LTH-209-01 Reflective Photoelectric Interrupter Datasheet - Reflective Object Sensor - Chinese Technical Documentation

1. Product Overview

LTH-209-01 is a reflective photoelectric interrupter module specifically designed for non-contact switch applications. This optoelectronic device integrates an infrared emitting diode and a phototransistor within a compact package. Its primary function is to detect the presence of a reflective object within its sensing gap. The module is designed for direct mounting on a printed circuit board or for use with a dual in-line package socket, providing flexibility for system integration. Its core advantages include non-contact operation (eliminating mechanical wear and ensuring long-term reliability) and fast switching speed suitable for various sensing and counting tasks. Target markets include automation equipment, consumer electronics, security systems, and industrial control fields requiring precise and reliable object detection.

2. In-depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. Key parameters include:

• Infrared Diode Continuous Forward Current (I_F):Maximum 50 mA. This defines the upper limit of DC current that can continuously pass through the infrared LED.
• Infrared diode reverse voltage (V_R):Maximum 5 V. Exceeding this reverse bias voltage may damage the LED junction.
• Phototransistor collector current (I_C):Maximum 20 mA. This is the maximum continuous current the output transistor can sink.
• Phototransistor collector-emitter voltage (V_CEO):Maximum 30 V. This is the maximum voltage that can be applied between the phototransistor's collector and emitter pins.
• Operating temperature range:-35°C to +65°C. Ensure the device operates within specifications across this ambient temperature range.
• Pin soldering temperature:260°C for 5 seconds at 1.6mm from the case. This is critical for wave soldering or reflow processes.

Power derating description:For ambient temperatures above 25°C, the maximum power dissipation for the infrared diode (75 mW) and phototransistor (100 mW) must be linearly derated at a rate of 1.33 mW/°C. This is critical for thermal management and long-term reliability.

2.2 Electrical and Optical Characteristics

These parameters are specified at an ambient temperature (T_A) is specified at 25°C, defining the typical performance of the device.

2.2.1 Input Infrared Diode Characteristics

• Forward Voltage (V_F):At Forward Current (I_FWhen the forward current is 20 mA, the typical forward voltage is 1.2V to 1.6V. This parameter is crucial for designing the current-limiting drive circuit for LEDs.
• Reverse Current (I_R):When the Reverse Voltage (V_R) is 5V, the maximum reverse current is 100 µA. A low reverse current indicates good junction quality.

2.2.2 Output Phototransistor Characteristics

• Collector-Emitter Breakdown Voltage (V_(BR)CEO):At I_CWhen =1mA, minimum 30V. This high breakdown voltage allows the use of higher pull-up voltages in the output circuit.
• Collector-emitter dark current (I_CEO):At V_CEWhen =10V, maximum 100 nA. This is the leakage current when the infrared diode is off (no light). Low dark current is crucial for achieving a good signal-to-noise ratio, especially in low-light or high-gain applications.

2.2.3 Coupler (System) Characteristics

These parameters describe the performance of the complete sensor system (infrared LED + phototransistor).

• Collector-Emitter saturation voltage (V_CE(SAT)):At I_C=0.08mA and I_F=20mA, maximum 0.4V. This low saturation voltage indicates that the phototransistor can function as an efficient switch, pulling the output close to ground level when activated.
• Collector current in the on state (I_C(ON)):At V_CE=5V and I_F=20mA, minimum 0.16 mA.Test Conditions:This key parameter is measured by placing a standard reflective surface (90% diffuse white paper) at a distance of 3.81 mm (0.15 inches) from the sensor surface. This standardized distance and surface define the "sensing gap" and "minimum detectable reflectance" for the device's specified performance.

3. Mechanical and Packaging Information

3.1 Package Dimensions

LTH-209-01 uses a standard 4-pin DIP (Dual In-line Package) housing. Unless otherwise specified on the dimension drawing, all dimensions are in millimeters with a default tolerance of ±0.25mm. This package is designed for through-hole PCB mounting. An accurate dimension drawing (including body length, width, height, pin pitch, and pin diameter) is crucial for PCB pad design and mechanical integration into the final product enclosure.

3.2 Pin Arrangement and Polarity Identification

The device has four pins. Typically, two pins are for the anode and cathode of the infrared emitting diode, and the other two are for the collector and emitter of the NPN phototransistor. Correct identification is crucial to prevent damage. The pin arrangement diagram in the datasheet must be consulted. The package usually includes a notch, dot, or bevel to indicate pin 1. The infrared diode is polarity-sensitive, and the collector and emitter of the phototransistor must be correctly connected for proper switching operation.

4. Welding and Assembly Guide

Manual Soldering:Use a temperature-controlled soldering iron. The absolute maximum ratings specify that pins can withstand 260°C for 5 seconds when measured 1.6mm from the plastic package. It is recommended to use the lowest possible temperature and the shortest time to form a reliable solder joint to minimize thermal stress on internal components and the plastic package.

Wave Soldering:Yana yiwu, amma dole ne a bi daidai da tsarin zafin jiki/lokaci (1.6mm daga harsashi, 260°C na tsawon dakika 5). Ana ba da shawarar yin dumama kafin a yi amfani da shi don rage tasirin zafi.

Tsaftacewa:Idan ana bukatar tsaftacewa bayan walda, yi amfani da hanyoyi da kaushi masu jituwa da kayan filastik na na'urar don guje wa fashewar taga na gani ko duhu.

Yanayin ajiya:Store in an environment within the specified storage temperature range of -40°C to +100°C. It is recommended to keep the device in its original moisture barrier bag until use to prevent contamination of the optical surfaces.

5. Application Recommendations

5.1 Typical Application Circuit

The most common circuit configuration uses the LTH-209-01 as a digital switch. The infrared diode is driven by a constant current source or a current-limiting resistor from a voltage source (e.g., 5V). According to the test conditions, an I of 20mA is typically used._FThe phototransistor is connected in a common-emitter configuration: the collector is connected through a pull-up resistor (R_CC) Connect to the supply voltage (V_L, up to 30V), emitter to ground. The output signal is taken from the collector node. When no reflective object is present, the phototransistor is off (high output). When a reflective object enters the sensing gap, infrared light reflects onto the phototransistor, turning it on and pulling the output low.

5.2 Design Considerations and Best Practices

• Selecting the pull-up resistor (R_L):R_LThe value of R determines the output current and voltage swing. It must be selected based on the required I_C(ON)and the input characteristics of the load (e.g., a microcontroller's GPIO). A smaller R_Lprovides faster switching speed and better noise immunity, but with higher power consumption. Ensure that I_Cdoes not exceed 20mA: R_L> (V_CC- V_CE(SAT)) / 20mA.
• Minimize Electrical Noise:Place a bypass capacitor (e.g., 0.1µF) near the device's power supply pins. Keep signal traces (especially the phototransistor output line) short to reduce susceptibility to electromagnetic interference.
• Optical Considerations:Inductive performance depends on the target object's reflectivity, color, and distance. The specified I_C(ON)is for a white surface with 90% reflectivity at 3.81mm. Objects with darker colors or at greater distances will produce a smaller output signal. For consistent operation, design the system's detection threshold accordingly (e.g., the comparator's reference voltage). Avoid direct exposure of the sensor's aperture to ambient light sources (especially sunlight or incandescent lamps rich in infrared), as this may cause false triggering. In high ambient light environments, modulated infrared signals and synchronous detection can be used.
• Mechanical alignment:Ensure the target object's path is consistent and passes within the optimal sensing gap (approximately near the specified 3.81mm) for reliable detection.

6. Technical Comparison and Differentiation

LTH-209-01, as a reflective photoelectric interrupter, differs from other types of photoelectric sensors:

• Comparison with transmissive photoelectric interrupters (slot-type optocouplers):Transmissive types have a physical gap between the emitter and detector; an object is detected when it blocks the light path. Reflective types like the LTH-209-01 detect objects when they reflect light back. Reflective sensors are often simpler to install as they only require access from one side, but their performance is more dependent on the object's surface characteristics.
• Compared to photoelectric logic sensors:Some photointerrupters have built-in logic circuits (Schmitt triggers, amplifiers) to provide clean digital outputs. The LTH-209-01 provides a simple analog phototransistor output, offering greater flexibility but requiring external circuitry (e.g., a comparator) to generate robust digital signals in noisy environments.
• Key advantages of this model:The combination of a relatively high collector-emitter breakdown voltage (30V), low saturation voltage, and standardized sensitivity test conditions provides a good balance for general-purpose reflective sensing applications.

7. Frequently Asked Questions

Q1: What is the optimal distance for detecting an object?
A1: The datasheet specifies the collector current (I_C(ON)) with the target at 3.81mm (0.15 inches). This is the standardized test distance. The actual optimal distance depends on the target's reflectivity. For highly reflective targets, detection may be effective at a slightly greater distance. For reliable design, use 3.81mm as the nominal operating point.

Q2: Ina iya amfani da tushen wutar lantarki kai tsaye don kunna LED infrared?
A2: A'a. LED infrared kamar kowane diode, dole ne a kunna shi da ƙarfin lantarki. Haɗa shi kai tsaye zuwa tushen wutar lantarki zai haifar da ƙarfin lantarki mai yawa, wanda zai iya lalata kayan aikin. Lallai yi amfani da resistor mai iyakancewa a jere. Tsarin lissafin ƙimar resistor shine R = (V_{Power supply}- V_F) / I_F. For a 5V power supply, V_F=1.4V, I_F=20mA: R = (5 - 1.4) / 0.02 = 180 ohms.

Q3: Why is my output signal unstable or noisy?
A3: Common causes include: 1) Insufficient pull-up resistor value leading to slow rise time, 2) Electrical noise pickup on long output traces (use bypass capacitors and shorten traces), 3) Ambient infrared light interference (shield the sensor or use modulation), 4) Variations in target object reflectivity or inconsistent distance.

Q4: What does the specification "Linear derating 1.33 mW/°C" mean?
A4: Wannan doka ce ta rage zafi. Matsakaicin ikon da aka yarda (75 mW don diode, 100 mW don transistor) an ƙayyade shi a 25°C. Ga kowane digiri 1 na hawan yanayin zafi (sama da 25°C), dole ne ku rage matsakaicin ikon da aka yarda da 1.33 mW. Misali, a 65°C (digiri 40 sama da 25°C), matsakaicin ikon transistor bayan ragewa shine 100 mW - (40 * 1.33 mW) = 100 - 53.2 = 46.8 mW.

8. Case Studies of Practical Applications

Yanayi: Gano takarda a cikin firinta.
LTH-209-01 inaweza kutumika kugundua ukingo wa mbele wa karatasi inapoingia kwenye utaratibu wa kuchapisha. Sensor imewekwa kwenye bodi kuu, na uso wake wa kuhisi ukiwa unaelekea kwenye njia ya karatasi. Ukanda unaoakisi au karatasi yenyewe (ikiwa uakisi wake unatosha) hutumika kama lengo. Wakati hakuna karatasi, pato ni ya juu. Wakati ukingo wa karatasi unapopita chini ya sensor, mwanga wa infrared unaoakisiwa huamsha transistor ya fotoelektrini, na kuvuta pato chini. Ishara hii ya dijiti inamjulisha kudhibiti kichapishi mahali pa karatasi, na kuwezesha udhibiti sahihi wa wakati wa kuchapisha. Mambo muhimu ya muundo hapa ni pamoja na: kuchagua upinzani wa kuvuta juu ili kuunganisha kwa usahihi na mantiki ya 3.3V au 5V ya MCU; kuhakikisha njia ya karatasi imeimarika kimakanika ili kudumisha pengo sahihi la kuhisi; na uwezekano wa kuongeza kichujio rahisi cha RC kwenye pato ili kuondoa mtetemo wa ishara unaosababishwa na muundo wa karatasi.

9. Working Principle

LTH-209-01 inafanya kazi kulingana na kanuni ya kuakisi mwanga uliobadilishwa na ubadilishaji wa fotoelektrini. Ndani, diode inayotoa mwanga wa infrared hutoa mwanga wenye urefu wa wimbi kawaida karibu 940nm, ambao hauwezi kuonekana na jicho la binadamu. Mwanga huu hutoka mbele ya kifaa. Wakati kitu chenye uakisi unaofaa kinaingia kwenye uwanja wa maono na kuwepo kwenye masafa yanayofaa, sehemu ya mionzi ya infrared inayotolewa huakisiwa kutoka kwenye uso wa kitu na kurudi kwenye kifaa. Transistor ya fotoelektrini ya aina ya NPN ya silikoni, iliyowekwa karibu na LED ya infrared ndani ya kifaa kimoja, hupokea mwanga huu unaoakisiwa. Fotoni zinazoangukia eneo la msingi la transistor ya fotoelektrini huzalisha jozi za elektroni na mashimo, na kwa ufanisi kuzalisha mkondo wa msingi. Mkondo huu wa msingi unaozalishwa na mwanga huongezwa kwa faida ya transistor, na hivyo kuzalisha mkondo mkubwa wa kolekta unaoweza kupimwa nje. Mabadiliko haya ya mkondo wa kolekta (kutoka kwa mkondo wa giza mdogo sana hadi I_C(ON)) ndiyo utaratibu wa msingi wa kugundua. Kwa hivyo, kifaa hiki hubadilisha tukio la macho (uwepo wa kitu kinachoakisi) kuwa ishara ya umeme.

10. Industry Trends and Background

Reflective photoelectric interrupters like the LTH-209-01 represent a mature and reliable technology within the broader photoelectric sensor market. General trends in this field include miniaturization, increased integration, and enhanced functionality. Newer devices may adopt surface-mount packages to accommodate automated assembly, feature lower power consumption, and incorporate signal conditioning ICs that provide digital or analog outputs. Furthermore, there is a trend toward using specific wavelengths or incorporating optical filters to improve immunity to ambient light. Concurrently, advancements in materials and packaging technologies continue to enhance the temperature range, moisture resistance, and long-term stability of these components. Despite the availability of more advanced alternatives, through-hole, discrete phototransistor-output reflective sensors remain a cost-effective and versatile solution for countless non-contact detection applications, particularly where simplicity, robustness, and proven performance are paramount.