## Electronic Overview: E3JK-R4M2-2M The **E3JK-R4M2-2M** is a popular industrial long-distance photoelectric sensor manufactured by Omron. It is a **Retro-reflective** type sensor, meaning it emits a beam of light that must bounce off a reflector and return to the sensor head to detect an object. --- ### 1. Key Technical Specifications The following table summarizes the primary electronic and operational characteristics of the device: | Feature | Specification | | :--- | :--- | | **Sensing Method** | Retro-reflective (with Polarizing Filter) | | **Sensing Distance** | 0.1 to 4 meters (when using E39-R1 reflector) | | **Supply Voltage** | 24 to 240 VAC / 24 to 240 VDC (Universal) | | **Output Type** | Relay Output (SPDT) | | **Contact Capacity** | 3A at 250 VAC (Resistive Load) | | **Power Consumption** | 3W Max | | **Response Time** | 20 ms Max | | **Light Source** | Red LED (624 nm) | --- ### 2. Electronic Component Breakdown #### A. Universal Power Supply One of the most significant electronic features of this model is its **integrated power supply**. It can accept a wide range of voltages (both AC and DC) without needing a separate transformer or power converter. This makes it highly versatile for various industrial control panels. #### B. Relay Output (SPDT) Unlike NPN/PNP sensors that output a low-current transistor signal, the **R4M2** uses a mechanical **Single Pole Double Throw (SPDT)** relay. * **Terminals:** It provides one Normally Open (NO) and one Normally Closed (NC) contact. * **Advantage:** It can directly switch higher current loads (up to 3A) like small motors, solenoids, or light bulbs. #### C. Polarizing Filter (MSR Function) The sensor includes built-in polarizing filters. * **The Problem:** Shiny objects (like a stainless steel can) can sometimes reflect light back to the sensor, tricking it into thinking no object is there. * **The Electronic Solution:** The MSR (Mirror Surface Rejection) function ensures that only light reflected from the specific corner-cube reflector is received, allowing the sensor to detect even mirror-like objects reliably. --- ### 3. Wiring Configuration The unit typically comes with a 2-meter, 5-core cable. The internal wiring logic is as follows: | Wire Color | Function | Description | | :--- | :--- | :--- | | **Brown** | Power (L1/+) | 24-240V Input | | **Blue** | Power (L2/-) | 24-240V Input | | **White** | Relay Common (COM) | The shared contact for the relay | | **Black** | Relay NO | Closes when light is interrupted (Dark-ON) | | **Gray** | Relay NC | Opens when light is interrupted | --- ### 4. Operation Modes The "M2" designation indicates the output logic: * **Light-ON / Dark-ON Selectable:** Most E3JK models feature a switch inside the housing to toggle whether the relay activates when the beam is broken (Dark-ON) or when the beam is clear (Light-ON).