| | Likely Cause | Solution | |-------------|------------------|---------------| | Relay does not click | No power on VCC | Check 5V and GND connections. | | Relay clicks but load doesn’t turn on | Wrong wiring (NC vs NO) | Load should be connected to COM and NO. | | Random toggling | Floating input pin | Use a pull-down (active HIGH) or pull-up (active LOW) resistor (10kΩ). | | Microcontroller resets when relay activates | Power supply insufficient | Relay coil draws ~80mA. Use a separate 5V supply for module. | | Jumper setting ignored | Poor contact | Remove/insert jumper multiple times or solder the desired connection. | 8. YL105 vs. Other Relay Modules How does the YL105 compare to similar modules?
Introduction In the world of electronics and microcontroller projects (Arduino, Raspberry Pi, ESP8266, STM32), the ability to control high-power devices—such as lamps, motors, solenoids, and pumps—using low-power logic signals is essential. The YL105 is one of the most popular and widely available single-channel relay modules designed precisely for this purpose.
| | Min | Typ | Max | Unit | |---------------|---------|---------|---------|----------| | Supply Voltage (VCC) | 4.5 | 5.0 | 5.5 | V DC | | Input High Voltage (IN - HIGH mode) | 3.0 | 5.0 | 5.5 | V | | Input Low Voltage (IN - LOW mode) | 0 | 0.8 | 1.5 | V | | Input Current (IN pin) | – | 5 | 15 | mA | | Relay Coil Current | – | 70 | 90 | mA | | Total Module Current | – | 85 | 110 | mA | Relay Contact Ratings (Load Side) | Load Type | Voltage | Max Current | |---------------|-------------|------------------| | Resistive AC | 250V AC | 10A | | Resistive DC | 30V DC | 10A | | Inductive AC | 250V AC | 7A | | Inductive DC | 30V DC | 5A | Warning: Do not exceed these ratings. The relay may weld shut or catch fire. 4. Timing Characteristics (Switching Speed) For applications requiring high-speed switching (e.g., dimming, pulse control), the relay’s mechanical nature limits operation. Refer to these timing specs: yl105 datasheet
If the jumper is installed, the relay activates when IN = LOW. The wiring is identical, but logic is reversed.
| | YL105 | SRD-05VDC-SL-C (bare relay) | KY-019 | Songle 1-channel | |-------------|-----------|--------------------------------|------------|----------------------| | Opto-isolated | Yes | No | Yes | Yes | | Active LOW/HIGH selectable | Yes (jumper) | No | Fixed HIGH | Fixed LOW | | LED indicators | Power + Status | None | Power + Status | Power + Status | | Screw terminals | Yes (3 pins) | No | Yes (3 pins) | Yes (3 pins) | | Typical price | $2–$4 | $1 | $3–$5 | $2–$4 | | | Microcontroller resets when relay activates |
Whether you are automating your home, building a robot, or designing a safety cutoff, the YL105 offers a reliable bridge between the fragile world of microcontrollers and the demanding realm of high-power electronics. Always respect the voltage ratings, adhere to proper wiring practices, and consult the SRD-05VDC-SL-C and PC817 datasheets for deeper technical insight.
void loop() digitalWrite(relayPin, HIGH); // turn relay ON delay(2000); digitalWrite(relayPin, LOW); // turn relay OFF delay(2000); Always respect the voltage ratings
When working with AC mains voltage (110V/230V), take all necessary safety precautions. Use insulated enclosures, avoid live testing, and never leave the module powered while unattended. Need more technical specifics? Leave a comment or refer to the component-level datasheets linked in Section 9. Happy switching!