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Photosensor- Long Range


The reflectivity of infrared light varies with the color and distance of the reflecting surface, According to this principle,Photosensor- Long Range utilizes a ST178H reflective photosensor module to detect color and distance. When a light-colored object approaches,the signal intensity received by infrared reflective sensor increases and the indicator LED on board turns ON. When a dark-colored object approaches, the intensity decreases and the LED turns off. This sensor is a basic and widely used part in applications such as line-following cars, rotary speed detection, auto data logging on utility meters or other situations where color or distance contrast is sharp.
There is also a short version Photosensor for you to choose.

Photosensor- Long Range3.jpg


  • Operating voltage: 4.5 V - 5.5 V.
  • Digital output, 0 or VCC.
  • High resolution sensor;minumum detectable length: 1mm black line.
  • Effective distanceļ¼š2-10mm,optimum:5mm.
  • Indicator LED on board.
  • Size:35*7.5*5mm.
  • Easy to use in obstacle sensoring; White/Black wire tracking


There is a infrared emitter and a receiver on this module, the emitter always emit infrared ray. When the infrared light emitted by the emitter gets reflected on a surface that blocked it, the phototransistor can pick up the signal. with this way, this module can be used to detect if there is a obstacle in the measuring range. It can be also use to do White/Black wire tracking because the black wire absorb the rays while the white wire reflect the rays.


Connect the Photosensor to your Arduino/Crowduino power supply pin and digital pins. You can can connect the "s" terminal to any of your arduino Pins,like the "D6" as belows:


1.Copy the following program to Arduino IDE and upload to your Arduino/Crowduino:

void setup()  {
void loop()  {
  while(1)  {
    if(digitalRead(6)==LOW)  {
      Serial.println("Somebody is here.");
    else  {

2.Open the Serial moniter , and set the baudrate to 9600, you will see that When somebody is in front of the sensor , the Serial Monitor will output "Somebody is here.".Or, the Serial Monitor output "Nobody."

Photosensor- Short Range test result.jpg


File:SH178 datasheet.pdf