Weasch SRD-24VDC-SL-C PCB Power Relay User Manual

1. Product Overview

The Weasch SRD-24VDC-SL-C PCB Electromagnetic Power Relay is a versatile component designed for automatic adjustment, circuit protection, and transformation. It features 5 pins and is widely utilized in remote control systems, communication equipment, automatic control systems, and a broad range of electronic devices.

Its functionality extends to controlling small motors, incandescent lamps, indicator lights, low-power power supplies, intelligent instrumentation, and various solenoid valves. Furthermore, it can serve as a crucial component for driving high-power electromagnetic contactors, making it an essential part of many household appliance boards and industrial setups.

2. Specifications

Figure 1: Detailed dimensions of the SRD-24VDC-SL-C relay, showing its compact size suitable for PCB mounting. The relay measures 0.75 inches (19mm) in length, 0.59 inches (15mm) in width, and 0.67 inches (17mm) in height.

3. Setup and Installation

The SRD-24VDC-SL-C relay is designed for direct mounting onto a Printed Circuit Board (PCB). Proper installation is crucial for safe and reliable operation.

3.1 Safety Precautions

• Always disconnect power to the circuit before installing or removing the relay.
• Ensure that the relay's specifications (voltage, current, contact capacity) match the requirements of your application.
• Handle the relay by its body to avoid bending or damaging the pins.
• If you are unsure about any aspect of the installation, consult a qualified electrician or electronics technician.

3.2 Mounting Instructions

1. Identify the correct orientation for the relay on the PCB. The relay typically has a marking or notch indicating pin 1 or the coil side.
2. Carefully align the 5 pins of the relay with the corresponding holes on the PCB.
3. Gently push the relay into place until it sits flush with the PCB surface.
4. Solder the pins to the PCB pads using appropriate soldering techniques. Ensure good solder joints for reliable electrical connection.

Figure 2: Left image shows the bottom view of the relay, highlighting the 5 pins and the coil trace. Right image displays two relays, one upright and one inverted, illustrating both the top markings and the pin configuration for proper PCB insertion.

3.3 Wiring Connections

The SRD-24VDC-SL-C is a SPDT (Single Pole Double Throw) relay, meaning it has one common contact that can switch between two other contacts (Normally Open - NO, and Normally Closed - NC).

• Coil Pins: These pins are for the DC 24V coil. When 24VDC is applied across these pins, the coil energizes, causing the contacts to switch.
• Common (COM) Pin: This is the input or common connection for the switched circuit.
• Normally Open (NO) Pin: This contact is open (no connection) when the coil is de-energized and closes when the coil is energized.
• Normally Closed (NC) Pin: This contact is closed (connected) when the coil is de-energized and opens when the coil is energized.

Refer to the circuit diagram of your application for specific wiring requirements. Ensure all connections are secure and insulated to prevent short circuits.

Figure 3: Top view of the SRD-24VDC-SL-C relay, clearly showing the model number, coil voltage, and contact ratings. This view also displays the CQC and cURus certifications.

4. Operating Principles

The SRD-24VDC-SL-C is an electromagnetic relay that operates on the principle of electromagnetism. When a DC 24V voltage is applied to the coil pins, an electromagnetic field is generated. This field attracts an armature, causing the internal contacts to switch their state.

• De-energized State: When no voltage is applied to the coil, the common (COM) contact is connected to the Normally Closed (NC) contact. The Normally Open (NO) contact remains disconnected.
• Energized State: When DC 24V is applied to the coil, the common (COM) contact switches its connection from the NC contact to the Normally Open (NO) contact.

This switching action allows the relay to control a separate, higher-power or different-voltage circuit using a low-power control signal from the coil. It provides electrical isolation between the control circuit and the switched circuit.

5. Maintenance

PCB power relays like the SRD-24VDC-SL-C are generally low-maintenance components. However, adhering to a few guidelines can help ensure their longevity and reliable performance:

• Environmental Conditions: Ensure the relay operates within its specified temperature and humidity ranges. Avoid exposure to excessive dust, moisture, or corrosive environments.
• Cleanliness: Keep the area around the relay clean and free from debris that could interfere with its operation or cause short circuits.
• Connection Integrity: Periodically inspect the solder joints and connections to the relay pins to ensure they remain secure and free from corrosion. Loose connections can lead to overheating or intermittent operation.
• Load Management: Do not exceed the relay's maximum contact capacity (10A 250VAC/125VAC/30VDC/28VDC). Overloading can cause premature wear or failure of the contacts.

If the relay shows signs of damage or malfunction, it should be replaced immediately by a qualified technician.

6. Troubleshooting

If you encounter issues with your SRD-24VDC-SL-C relay, consider the following troubleshooting steps:

6.1 Relay Not Switching

• Check Coil Voltage: Verify that the correct DC 24V is being applied to the coil pins when the relay is supposed to energize. Use a multimeter to measure the voltage.
• Coil Continuity: With power disconnected, check the resistance across the coil pins. An open circuit (infinite resistance) indicates a faulty coil.
• Wiring: Inspect all wiring connections to ensure they are secure and correctly connected according to your circuit diagram.

6.2 Contacts Not Making/Breaking Properly

• Load Current: Ensure the current flowing through the contacts does not exceed the relay's rated capacity (10A). Overcurrent can cause contact welding or pitting.
• Contact Condition: While difficult to inspect on a sealed relay, repeated arcing from inductive loads or excessive current can degrade contacts over time.
• Coil Voltage (again): Insufficient coil voltage might lead to weak contact closure.

6.3 Intermittent Operation

• Loose Connections: Re-solder or tighten any loose connections on the PCB or to the relay pins.
• Vibration: In high-vibration environments, ensure the relay is securely mounted and connections are strain-relieved.
• Power Supply Fluctuations: Unstable power supply to the coil can cause erratic switching.

If troubleshooting steps do not resolve the issue, the relay may be faulty and require replacement.

7. Warranty and Support

For specific warranty information regarding your Weasch SRD-24VDC-SL-C PCB Power Relay, please refer to the purchase documentation or contact the seller directly. Weasch is committed to providing quality products and customer satisfaction.

For further support, product inquiries, or to explore other Weasch products, please visit the official Weasch store:

Visit the Weasch Store

8. Product Images

Image 4: A pair of Weasch SRD-24VDC-SL-C PCB Power Relays, showcasing their standard blue casing and pin configuration.

Image 5: Side profile of a single SRD-24VDC-SL-C relay, highlighting its compact form factor and the arrangement of its pins.