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.
