ITR8307/F43

The ITR8307/F43 is a reflective-type photo interrupter (optical sensor) manufactured by Everlight Electronics, combining a GaAs infrared emitting diode (IR LED) and an NPN silicon phototransistor in a compact 4-pin DIP through-hole package. Both elements are mounted side-by-side on converging optical axes within a black thermoplastic housing that blocks visible light.

The IR LED emits at a peak wavelength of 940 nm with a typical forward voltage of 1.2V at 20 mA. The phototransistor detects infrared radiation reflected from a surface placed within the sensing range of approximately 1 mm. The minimum collector current (Ic_ON) is 0.1 mA at VCE=5V and IF=20mA with a reflective surface at 1 mm distance.

Key specifications include: collector-emitter breakdown voltage (BVCEO) 30V, emitter-collector breakdown voltage (BVECO) 5V, maximum collector current 50 mA, maximum forward current 50 mA, peak forward current 1A (tw=100us, T=10ms), and maximum collector power dissipation 100 mW. The rise and fall times are typically 20 us each at VCE=2V, Ic=10mA, RL=100 ohm.

The device operates over a temperature range of -25C to +85C with storage from -30C to +90C. The dark current (ICEO) is typically less than 1 uA at VCE=10V. The cut-off visible wavelength feature reduces false triggering from ambient light sources.

The 4-DIP package provides through-hole mounting with pins arranged as: Pin 1 = CATHODE (IR LED), Pin 2 = ANODE (IR LED), Pin 3 = COLLECTOR (phototransistor), Pin 4 = EMITTER (phototransistor). The standard packaging is 160 pieces per tube.

Common applications include non-contact object detection, paper sensing in printers and copiers, position sensing in cameras and VCRs, and various microcomputer-controlled equipment. The reflective sensing principle eliminates the need for a separate transmitter-receiver alignment across a slot, making it easier to mount on the same side of a surface.

The ITR8307/F43 operates as a reflective optical sensor, detecting the presence or absence of an object by measuring infrared light reflected from a nearby surface.

Infrared Emission: The GaAs IR LED (pins 1-2) is driven by a forward current (typically 5-20 mA) and emits infrared radiation at a peak wavelength of 940 nm. The LED is forward-biased by connecting the anode (pin 2) to a positive supply through a current-limiting resistor, and the cathode (pin 1) to ground. The emitted IR beam is directed outward from the package at a controlled angle determined by the internal lens geometry.

Reflective Detection: When an object or reflective surface is placed within the sensing distance (approximately 1 mm) in front of the sensor, a portion of the emitted IR light reflects off the surface and enters the phototransistor (pins 3-4). The NPN silicon phototransistor collects this reflected IR radiation and generates a photocurrent proportional to the received light intensity. The phototransistor is connected in a common-emitter configuration: the collector (pin 3) is pulled up to VCC through a load resistor, and the emitter (pin 4) is connected to ground. When IR light is received, the phototransistor conducts, causing the collector voltage to drop (logic LOW). When no object is present or the surface is non-reflective, the phototransistor is off (dark current only), and the collector voltage remains HIGH.

Output Signal: The output is an analog signal from the phototransistor collector. The collector current depends on the reflectivity of the target surface, the distance to the surface, and the LED forward current. For digital applications, a comparator or Schmitt trigger can be added to produce a clean digital output. The typical rise and fall times of 20 us make the device suitable for relatively slow-speed detection applications.

Visible Light Rejection: The black thermoplastic housing and the silicon phototransistor spectral response (peaked near 940 nm) provide inherent rejection of visible light, reducing false triggering from ambient lighting. However, direct exposure to strong sunlight or bright indoor lighting may still cause interference.

Design Considerations: The LED should be driven with a constant current (typically 20 mA) for consistent performance. The load resistor on the collector determines the output voltage swing and the switching speed — lower resistance gives faster switching but lower output voltage swing. A typical application circuit uses VCC=5V, IF=20mA, and RL=10 kohm for the collector load.