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 mechatronics

The Fotek SSR DC - DC is engineered to handle a wide range of DC loads with precision and efficiency. Below are the key technical details:

The SSR DC - DC typically has four terminals, as described in the table below:

1. Connect the Control Signal:

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

2. Connect the Load:

   • 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 the Circuit:

   • Ensure the control signal voltage is within the specified range (3-32 VDC).
   • When the control signal is applied, the SSR will switch the DC load on.

4. Mounting:

   • Secure the SSR to a heat sink or panel using screws to ensure proper heat dissipation.

• Heat Dissipation: Ensure adequate heat sinking or ventilation to prevent overheating during operation.
• Polarity: Observe correct polarity for both the control signal and the load connections.
• Load Type: The SSR DC - DC is designed for resistive or low-inductive DC loads. Avoid using it with high-inductive loads without proper snubber circuits.
• Switching Speed: The SSR is not suitable for high-frequency switching applications.
• Isolation: Ensure proper electrical isolation between the control and load circuits to prevent damage.

Below is an example of how to control a DC load using the Fotek SSR DC - DC and an Arduino UNO:

// Example: Controlling a DC load with Fotek SSR DC - DC and Arduino UNO

const int ssrPin = 9; // Pin connected to the SSR control input

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

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

Note: Ensure the Arduino's ground is connected to the SSR's - (Input) terminal.

1. SSR Not Switching the Load:

   • Cause: Insufficient control voltage or incorrect wiring.
   • Solution: Verify that the control voltage is within the 3-32 VDC range and check the wiring.

2. Overheating:

   • Cause: Inadequate heat dissipation or excessive load current.
   • Solution: Use a heat sink or fan to improve cooling. Ensure the load current does not exceed the SSR's maximum rating.

3. Load Not Turning Off:

   • Cause: Leakage current in the SSR.
   • Solution: Use a bleeder resistor across the load to dissipate the leakage current.

4. Control Signal Not Detected:

   • Cause: Faulty control signal or damaged SSR.
   • Solution: Check the control signal voltage and replace the SSR if necessary.

• Double-check all connections for proper polarity and secure contacts.
• Use a multimeter to measure the control voltage and load voltage.
• If the SSR fails to operate, test it with a known working control signal and load to isolate the issue.
• Avoid exceeding the SSR's voltage and current ratings to prevent permanent damage.

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