If you’re looking to explore the world of electronics, creating a relay control switch is a fantastic project. In this guide, we will walk you through building a simple relay switch circuit using the Y3F-SS-112DM relay, which is perfect for controlling various devices like lights, fans, or small motors.

What is the Y3F-SS-112DM?
The Y3F-SS-112DM is a miniature relay that operates with a coil voltage of 12V DC and can switch loads up to 10A at 250V AC or 30V DC. Its compact size and reliability make it suitable for various applications, from home automation to industrial control systems. The relay allows you to control high-voltage devices safely using low-voltage signals.

Components Needed
Required Components:
1 x Y3F-SS-112DM relay
1 x NPN transistor (e.g., 2N3904) (to drive the relay)
1 x diode (1N4001) (for flyback protection)
1 x resistor (1kΩ) (for base current limiting)
1 x toggle switch (to control the relay)
1 x 12V power supply
1 x load (like a lamp or small motor)
Breadboard and jumper wires
Optional Components:
LED indicator (to show relay status)
Heat sink (for the transistor if used continuously)
Circuit Diagram
Before assembling your project, it’s essential to have a clear understanding of the circuit layout. The Y3F-SS-112DM relay will be controlled by the NPN transistor, which acts as a switch to energize the relay coil.

Basic Connection Overview:
Connect the power supply to the relay coil and load.
Use the transistor to control the relay with a toggle switch.
Include a diode for protection against voltage spikes.
Step-by-Step Assembly
Step 1: Set Up the Breadboard
Insert the Y3F-SS-112DM relay into the breadboard. Identify the coil pins and the normally open (NO) and common (COM) contacts.
Step 2: Wiring the Power Supply
Connect the 12V power supply to one terminal of the relay coil.
Connect the other terminal of the relay coil to the collector of the NPN transistor.
Step 3: Adding the Diode
Place the 1N4001 diode across the relay coil terminals. The cathode (marked with a line) should be connected to the positive side of the relay coil, while the anode connects to the collector of the transistor. This diode prevents back EMF from damaging your circuit when the relay is turned off.
Step 4: Control Circuit Setup
Connect a 1kΩ resistor from the base of the NPN transistor to one terminal of the toggle switch.
Connect the other terminal of the toggle switch to the positive terminal of the 12V power supply.
Connect the emitter of the transistor to the ground.
Step 5: Connecting the Load
Wire the load (e.g., a lamp or small motor) to the NO terminal of the relay. Connect the COM terminal of the relay to the negative terminal of the power supply.
Step 6: Testing the Circuit
After ensuring all connections are secure, power on the circuit.
Toggle the switch to activate the relay. If everything is wired correctly, the load should turn on when the switch is closed.
Troubleshooting Tips
If the load does not activate, double-check all connections to ensure they match the diagram.
Verify that the power supply is functioning correctly and that the switch is making good contact.
Conclusion
Building a relay control switch using the Y3F-SS-112DM is a rewarding project that introduces you to essential concepts of relay operation, transistors, and circuit protection. This project provides a practical tool for controlling high-voltage devices safely and effectively. Once you are comfortable with this setup, consider expanding your project by integrating additional relays, using a microcontroller for automation, or adding more sophisticated controls. Happy building!