1. Introduction
The HiLetgo 5V 4 Channel Relay Shield is an electronic module designed to allow microcontrollers, such as the Arduino UNO R3, to control higher power electrical devices. It integrates four independent 5V relays onto a shield format, simplifying connections for various projects, including smart home applications and automation. This manual provides essential information for the proper setup, operation, and maintenance of your relay shield.
Figure 1: Angled view of the HiLetgo 5V 4 Channel Relay Shield, showing the four black relays, green terminal blocks, and pin headers.
2. Features
- Four Independent Relays: Equipped with four 5V relays (HJR-4102-L-5V) for controlling up to four separate electrical circuits.
- Arduino UNO R3 Compatibility: Standard shield form factor designed to directly plug into Arduino UNO R3 boards.
- Status Indicator LEDs: Each relay has a dedicated red LED that illuminates when the relay is activated, providing visual feedback.
- High Drive Capability: Supports control signals from 5V or 3.3V microcontrollers.
- Stackable Design: Allows for stacking with other compatible Arduino expansion boards.
- Mounting Holes: Includes three M3 screw positioning holes for secure installation.
3. Setup and Installation
Follow these steps to properly install your HiLetgo 5V 4 Channel Relay Shield onto an Arduino UNO R3 board:
- Prepare the Arduino Board: Ensure your Arduino UNO R3 board is powered off and disconnected from any power source.
- Align the Shield: Carefully align the male header pins on the underside of the relay shield with the corresponding female headers on your Arduino UNO R3 board. Ensure the orientation is correct.
- Mount the Shield: Gently press the relay shield down until all pins are fully seated in the Arduino headers. Avoid excessive force to prevent bending pins.
- Important Safety Precaution: The green terminal blocks on the relay shield may come into close proximity with the metal casing of the Arduino UNO's USB port. To prevent potential short circuits, it is highly recommended to place a piece of electrical tape over the metal casing of the Arduino's USB port before mounting the shield.
- Secure (Optional): If desired, use M3 screws to secure the relay shield to the Arduino board through the provided mounting holes.
Figure 2: The HiLetgo 5V 4 Channel Relay Shield mounted on an Arduino UNO R3 board, illustrating the stacked configuration.
4. Operating Instructions
This section details how to control the relays and connect external devices.
4.1 Relay Control Pins
The four relays are controlled by specific digital pins on the Arduino board:
- Relay 1: Controlled by Arduino Digital Pin 7
- Relay 2: Controlled by Arduino Digital Pin 6
- Relay 3: Controlled by Arduino Digital Pin 5
- Relay 4: Controlled by Arduino Digital Pin 4
To activate (turn ON) a relay, send a HIGH signal (e.g., 5V) to its corresponding control pin. To deactivate (turn OFF) a relay, send a LOW signal (e.g., 0V) to its control pin.
4.2 Relay Terminal Connections
Each of the four relays provides three terminals for connecting external devices:
- COMx (Common): This is the common terminal for the relay switch.
- NCx (Normally Closed): This terminal is connected to COMx when the relay is OFF (not activated).
- NOx (Normally Open): This terminal is connected to COMx when the relay is ON (activated).
When connecting an external device, typically one side of the device's power circuit is connected to COMx, and the other side is connected to either NCx (for normally ON behavior) or NOx (for normally OFF behavior) depending on your application requirements.
Figure 3: Top-down view of the relay shield, highlighting the labels for each relay (RELAY1-RELAY4) and their respective COM, NC, and NO terminals.
4.3 Power Supply
The relay shield draws its operating power (5V DC) directly from the Arduino board it is connected to. No external power supply is typically required for the shield itself, though the devices controlled by the relays will require their own power source.
5. Maintenance
The HiLetgo 5V 4 Channel Relay Shield is designed for reliable operation with minimal maintenance. To ensure longevity and proper function:
- Keep Clean: Periodically inspect the board for dust or debris and clean with a soft, dry brush if necessary. Avoid using liquids.
- Inspect Connections: Regularly check all terminal block connections to ensure wires are securely fastened and not loose.
- Environmental Conditions: Operate the shield within typical indoor environmental conditions, avoiding extreme temperatures, humidity, or corrosive atmospheres.
6. Troubleshooting
If you encounter issues with your relay shield, consider the following troubleshooting steps:
- Relay Not Activating:
- Verify the Arduino is powered on.
- Check that the correct digital pin is being used to control the relay (Pins 4, 5, 6, 7).
- Ensure a HIGH signal is being sent to the control pin.
- Confirm the relay's red indicator LED illuminates when activated. If not, there might be an issue with the control signal or the relay itself.
- External Device Not Switching:
- Ensure the relay is activating (check the LED).
- Verify the external device is correctly wired to the COMx and either NCx or NOx terminals.
- Check the external device's power supply and functionality independently of the relay.
- Inspect the terminal block screw connections for tightness and ensure wires are making good contact.
- Bent Pins: If the shield does not seat properly, carefully inspect the male header pins on the shield for any bends. Gently straighten them with small pliers or tweezers if necessary.
- Short Circuit with USB Port: If the Arduino or computer experiences unexpected behavior upon connecting the shield, immediately disconnect power. Re-check the installation and ensure the USB port's metal casing is insulated as described in Section 3.
- Intermittent Operation: Loose connections, cold solder joints (though less common for new products), or insufficient power can cause intermittent operation. Re-check all connections and power supply.
7. Specifications
| Feature | Specification |
|---|---|
| Brand | HiLetgo |
| Model Number | 8541582938 |
| Coil Voltage | 5 Volts DC |
| Maximum Switching Voltage | 5 Volts |
| Minimum Switching Voltage | 5 Volts (DC) |
| Contact Type | Normally Closed, Normally Open |
| Contact Material | Silver |
| Connector Type | Plug-In (for Arduino), Screw Mount (for external devices) |
| Mounting Type | Screw Mount (for shield itself) |
| Operation Mode | Automatic |
| Item Weight | 2.39 ounces |
| Package Dimensions | 4.76 x 3.15 x 1.46 inches |
| Color | Blue |
8. Safety Information
Please observe the following safety guidelines when using the HiLetgo 5V 4 Channel Relay Shield:
- Electrical Shock Hazard: Relays are used to switch electrical currents. Always ensure power is disconnected from both the Arduino and any external devices before making or changing connections.
- USB Port Short Circuit: As noted in Section 3, insulate the metal casing of the Arduino UNO's USB port with electrical tape to prevent accidental short circuits with the relay shield's terminal blocks.
- Voltage and Current Ratings: Do not exceed the maximum voltage and current ratings of the relays (e.g., 3A at 125VAC or 3A at 24VDC for the HJR-4102-L-5V relays). Exceeding these ratings can damage the module and pose a fire hazard.
- Proper Wiring: Ensure all wiring is secure and correctly connected. Loose connections can lead to arcing, overheating, and potential fire.
- Supervision: Do not leave high-power relay circuits unattended, especially during initial testing.
- Intended Use: This product is intended for hobbyist and educational use in controlling low-power devices within specified limits. It is not designed for critical safety systems or high-power industrial applications without additional safety measures.
9. Warranty and Support
For technical support or if you encounter any issues with your HiLetgo 5V 4 Channel Relay Shield, please contact HiLetgo customer support directly.
Email: support@hiletgo.com
Please refer to the official HiLetgo website or your purchase documentation for specific warranty terms and conditions.
