Fairchild GRB1134 Support

Phototransistor Reflective Object Sensor Kit

All Sensors

Robot Kits

The Fairchild QRB1134 is generally used as a line following sensor.  White reflects light, black does not reflect.  The sensor will needs about a 0.25" to 0.5" black line on a white surface in order to work.  The sensor needs a "pull-up" resistor on each line follower output.  The pull-up resistor does exactly what it sounds like, it pulls up the value to 5 volts.  The reason you pull up is to eliminate the effects of a drifting circuit.  If the output is floating so could the value the OOPic reads hence giving erroneous readings.  So when no signal is present the output the OOPic sees is pulled up to 5V.  When the sensor does send a signal it has enough current to overcome the pull-up resistor and ground (~0 Volts) the output.  A capacitor to each of the outputs is recommended to ground to eliminate spikes and any other spurious readings and smooth out the outputs (polarity capacitors will have one leg longer than the other, the longer leg is the "+" leg).  The schematic below shows how to wire a single sensor.