How to Use ZK-502L: Examples, Pinouts, and Specs

The ZK-502L, manufactured by Walfront, is a compact, low-power relay designed for efficient switching in electronic circuits. It features a Single Pole Double Throw (SPDT) configuration, enabling it to control multiple circuits with a single input signal. This relay is ideal for applications requiring reliable switching with minimal power consumption.

• Home automation systems
• Industrial control panels
• Motor control circuits
• Signal switching in low-power devices
• DIY electronics and prototyping

The ZK-502L relay has 5 pins. Below is the pinout and description:

1. Power the Relay Coil: Connect the Coil (+) pin to a 5V DC power source and the Coil (-) pin to ground. This energizes the relay coil and switches the contacts.
2. Connect the Load:
   • For devices that should turn on when the relay is activated, connect the load between the Common (COM) and Normally Open (NO) pins.
   • For devices that should turn off when the relay is activated, connect the load between the Common (COM) and Normally Closed (NC) pins.
3. Control the Relay: Use a microcontroller (e.g., Arduino UNO) or a manual switch to control the relay coil.

• Diode Protection: Always connect a flyback diode (e.g., 1N4007) across the relay coil to protect the circuit from voltage spikes when the relay is de-energized.
• Power Ratings: Ensure the load connected to the relay does not exceed its maximum voltage (250V AC / 30V DC) or current (10A) ratings.
• Isolation: Use optocouplers or transistors to isolate the relay from sensitive control circuits if needed.
• Mounting: Secure the relay on a PCB or relay socket to ensure stable operation.

Below is an example of how to control the ZK-502L relay using an Arduino UNO:

// Example: Controlling ZK-502L Relay with Arduino UNO

const int relayPin = 7; // Pin connected to the relay's Coil (+)

void setup() {
  pinMode(relayPin, OUTPUT); // Set relay pin as output
  digitalWrite(relayPin, LOW); // Ensure relay is off at startup
}

void loop() {
  digitalWrite(relayPin, HIGH); // Activate the relay
  delay(1000); // Keep relay on for 1 second
  digitalWrite(relayPin, LOW); // Deactivate the relay
  delay(1000); // Keep relay off for 1 second
}

Note: Use a transistor (e.g., 2N2222) to drive the relay if the Arduino pin cannot supply sufficient current.

1. Relay Not Activating:

   • Cause: Insufficient voltage or current to the relay coil.
   • Solution: Verify the power supply provides 5V DC and sufficient current (at least 72mA).

2. Voltage Spikes Damaging Circuit:

   • Cause: Lack of a flyback diode across the relay coil.
   • Solution: Install a flyback diode (e.g., 1N4007) across the coil terminals.

3. Load Not Switching Properly:

   • Cause: Incorrect wiring of the load to the relay pins.
   • Solution: Double-check the connections to the COM, NO, and NC pins.

4. Relay Heating Up:

   • Cause: Exceeding the relay's power or current ratings.
   • Solution: Ensure the load does not exceed 10A or the specified voltage limits.

Q1: Can the ZK-502L relay be used with a 3.3V control signal?
A1: No, the ZK-502L requires a 5V DC control signal to activate the coil. Use a level shifter or transistor to interface with 3.3V systems.

Q2: Is the ZK-502L suitable for high-frequency switching?
A2: No, mechanical relays like the ZK-502L are not designed for high-frequency switching. Consider using a solid-state relay (SSR) for such applications.

Q3: Can I use the ZK-502L to switch AC loads?
A3: Yes, the ZK-502L can switch AC loads up to 250V, provided the current does not exceed 10A.

Q4: How do I know if the relay is activated?
A4: You can hear a clicking sound when the relay switches. Alternatively, you can measure continuity between the COM and NO pins to confirm activation.