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Saturday 16 November 2013

Digital Light Intensity Sensor

Overview


Light Intensity sensor  also known  as photoconductor  or photocell,  is a  device which has a resistance  which  varies according to the amount of light  falling on its  surface. Since  LDR  is  extremely  sensitive  in  visible  light  range,  it  is  well  suited  for  any  application.

Digital Light Intensity Sensor




Features

  • Wide spectral response 
  •  Low cost 
  •  Wide ambient temperature range
Applications

  • Ambient light sensing 
  •  Proximity sensing
Using The Sensor

  • Connect +5v to pin 2 and ground to pin 5 and 6. 
  •  Pin 4 and 5 should be connected to particular transmitter and receiver pin of controller. 
  •  Output pin may be connected to any port pins and can be used to any application.
Working
An  LDR  and  a  normal  resistor  are  wired  in  series  across  a  voltage,  as  shown  in  the circuit  below.  Depending  on  which  is tied to the  5V  and  which  to 0V, the  voltage  at  the  point  between  them,  call  it  the  sensor  node,  will  either  rise  or  fall  with  increasing  light.  If  the  LDR  is  the  component  tied  directly  to  the  5V,  the  sensor  node  will  increase in voltage with increasing light  The  LDR's  resistance  can  reach  10  k  ohms  in  dark  conditions  and  about  100  ohms  in full brightness.  The  circuit  used  for  sensing  light  in  our  system  uses  a  10  kΩ  fixed  resistor  which  is tied  to +5V. Hence the voltage value in this case decreases with increase in light intensity. The  sensor  node  voltage  is  compared  with  the  threshold  voltages  for  different  levels of light intensity corresponding to the four conditions Optimum, dim, dark and night. The  relationship between the resistance RL and light intensity Lux for a    typical LDR is:
                                               RL  = 500 / Lux kΩ    …(3.1)
   With the LDR connected to 5V through a 10K resistor, the output voltage of the DR is:                                      
                                                              Vo = 5*RL  / (RL+10)        … (3.2)
In order to increase the sensitivity of the sensor we must reduce the value of the fixed resistor in series with the sensor. This may be done by putting other resistors in parallel with it.


 Pin Out Details:


ATMEL DIGITAL IO Schematic:
ATMEL DIGITAL IO Code:
 For Code Please Click Here

ATMEL UART Schematic:


ATMEL UART Code:
For Code Click Here.