Product Overview
The BESTEP 1-Way Electromagnetic Relay Module is a high-performance, industrial-grade control module designed to provide a safe and reliable interface between low-voltage logic circuits and high-power devices. Operating at 24V DC, this module is ideally suited for PLC automation systems, industrial control panels, building automation, and 24V industrial equipment .
Featuring dual optocoupler isolation, this module creates a robust physical and electrical barrier between your sensitive microcontroller (such as Arduino, STM32, or ESP32) and the high-voltage load side. This effectively eliminates electrical noise, protects against back-EMF spikes from motors and solenoids, and ensures system stability in demanding industrial environments .
This versatile module supports both High-Level and Low-Level Trigger modes, selectable via an onboard jumper, making it compatible with virtually any digital logic system without the need for external level shifters. With a relay contact rating of 30A at 250V AC or 30A at 30V DC, it can handle substantial loads, including heavy-duty motors, industrial pumps, compressors, and high-power lighting systems .
Key Features
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30A High-Power Switching: Relay contacts rated for 30A at 250V AC or 30A at 30V DC, suitable for heavy-duty industrial equipment, motors, and high-power appliances .
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Dual Optocoupler Isolation: Features two optocouplers providing enhanced electrical isolation between the control side and the high-voltage load side, ensuring superior noise immunity and protection against voltage spikes .
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24V DC Operation: Designed for 24V industrial control systems, making it ideal for PLC automation, building management systems, and industrial controllers .
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Universal Trigger Modes: Supports both High Level (Active HIGH) and Low Level (Active LOW) trigger modes, selectable via an onboard jumper, allowing compatibility with any microcontroller or PLC logic system .
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SPDT Contact Configuration: Provides Common (COM), Normally Open (NO), and Normally Closed (NC) terminals for maximum wiring flexibility .
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Fault-Tolerant Design: Even if the control line is disconnected or broken, the relay will not operate unintentionally, ensuring fail-safe behavior in critical applications .
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Clear Status Indicators: Onboard LEDs provide visual feedback: a green power LED illuminates when 24V power is applied, and a red relay status LED illuminates when the relay is activated .
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Compact and Mountable: Small form factor with four 3.1mm mounting holes (44.5mm × 27.5mm spacing) for secure installation in control cabinets or on DIN rails .
Technical Specifications
Pinout & Interface Guide
Input Side (Control Interface)
Output Side (Load Terminals)
Jumper Settings
JD-VCC Power Jumper
The JD-VCC jumper (connecting DC+ to JD+) allows the relay coil to share the same 24V supply as the control logic. For applications requiring complete isolation, remove the jumper and supply 24V separately to JD+ and JD- .
Status LEDs
Usage Guide
Wiring Instructions
IMPORTANT: Always disconnect mains power before wiring high-voltage loads.
Basic Connection (Control Side)
Load Connection (AC Example)
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Connect the Live (L) wire from your AC source to the COM terminal
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Connect the load (motor, pump, lighting) to the NO terminal for OFF-by-default operation
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Connect the load’s Neutral (N) wire directly to the AC source neutral
Load Connection (DC Example)
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Connect the positive (+) supply to the COM terminal
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Connect the load’s positive wire to the NO terminal
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Connect the load’s negative wire directly to the power supply ground
Setting the Trigger Mode
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High Level Trigger (Active HIGH): Place the jumper on the H position. The relay activates when the IN pin is HIGH (3.3V–24V) .
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Low Level Trigger (Active LOW): Place the jumper on the L position. The relay activates when the IN pin is LOW (0V) .
Note: Low Level Trigger is ideal for fail-safe applications where the relay should remain OFF if the control signal is lost .
Example PLC Ladder Logic Concept
For PLC control, a normally open contact can be used to energize an output coil connected to the relay module’s IN terminal. When the contact closes, the output goes LOW (active for Low Level Trigger) or HIGH (active for High Level Trigger), activating the relay.
Example Arduino Code (High Level Trigger)
const int relayPin = 7;
void setup() {
pinMode(relayPin, OUTPUT);
digitalWrite(relayPin, LOW);
}
void loop() {
digitalWrite(relayPin, HIGH);
delay(5000);
digitalWrite(relayPin, LOW);
delay(5000);
}
Example Arduino Code (Low Level Trigger)
const int relayPin = 7;
void setup() {
pinMode(relayPin, OUTPUT);
digitalWrite(relayPin, HIGH);
}
void loop() {
digitalWrite(relayPin, LOW);
delay(5000);
digitalWrite(relayPin, HIGH);
delay(5000);
}
Example ESP32 / ESP8266 Code (High Level Trigger)
ESP32 operates at 3.3V logic, which is sufficient to activate the relay in High Level Trigger mode .
from machine import Pin
import time
relay = Pin(7, Pin.OUT)
relay.value(0)
while True:
relay.value(1)
time.sleep(5)
relay.value(0)
time.sleep(5)
Important Considerations
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Power Supply: The module requires a stable 24V DC supply capable of providing at least 200mA. The relay coil draws up to 190mA when active .
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Dual Optocoupler Isolation: The dual optocouplers provide enhanced protection against electrical noise and voltage spikes, making this module ideal for industrial environments .
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30A High-Current Capacity: The 30A rating allows switching of heavy industrial loads, but ensure your wiring is appropriately gauged (minimum 10 AWG for 30A continuous) .
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Inductive Loads: For high-power inductive loads (large motors, compressors), adding an external flyback diode across the load terminals is recommended to protect the relay contacts.
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Fault-Tolerant Design: Even if the control line is disconnected, the relay will not operate, ensuring fail-safe behavior .
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JD-VCC Jumper: For applications requiring complete isolation (separate power for relay coil), remove the jumper between DC+ and JD+ and supply 24V to JD+ and JD- independently
Q: What is the difference between High-Level and Low-Level trigger?
High-Level trigger (Active HIGH) activates the relay when the control pin receives a positive voltage (3.3V–24V). Low-Level trigger (Active LOW) activates the relay when the control pin is connected to Ground (0V). The onboard jumper lets you select which mode fits your system
Q: What is the advantage of dual optocoupler isolation?
Dual optocouplers provide enhanced electrical isolation between the control circuit and the high-voltage load. One optocoupler isolates the control signal, while the second isolates the relay coil drive circuit, offering superior protection against electrical noise, back-EMF spikes, and ground loops
Q: What is the maximum load this relay can handle?
The relay contacts are rated for 30A at 250V AC or 30A at 30V DC . For inductive loads like large motors or compressors, it is recommended to derate to 20A–25A to account for startup surges.
Q: Can I control this 24V relay module with a 5V Arduino or 3.3V ESP32?
Yes. The module accepts control signals from 3.3V to 24V . For High Level Trigger mode, a 3.3V HIGH signal is sufficient to activate the relay. For Low Level Trigger mode, a LOW signal (0V) works regardless of the logic voltage.
Q: What is the 30A rating? Is that the maximum for both AC and DC?
Yes, the contacts are rated for 30A at 250V AC and 30A at 30V DC . This high current capacity makes this module suitable for industrial motors, compressors, and heavy-duty equipment.
Q: What power supply do I need for this module?
The module requires a stable 24V DC power supply capable of providing at least 200mA. The relay coil draws up to 190mA when active, plus a small quiescent current of about 5mA
Q: Does the module include a flyback diode?
Yes. The module includes a built-in flyback diode across the relay coil to protect the driving circuit from voltage spikes when the relay de-energizes . This protects your microcontroller from back-EMF.
Q: The relay clicks but my load doesn't turn on. What's wrong?
This indicates the relay is activating but the load circuit is incomplete. Check:
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The load is correctly wired between COM and NO (or COM and NC)
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The load’s neutral/ground is connected correctly
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The load itself is functional
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The load’s current does not exceed the relay’s 30A rating
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Wiring gauge is sufficient for the load current (10 AWG minimum for 30A)
Q: What is the expected lifespan of this relay?
The relay is rated for approximately 100,000 electrical operations at rated load . Actual lifespan depends on switching frequency and load type. For applications requiring very frequent switching, consider using a solid-state relay (SSR).
Q: Can I use this relay for 220V AC applications?
Yes. The contacts are rated for 250V AC, which is suitable for 220V/240V systems. Ensure proper insulation and clearance between the control and load sides for safety .
Q: What is the JD-VCC jumper for?
The JD-VCC jumper allows you to separate the relay coil power from the control logic power. For normal operation, the jumper shorts DC+ to JD+, so both share the 24V supply. For full isolation, remove the jumper and supply 24V separately to JD+ and JD- .
Q: The module's status LED lights up but the relay doesn't click. What's wrong?
The LED indicates the control signal is reaching the optocoupler. If the relay doesn’t click, check:
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The VCC power supply is stable at 24V
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The power supply can provide enough current (at least 200mA)
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The jumper is set correctly for your trigger mode
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The JD-VCC jumper is properly connected
Q: Can I use multiple relay modules with a single PLC or microcontroller?
Yes. Connect each module’s DC+ and DC- in parallel to the same 24V supply (ensure the supply can handle the total current), and connect each IN pin to a separate output on your controller.
Q: What can I build with this 30A 24V relay module?
Popular applications include:
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Industrial control: PLC output expansion, heavy motor control, conveyor systems
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Building automation: HVAC system control, large fan control, compressor switching
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Heavy equipment: Industrial pumps, compressors, manufacturing equipment
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Solar power systems: High-current battery switching, panel control
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Electric vehicles: DC motor control, battery management
Q: Is this module suitable for controlling a large industrial motor?
Yes, with proper consideration. The 30A rating at 250V AC can handle many industrial motors. Ensure the motor’s full-load current does not exceed 30A, and account for startup inrush current which can be 3-6 times higher than running current. Consider using a motor contactor for very large motors.
Q: Can I use this module without a microcontroller?
Yes. You can trigger the relay by manually connecting the IN pin to VCC (High Trigger mode) or GND (Low Trigger mode). This can be done with a simple push button or toggle switch.
Q: What wire gauge should I use for 30A connections?
For 30A continuous current, use 10 AWG or thicker copper wire for the load connections. Ensure all terminals are securely tightened to prevent overheating
