SENSOR THAT DETECT EYE BLINKING

WEEK 4:

I had made research about the sensor that need to use to detect the eye and I had found a few type of sensor that used as sensor to detect  eye blinking and finally I choose IR sensor because it is suitable for make prototype.

IR Sensor (IR Receiver and IR Emitter)

    The basic principle of IR sensor is based on an IR emitter and an IR receiver. IR emitter will emit infrared continuously when power is supplied to it. On the other hand, the IR receiver will be connected and perform the task of a voltage divider. IR receiver can be imagined as a transistor with its base current  determined by the intensity of IR light received. The  lower the intensity of IR light cause higher resistance between collector-emitter terminals of transistor, and  limiting current from collector to emiiter. This change  of resistance will further change the voltage at the  output of voltage divider. In others word, the greater  the intensity of IR light hitting IR receiver, the lower  the resistance of IR receiver and hence the output mvoltage of voltage divider will decreased. Usually the  IR emitter and IR receiver will be mounted side by side,  pointing to a reflective surface. The further distance  away between emitter and receiver decrease the  amount of infrared light hitting the receiver if the  distance between the sensor and a reflective surface is  fixed.  Since the output voltage from voltage divider varies  with the intensity of IR light, and microcontroller is not  used in this project, a comparator (LM324) is used to show the changes. The eye-blink sensor works by illuminating the eye and/or eyelid area with infrared light, then monitoring the changes in the reflected light using a phototransistor and differentiator circuit. The exact functionality depends greatly on the positioning and aiming of the emitter and detector with respect to the eye.