. Use a dimmer-specific SSR for such applications.
Can I use the SSR-25DA without a heatsink?
- For low-current loads, a heatsink may not be necessary. However, for high-current loads, a heatsink is essential to prevent overheating.

By following this documentation, you can safely and effectively use the SSR-25DA in your projects.