Item specifics
Description
1-Channel Optocoupler Isolation Module Product Overview
This 1‑channel optocoupler isolation module is designed around the high‑quality EL817 photoelectric coupler, featuring 5.0mm pitch screw terminals for easy and reliable wiring. It is ideal for isolating microcontroller output signals when driving inductive loads such as motors and solenoids, and for level matching between different voltage systems (e.g., converting 3.3V/5V MCU signals to 12V/24V PLC inputs). The module offers selectable input voltages of 3‑5V, 12V, or 24V, and a wide output voltage range of 1.8V‑24V. With an isolation voltage of over 3000V, it is widely used in industrial control, PLC interfaces, solenoid valve drivers, motor isolation, inverters, high‑voltage detection, and current amplification.
1-Channel Optocoupler Isolation Module Core Features
High‑Quality EL817 Optocoupler： Genuine EL817, isolation voltage >3000V, input current up to 50mA, output current up to 50mA, operating temperature -55℃ to +110℃ for high reliability and long life
Selectable Input Voltage Options： Available in 3‑5V, 12V, or 24V input versions to match different MCU or controller output levels
Wide Output Voltage Range： Output side supports DC 1.8V‑24V to drive relays, solenoids, PLC inputs, indicators, etc.
5.0mm Pitch Screw Terminals： Solderless screw terminals for secure and convenient wiring, ideal for field installation and maintenance
DIN Rail Mountable： Module can be snapped onto standard DIN rails or screw‑mounted for integration into control cabinets and automation equipment
Signal Frequency Response： Maximum signal frequency 5kHz, suitable for general switching signal isolation and low‑speed pulse transmission
Multiple Functions： Level shifting, isolation drive, inverting output, high‑voltage detection, current amplification, and interference protection
Excellent Noise Immunity： Optocoupler electrically isolates input from output, preventing back EMF and electromagnetic interference from inductive loads from damaging sensitive MCU circuits
1-Channel Optocoupler Isolation Module Applications
Isolation between MCU and Inductive Loads： Protects MCU I/Os from voltage spikes and interference generated by motors, solenoids, relays, etc.
PLC Input Level Matching： Converts 3.3V/5V MCU outputs to 24V PLC inputs for seamless integration
Inverter Function： Inverts the input signal, suitable for logic negation applications
High‑Voltage Detection Isolation： Safely detects 12V or 24V sensor signals with a 5V MCU via isolation
Current Amplification： Amplifies weak MCU output current to drive loads that require higher current
Industrial Automation： Signal isolation between PLCs and peripheral devices to improve system reliability
1-Channel Optocoupler Isolation Module Key Advantages
One Module, Multiple Solutions： Combines level shifting, isolation, inversion, voltage detection, and current amplification in a single module to solve various signal matching and isolation problems
Three Input Versions to Match Mainstream Systems： Choose 3‑5V, 12V, or 24V input to work with Arduino, STM32, 8051 (3.3V/5V), as well as PLCs and industrial controllers (12V/24V)
3000V High Isolation Protects Critical Equipment： Effectively blocks electrical connection between input and output, preventing high voltage, surges, and back EMF from damaging MCUs or PLCs – especially valuable for driving motors and solenoids
Screw Terminals + DIN Rail Mount – Industrial Installation： 5.0mm pitch screw terminals are robust and easy to wire; the module snaps onto standard DIN rails or screws into place for control cabinets
Wide Operating Temperature & Long Life： EL817 operates from -55℃ to +110℃ for harsh environments; solid‑state optocoupler has no mechanical contacts, offering far longer life than mechanical relays
Good Drive Capability & Flexibility： Output up to 50mA can directly drive small relays, LEDs, PLC input modules; input works with as little as 1mA
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FAQ:
What is the 1‑channel EL817 optocoupler isolation module and what is it used for?
It is a DIN‑rail‑mountable signal isolator built around the popular EL817 photoelectric coupler. It accepts a DC control voltage on the input side and switches an electrically isolated open‑collector output on the other side. This protects microcontrollers, PLCs, and sensitive logic circuits from high‑voltage transients, ground loops, and noise. The module is widely used for interfacing between different voltage domains, isolating sensor signals, driving relays, and converting levels in industrial automation.
What input voltage versions are available for this EL817 module? How do I choose the right one?
Modules are typically offered with a fixed input voltage option: 3‑5 V, 12 V, or 24 V DC. The version determines the built‑in series resistor that limits the current through the internal LED. A 3‑5 V module works directly with 3.3 V and 5 V microcontrollers (Arduino, ESP32). The 12 V variant is suitable for automotive and industrial control signals, while the 24 V version interfaces directly with PLC digital outputs. Always pick the module whose nominal voltage matches your driving signal, and never apply 24 V to a 3‑5 V version, or the LED may be destroyed.
How do I wire the EL817 optocoupler module? What are the input and output connections?
Input side (control signal): connect the positive wire to “IN+” and the negative wire to “IN‑”. The module is polarity‑sensitive—the internal LED illuminates when current flows from IN+ to IN‑. Output side (isolated switch): you have three terminals—usually marked “COM”, “NO”, and “NC” (depending on the board) or simply “C” (collector) and “E” (emitter). The output is a photo‑transistor without an internal pull‑up; you must provide an external supply (e.g., 3.3‑24 V) and a load or pull‑up resistor to obtain a logic‑level signal. A typical 10 kΩ pull‑up to the output‑side VCC is sufficient for most MCU inputs.
What is the maximum isolation voltage of this module? Is it safe for industrial use?
The EL817 optical coupler itself is rated for a minimum isolation voltage of 5,000 Vrms between input and output. The PCB layout includes a physical cut‑out or creepage slot that further improves the clearance distance. This isolation level is suitable for most industrial applications—including machine control panels and motor drives—where low‑voltage logic must be protected from field‑side transients. However, for mains‑connected circuits or safety‑critical isolation, always consult the module’s datasheet and verify that the clearance meets your local safety standards.
Can the output transistor drive a relay or a small load directly? What is the maximum output current?
The EL817 photo‑transistor is not designed to switch heavy loads. Its maximum collector current is typically 50 mA, and the saturation voltage is around 0.3‑0.5 V at 20 mA. You can use it to directly drive a small LED, a low‑current SSR, or the coil of a reed relay, but for standard mechanical relays (which often draw 70‑100 mA), you should use the module’s output to drive an external transistor or MOSFET. Exceeding the current rating will permanently damage the photo‑transistor.
What is the response time of the EL817 module? Can it handle high‑speed pulse signals?
The EL817 has a typical rise time of 2 µs and a fall time of 3 µs, giving a maximum practical frequency of around 80‑100 kHz for clean square‑wave signals. For standard serial communication (UART at 115200 baud) or moderate‑speed PWM, the EL817 works reliably. However, for very fast digital protocols (SPI at MHz speeds) or precision timing applications, you should choose a high‑speed digital isolator (e.g., ISO7741) instead, as the EL817’s propagation delay and pulse‑width distortion can become significant above a few hundred kHz.
How do I interface this module with an Arduino or Raspberry Pi? What pull‑up resistor value should I use?
Connect the output transistor’s collector to the MCU’s digital input pin, and the emitter to the MCU’s GND. Add a pull‑up resistor (4.7‑10 kΩ) from the collector to the MCU’s VCC (3.3 V or 5 V). When the input LED is off, the transistor is non‑conducting and the pull‑up holds the pin HIGH. When the LED is on, the transistor saturates and pulls the pin LOW. Configure the MCU pin as `INPUT` and read the logic level directly—no additional library is needed.
Can I use this module to convert a 24 V PLC signal to a 3.3 V MCU input?
Yes, this is a primary use case. Select the 24 V input version of the module, connect the PLC’s 24 V digital output to IN+ and 0 V to IN‑. On the output side, connect the transistor’s collector to the 3.3 V MCU input with a 10 kΩ pull‑up to 3.3 V, and the emitter to the MCU’s GND. The module provides full galvanic isolation between the 24 V and 3.3 V domains, protecting the low‑voltage side from surges and wiring faults.
Does the module require an external power supply? What do the indicator LEDs show?
The input side is powered directly by the control signal—no external supply is needed. The output side needs an external voltage source and a pull‑up resistor to generate a logic level. Many DIN‑rail modules include a green input LED that lights up when current flows through the input, and an optional red output LED that indicates the transistor state. These LEDs are purely for visual diagnostics and do not affect the isolation performance.
What are the most common applications for this EL817 optocoupler module in industrial automation?
It is used for PLC input isolation (converting 24 V field signals to 5 V/3.3 V logic), driving small relays or SSRs from a microcontroller, eliminating ground loops in sensor networks, protecting MCU pins from voltage spikes, and as a basic pulse‑width modulator for motor speed control. Its compact DIN‑rail form factor makes it easy to integrate into control cabinets alongside other automation components.