Technical Explanation for Photomicrosensors CSM_Photomicro_TG_E_4_2 Introduction Sensors What Is a Photomicrosensor? Switches A Photomicrosensor is a small photoelectronic sensor with an amplifier built into it that is used primarily as a component for building into equipment. Like any ordinary photoelectric sensor with a built-in amplifier, it is used, for example, in applications to detect passing objects or in positioning applications. The sensing object is most often a piece of metal called a "dog". When the dog enters the sensing area, it is optically detected by the Photomicrosensor, which outputs a signal. Features Relays 5. Other Specifications: Degree of Protection and Output Current A waterproof structure is not required because it is assumed the Photomicrosensors will be built into other equipment, and the output current rating can be kept low. Also, most models can operate on a 5-VDC power supply. Control Components Automation Systems 3. Downsizing Is Possible with the Sensing Distances Required for Building into Equipment The standard sensing distances (slot width) are specifically intended to be used for building into equipment. Slot-type Sensors, for example, have a 3.6 mm or 5 mm sensing distance. Diffuse-reflective and Limited Reflective Sensors have a sensing distance of less than 5 mm, and Retroreflective and Through-beam Sensors, less than 1 m. Safety Components Photomicrosensors have the following advantages over ordinary photoelectric sensors with built-in amplifiers 4. Indicator Lighting Mode 1. Many Different Shapes in One Model Series The indicator on many Photomicrosensors lights when light The EE-SX67 Series, for example, has models with eight is incident. Some Photomicrosensors have specific models different slot configurations, allowing the customer to on which the indicator lights when light is interrupted. When choose the best configuration for the installation position. lighting the indicator for position adjustment applications of 2. Low Price Slot-type Sensors, for example, it may be more convenient Ratings and performances are limited to those required for to use a model that lights the indicator when light is building into equipment, and the required IP degree of interrupted. When using the indicator to check the power protection is easier to achieve, making prices very supply status, on the other hand, it may be convenient to reasonable. use a model that lights the indicator when light is incident. Operating Principles (Glass) Refractive index: 1.5 (Air) Refractive index: 1 (Mirror) Regular Reflection (Mirror) Retroreflection (Paper) Others Refractive index: 1 Power Supplies / In Addition (Air) Energy Conservation Support / Environment Measure Equipment Refraction Refraction is the phenomenon of light being deflected as it passes obliquely through the boundary between two media with different refractive indices. Reflection (Regular Reflection, Retroreflection, and Diffuse Reflection) A flat surface, such as glass or a mirror, reflects light at an angle equal to the incident angle of the light. This kind of reflection is called regular reflection. Retroreflectors (also called a corner cube) take advantage of this principle by arranging three flat surfaces perpendicular to each other. "Retro" means "to return toward the source." The light reflected off the reflectors travels back towards the emitter, thus the term "retroreflective". Matte surfaces, such as white paper, reflect light in all directions. This scattering of light is called diffuse reflection. This principle is the sensing method used by Diffuse-reflective Sensors. Motion / Drives 1. Properties of Light Rectilinear Propagation When light travels through air or water, it always travels in a straight line. The slit on the outside of a Through-beam Sensor that is used to detect small objects is an example of how this principle is applied to practical use. Diffuse Reflection Common 1 Technical Explanation for Photomicrosensors Sensors 2. Light Sources Light Generation Non-modulated Light Non-modulated light facilitates high-speed response by continuously radiating a constant amount of light. There is the drawback, however, of susceptibility to external light interference. Modulated Light Modulated light is not affected by sunlight, light from incandescent bulbs, and other external light interference. An LED emitter is pulse-lighted, and the received signal is processed to remove the DC component. Light intensity Cycle Safety Components 0 Switches Light intensity 0 Time Time Light from LED Relays Light incident Control Components Sunlight/ Incandescent Light Light interrupted Automation Systems Input to Sensor's Receiver DC Component Removal of DC Component Motion / Drives After DC Component Removal at Receiver Digitization Energy Conservation Support / Environment Measure Equipment ON Sensor Output (Light-ON) OFF Power Supplies / In Addition Others Common 2 Technical Explanation for Photomicrosensors Classification 2. Considerations when Choosing a Sensing Method (1) Slot Sensors • Shape, slot width, connection (pre-wired/connector) • Presence or absence of external light interference (nonmodulated light/modulated light) • Output configuration (Light-ON/Dark-ON, NPN/PNP) • Indicator (Light-ON/Dark-ON) (2) Through-beam Sensors • Shape, sensing distance • Output configuration (Light-ON/Dark-ON) (3) Retroreflective Sensors • Sensing distance • Output configuration (Light-ON/Dark-ON) (4) Diffusive/Limited-reflective Sensors • Shape, sensing distance • Presence or absence of background objects (Diffusereflective/Limited-reflective Sensors) • External light interference (non-modulated light/ modulated light) • Output configuration (Light-ON/Dark-ON) Switches Safety Components Relays Control Components Automation Systems (1) Slot Sensors Slot Sensors are suitable for applications using a thin sensing object, or "dog," that require a highly precise sensing position. Setup is easy because no optical axis adjustment is needed. There are many product variations. The necessary configuration, connection method, and other items can be selected from a wide array of models. (2) Through-beam Sensors Through-beam Sensors are suitable for applications that require relatively long sensing distances. (3) Retroreflective Sensors Retroreflective Sensors are suitable for applications that require relatively long sensing distances. They have the advantage of requiring less work for wiring and optical axis adjustment when compared to Through-beam Sensors. (4) Diffuse-reflective Sensors Diffuse-reflective Sensors are suitable for applications where the sensing object is thick and won't fit into the slot of a Slot Sensor. (5) Limited-reflective Sensors Limited-reflective Sensors are basically the same as Diffuse-reflective Sensors, but they are suitable when background objects are present. (With Diffuse-reflective Sensors, the presence of a background object with a higher reflectivity than the sensing object (e.g., metals with mirror finishing) may cause sensing instability.) Sensors 1. Classification by Sensing Method For information on the configuration of each method, refer to the sensing distance reference diagram in Explanation of Terms. Motion / Drives Energy Conservation Support / Environment Measure Equipment Power Supplies / In Addition Others Common 3 Technical Explanation for Photomicrosensors Explanation of Terms Term Reference diagram Non-modulated light Modulated light Explanation Modulated light Light intensity Light intensity Modulated light: Method used to detect light emitted in pulses by the emitter element. 0 Time Slot width Time Sensing distance Emitter The slot width, i.e., the distance between the opposing faces of the emitter and receiver, is the sensing distance. Receiver Safety Components Through-beam Sensors (with slot) Non-modulated light: Method used to detect light steadily emitted by the emitter element. Switches 0 Cycle Sensors Non-modulated light Sensing distance Through-beam Sensors Emitter Receiver Sensing distance Sensing distance Retroreflective Sensors Reflector Sensing distance Sensing object Emitter/receiver The minimum distance that can be set for a standard sensing object (white paper) considering factors such as the variation between products and fluctuations in temperature. Note: The actual value under standard conditions for each method is longer than the rated sensing distance. Automation Systems Diffusereflective Sensors Limitedreflective Sensors Control Components Emitter/receiver Relays The minimum distance that can be set considering factors such as the variation between products and fluctuations in temperature. Note: The actual value under standard conditions for each method is longer than the rated sensing distance. Releases Operates Operates Sensing object Operates Releases The difference in distance between the operating point and releasing point. Motion / Drives Differential distance Releases Through-beam Differential distance Reflective Energy Conservation Support / Environment Measure Equipment (Example for Slot Sensor) Disk The frequency at which an object satisfying specified conditions (size, transparency rate, reflection factor, sensing distance, and power supply voltage) can be repeatedly detected. Response frequency 1 mm 2.1 mm 1 mm t = 0.2 mm Power Supplies / In Addition (t: thickness) 0 Response time 0 Light input t Control output t White paper Others Operating time (TON) The delay from the light input turning ON/OFF until the control output operation or release operation. The following equation generally applies. Operating time (Ton) ≈ Releasing time (Toff) Releasing time (TOFF) White paper White paper The level of illumination on the sensing surface that enables stable operation of the Sensor. Receiver Receiver Common Ambient illumination Receiver 4 Technical Explanation for Photomicrosensors Further Information Sensing Position Characteristics Sensors Interpreting Engineering Data Repeated Sensing Position Characteristics Sample characteristics for the EE-SX77 Sample characteristics for the EE-SX77 Switches Dark-ON Dark-ON d = ±0.002 mm Light-ON 0 1.0 2.0 3.0 4.0 5.0 Light-ON 2.16 6.0 2.18 2.20 2.22 Distance d (mm) Distance d (mm) Vcc = 24V Number of repetitions: 20, Ta = 25°C Receiver Output Excess Gain vs. Sensing Distance Characteristics Parallel Movement Characteristics Sample characteristics for the EE-SPW311/411 Sample characteristics for the EE-SPW311/411 Distance Y (mm) 1,000 500 300 100 50 30 Control Components • Indicates the discrepancy in the edge position of the sensing object when the Sensor responds. It serves as a guide for the positioning accuracy of the sensing object. Relays • Indicates whether or not the Sensor responds with respect to sensing object edge position. (Design the application so that light will be completely interrupted.) 140 120 100 80 Automation Systems Receiver output excess gain (multiple) Safety Components d d 10 60 5 3 Distance Y 40 1 20 Distance X 0 0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Distance X (m) • Through-beam Sensors: Indicates the receiver's sensing limit position when the emitter position is fixed. • Retroreflective Sensor: Indicates the sensing limit position of the Retroreflector when the Sensor position is fixed. • When setting up multiple Through-beam Sensors, 1.5 times the area shown is necessary to prevent mutual interference. Operating Range Characteristics Sensing Distance vs. Object Area Characteristics Sensing object: 2 White paper (15 × 15 mm ) (reflection factor: 90%) Releases 6 5 Operates 4 3 Relative sensing distance d (%) 7 Sample characteristics for the EE-SPY 500 Sensing object: 2 White paper (15 × 15 mm ) (reflection factor: 90%) 300 Power Supplies / In Addition Distance Y (mm) Sample characteristics for the EE-SPY311/411 Energy Conservation Support / Environment Measure Equipment • Values shown are for the receiver output excess gain when the sensitivity is set to the maximum value. • The above example is for models with a rated sensing distance of 1 m. The receiver output excess gain can be thought of as being approximately 10 times the rated sensing distance. Motion / Drives 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Distance between Sensors (m) 200 100 80 50 X 2 30 Others Y 1 0 −5 −4 −3 −2 −1 0 1 2 3 4 5 Distance X (mm) 1 2 3 5 10 20 50 100 Size (mm) • Indicates the change in the sensing distance when the area of a white piece of paper with a reflection factor of 90% of the standard sensing object is increased. (The sensing distance will change with the reflection factor.) Common • Indicates the starting sensing position when the standard sensing object is moved perpendicular to the optical axis. (These values apply to the standard sensing object. If the sensing object changes, the operating range and sensing distances also change.) 10 5