Line Following Obstacle Avoiding Maze solving Robot part 4
Continue from Part 3
The
physics which govern reflection of visible and infrared light are the
same. IR LED’s are easily available, and so are the sensors to
detect IR radiation. Unless shielded properly, ambient radiation may
affect these readings. You can “smooth” the data after receiving,
but proper placement and shielding of
sensors
will go a long way to help get accurate readings off the track.
You’ve two options now, to purchase a manufactured IR sensor
module,
or to build one yourself. A manufactured one has many benefits, like
less susceptibility to noise and easy tuning and integration. The
biggest disadvantage of a manufactured module is…it is not
configurable. Exactly the opposite is true for a DIY module. If
you’re only just starting out, it will probably save you quite a
bit of trouble if you purchase one, but it does have its limitations.
Read this full section out before you make a decision. Sensor modules
in this sense refers to a circuit which can sense reflected light and
convert it into quantity which can be interpreted by a
microcontroller…voltage. We call it modules, because sometimes more
than one sensor pair is integrated, forming an array of Sensors.
When IR read black color the output goes low hence the LEG will not glow and both motor moves forward. When IR read white color the output goes high hence the LED will glow and the motor moves reverse and forward This Robot follows a black maze by sensing the environment using IR sensors. It is programmed to follow the line perfectly with both the motors rotating in forward direction. Any deviations from the line will adjust the motor accordingly to ensure it follows the right path again. Two sensors are used for tracing the black line, and the left most, right most sensor are used for taking decision on junctions. The basic principle applied for following the line is the amount of reflection variation caused by white and black surfaces. It differentiates depending on the amount of reflection and follows the correct path.
IR
sensors detection white color:
Interfacing
IR senor to Arduino board:
Pin:
Sensor
digital pin 8 and 9
OBSTACLE
SENSOR:
Sharp
GP2D12 Analog Distance Sensor
Specifications:
Supply
Voltage :5.0
Operating
Temperature : -10 - +60 °C
Distance
Measuring Range † 10 - 80 cm
Output
Terminal Voltage (L=80 cm) 0.25 0.4 0.55 V
Output change at L=80 cm to 10 cm 1.75 2.0 2.25 V
Connecting
and Testing:
Connect
the GP2D12 to your analog to digital converter as shown in the
circuit on the previous page.
The
potentiometer connected to the Vref pin on the ADC0831 is being used
as a voltage divider to set the
reference
voltage to 2.55 volts. On the ADC0831 this will give a value of 0 to
255 for an input voltage of
0
to 2.55 volts. This gives us a resolution of 0.01 volts per step from
the ADC. If you are using a
different
analog to digital converter, you may want to adjust the potentiometer
to get the best results
from
your particular ADC.
Calibration:
Because
the output of the GP2D12 is not linear, we need a way to determine
what distances correspond
to
what voltages. One way of calibrating your sensor is by measuring the
voltage output of the GP2D12
at
given fixed distances, in centimeters, as shown in the chart below.
Once you have this information
you
can plug these numbers into the EEPROM DATA statements in the
program. The table of data is
used
by a routine in the program to calculate the distances, which are
then displayed on the Debug
Terminal,
along with the voltage output from the sensor.
Voltage
V/S distance
General
Description
The
Sharp GP2D12 is an analog distance sensor that uses infrared to
detect an object between 10 cm
and
80 cm away. The GP2D12 provides a non-linear voltage output in
relation to the distance an object
is
from the sensor and interfaces easily using any analog to digital
converter.
Sensitivity
The
usable range of the GP2D12 is between 10 cm and 80 cm. The readings
for objects closer than 10
cm
are unstable and therefore not usable.
Interfacing
Sharp
GP2D12 to Arduino:
Pin:
-
Analog pin AO
Actuators:
DC
geared motor:
They’re
cheap, and available in multiple variations of speed and torque. Some
even come with gear sets, so you can customize it to best suit your
robot. The disadvantage is you have no internal feedback control.
That means you have no idea of the speed of the motor.
A
word of caution here, the speed mentioned in the motor stats
represents what is called the “no-load” speed of the motor. The
motor will never run at that speed when you fix a chassis and all
your components onto it. Pick a motor with a low voltage rating. This
means, just for example, you should pick a 6V motor over a 24V motor.
Motors with lower ratings are generally lighter.
A
geared DC Motor has a gear assembly attached to the motor. The speed
of motor is counted in terms of rotations of the shaft per minute and
is termed as RPM .The gear assembly helps in increasing the torque
and reducing the speed. Using the correct combination of gears in a
gear motor, its speed can be reduced to any desirable figure. This
concept where gears reduce the speed of the vehicle but increase its
torque is known as gear reduction. This Insight will explore
all the minor and major details that make the gear head and hence the
working of geared DC motor.
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