DESCRIPTION
The Saleng – Tracker module is a compact reflective
infrared sensor module designed for detecting the
presence or absence of an IR reflective surface (e.g.
light or dark line) in front of its optical elements. The
module uses the TCRT5000 IR pair while its output is fed
to a Schmitt triggered gate producing reliable digital
output. It has a Digital Output pin labeled DO and
another with an inverted output signal labeled ~DO. DO
is high when a reflective surface (e.g. white surface)
comes within range and thereby reflecting back the
emitter’s IR beam back to the IR receiver on the board.
DO is low when no reflective surface (e.g. dark surface)
is detected. ~DO’s output is the inverse of DO. The
absence of a sensitivity/calibration adjustment
potentiometer makes this module easy to use with its
digital outputs optimized for dark/light line detection in
robotic applications. An Analog Output pin named AO is
also available and is tied to the output of the photo
diode. This may be useful for distance or obstacle
sensing. The tracker module is part of Layad Circuits’
Saleng series of innovation-starter products.

• FEATURES
•  Detector Type: Phototransistor
•  Input Voltage: 3.3V – 5V
•  Typical Current Consumption: <40mA
•  Peak Current (Vin=5V): 80mA
•  Digital Output Effective Distance Range: ~10mm
•  Analog Output Effective Distance Range:
• ~100mm
•  Emitter Wavelength: 950nm
•  Daylight Blocking Filter
•  Digital Output with Inverted Output
•  Analog Output
•  Small form factor, board dimensions: 15x38mm
• TYPICAL APPLICATIONS
•  Line Following Robot
•  Limit Sensor
•  Object Counter
•  Speed Mater / Tachometer
•  General Obstacle sensing
•  Distance Sensing

APPLICATION NOTES
Line Tracing/Line Follower Robot
The Saleng – Tracker module may be used with a
microcontroller based mobile robot to quickly detect
light and dark surfaces. The module maybe installed
under the chassis at a distance of about 1cm from the
floor. Only the DO (or the ~DO if you need an inverted
logic e.g. low when reflections are detected) is needed
in this case. The AO may be left unconnected.

const byte salengTrackerDO = 2;   
const byte led= 13;    
void setup() 
{ 
Serial.begin(115200); 
pinMode(salengTrackerDO, INPUT);       
pinMode(led, OUTPUT);           
}
void loop() 
{ 
if(digitalRead(salengTrackerDO) == HIGH) 
{ 
digitalWrite(led,HIGH);      
// if a reflective surface is  
// detected then turn LED on 
Serial.println("Light!"); 
} 
else 
{ 
digitalWrite(led,LOW);       
// if no reflective surface is  
// detected then turn LED off 
Serial.println("Dark!"); 
} 
}

It goes without saying that if a mobile robot is involved,
the above sketch will need to include the motor control
algorithm.
Distance or Obstacle Sensing with the Analog Output
2
The Saleng-Tracker module has an analog output with a
voltage that is approximately proportional to the
distance of a reflector in front of the optical elements.
Typically, the sensor is effective when the reflective
surface is at around 100mm (10cm) of the optical
elements. In actual test using an ordinary white paper
as reflector and an Arduino, there are detectable
changes in voltage up to around 200mm (20cm).
Take note though that the analog output voltage does
not have a linear relationship with distance. It is advised
to perform actual experiments to obtain a calibration
curve or look up table.

In actual tests, the typical maximum useable distance
range is 15 to 20mm. To be on the safe side, a 10mm or
lower floor-to-optical sensor distance is advised.
Because the digital output come from Schmitt triggered
gates, DO and ~DO will readily work with a 5V or 3.3V
microcontroller.
Example Saleng Uno/ Arduino Code following figure 2
wiring to demonstrate line tracking ability: