How to Use SSR DC - DC: Examples, Pinouts, and Specs

The Fotek SSR DC-DC is a Solid State Relay (SSR) designed specifically for DC applications. It enables the control of high-voltage DC loads using low-voltage control signals. Unlike traditional mechanical relays, the SSR DC-DC offers fast switching, high reliability, and no mechanical wear, making it ideal for applications requiring frequent switching or long operational lifespans.

• Industrial automation systems
• Motor control in DC circuits
• Battery management systems
• Solar power systems
• LED lighting control
• Robotics and IoT devices

The following table outlines the key technical specifications of the Fotek SSR DC-DC:

The SSR DC-DC typically has four terminals. The table below describes each terminal:

1. Control Signal Connection:

   • Connect the positive control signal (3-32 V DC) to the + (Input) terminal.
   • Connect the ground of the control signal to the - (Input) terminal.

2. Load Connection:

   • Connect the positive side of the DC load to the + (Load) terminal.
   • Connect the negative side of the DC load to the - (Load) terminal.

3. Power Supply:

   • Ensure the load voltage and current do not exceed the SSR's rated output voltage (5-220 V DC) and current (40 A).

4. Mounting:

   • Secure the SSR to a heat sink or panel to ensure proper heat dissipation during operation.

5. Testing:

   • Apply the control signal voltage to the input terminals. The SSR should switch the load on or off depending on the control signal.

• Heat Dissipation: Use a heat sink or cooling fan if the SSR operates near its maximum current rating to prevent overheating.
• Isolation: Ensure proper electrical isolation between the control and load circuits to avoid damage.
• Polarity: Observe correct polarity for both the control signal and load connections.
• Surge Protection: Use a flyback diode across inductive loads (e.g., motors) to protect the SSR from voltage spikes.
• Testing: Avoid testing the SSR with a multimeter in continuity mode, as it may not provide accurate results for solid-state devices.

The SSR DC-DC can be controlled using an Arduino UNO. Below is an example circuit and code:

• Connect the Arduino's digital output pin (e.g., pin 9) to the + (Input) terminal of the SSR.
• Connect the Arduino's ground (GND) to the - (Input) terminal of the SSR.
• Connect the DC load to the + (Load) and - (Load) terminals of the SSR.

// Example code to control an SSR DC-DC with an Arduino UNO
// This code toggles the SSR on and off every 1 second.

#define SSR_PIN 9  // Define the Arduino pin connected to the SSR input

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

void loop() {
  digitalWrite(SSR_PIN, HIGH);  // Turn the SSR on (control signal HIGH)
  delay(1000);                  // Wait for 1 second
  digitalWrite(SSR_PIN, LOW);   // Turn the SSR off (control signal LOW)
  delay(1000);                  // Wait for 1 second
}

1. Can the SSR DC-DC be used with AC loads?

   • No, this SSR is designed specifically for DC loads. For AC loads, use an AC-AC or DC-AC SSR.

2. What happens if the control signal exceeds 32 V DC?

   • Exceeding the control voltage range may damage the SSR. Always stay within the specified range.

3. Is the SSR polarity-sensitive?

   • Yes, both the control and load terminals are polarity-sensitive. Incorrect polarity may damage the SSR or prevent it from functioning.

4. Can I use the SSR without a heat sink?

   • For low-current applications, a heat sink may not be necessary. However, for high-current loads, a heat sink is essential to prevent overheating.

By following this documentation, you can effectively integrate the Fotek SSR DC-DC into your projects and ensure reliable operation.