AUTOMATIC GRASS CUTTING MACHINE BY USING
PHOTOVOLTAIC SOURCE AND MOTOR SPEED CONTROL
Mr. P. PUGAZHENDIRAN1
Associate professor /HOD OF EEE1
Pugazhifet@gmail.com1
Mr. A. BHARANEETHARAN2
Senior Assistant professor2
barani3e@gmail.com2
N. MOHAMEDNIZAR3
UG Scholar3
mhdnizaaar@gmail.com3
Abstract:
This project is mainly proposal for
reduce the manpower and usage of
electricity. Maximum power point
tracking technique is used to improve the
efficiency of the solar panel. The DC to
DC buck boost converter helps to step up
the DC voltage from the photovoltaic
panel and store the DC voltage in a
battery. It is an automated system for the
purpose of grass cutting. The source is
drive from the solar energy by using
photovoltaic
panels.
The
DC-DC
converter is used to convert the low level
DC voltage into the high level DC voltage.
High level DC voltage helps to operate the
whole system. The system control is done
by the microcontroller. Automation is
achieved
by
using
sensors
and
microcontrollers. Wheels and cutting
operations are done using dc motors. DC
battery is utilized for powering and
standby mode operation of the system.
Introduction:
This project is a proposed model of
the automatic grass cutting machine by
using the non-renewable energy (i.e. solar
energy). The automatic grass cutting
machine is a machine which is going to
perform the grass cutting operation by its
own which means no manpower is required.
This machine consists of the
photovoltaic, dc to dc converter, motor,
controller,
sonar
sensor
and
microcontroller. The photovoltaic is used to
receive the solar energy from the sunlight
and output of the photovoltaic panel is
varying. So the dc to dc converter is used to
convert the low level dc voltage to high
level dc voltage. The dc to dc converter is
act as buck, boost and buck-boost mode of
operation.
The step up dc voltage is stored in dc
battery. The battery is charge by the dc input
which is get from the photovoltaic panel. If
the battery is fully charged then the
controller is disconnected the contact
between dc to dc converter and output
voltage from battery is convert the dc
voltage as step up and step down voltage by
the requirement of the dc motor.
Converter’s mode of operation is
selected by the controller is fully based on
the required of motor and battery. The speed
of the motor is maintained constant. If the
motor torque is increase then boost mode is
activate. If the motor torque is decrease then
buck mode is activate. The dc voltage is step
up and step down by varying the duty cycle.
In this project is only concentrated
on the part of control the dc motor with
constant speed by the photovoltaic source.
Block diagram:
PV Panel
Types of units:


DC TO DC
CONVERTER
BATTERY
DC TO DC
CONVERTER
DC MOTOR


SENSOR
Voltage regulated unit
Battery low/high voltage sensor
unit
Battery charging/motor usage
switch unit
Motor controller unit
MICROCONTROLLER
General block diagram
Photovoltaic panel receives the
sunlight generate low level dc output and
output is varying by the range of irradiance.
So we are using MPPT technique for getting
constant output from the photovoltaic panel.
The DC to DC converter is used to boost
low level voltage to high level voltage
supply. The battery charged by the high
level voltage getting from the DC to DC
converter.
The Dc motor is fully run by the
battery charge. The supply from battery is
not efficient to run the DC motor in constant
speed. So the DC to DC converter is used to
boost the supply which is going to run the
DC motor in constant speed in a loaded
condition also. There are four types of units
available in the main circuit.
Battery low/high voltage sensor
unit:
When the battery is in charging
condition, the connection between battery to
DC motor. The Battery level is maintaining
in the range of the 8 volt to 12 volt. There
are two types of sensing unit is available in
the battery controller part. They are low
level sensing and high level sensing relay.
The low level sensing relay is activate in the
voltage range of 8 volt to 10 volt and the
high level sensing relay is activated in the
voltage range of 8 volt to 12 volt.
In the sensing unit both low and high
level sensing relay activated at a time. The
battery charging, the battery voltage level is
reaches 10 volt means the low level sensing
relay get deactivate and the voltage level is
reaches 12 volt then high level sensing relay is
also deactivated.
Voltage regulated unit:
Basic operating principles:
The voltage regulated unit is to regulate
the input supply and feed into the battery. The
photovoltaic panel output is varying. So the
input voltage is maintains constant by the
voltage regulator.
The working principle of all today
solar cells is essentially the same. It is based
on the photovoltaic effect. In general, the
photovoltaic effect means the generation of
a potential difference at the junction of two
different materials in response to visible or
other radiation.
The basic processes behind the photovoltaic
effect are:
Photovoltaic panel:
Solar energy is generally
present in the form of solar irradiance. The
PV cell works in the principle of
Photoelectric effect; light striking on solar
cell is converted to electric energy. These
cells are made by silicon or other
semiconductor materials. A typical silicon
solar cell generates about 0.5 volts in normal
operation. Large number of solar cells is
connected in series, forming a module to
meet the voltage requirement of the system.
Large number of solar modules is
connected to make arrays. The rating of a
solar module is given by the maximum
output or maximum power it can deliver.
The output of a solar module depends on the
number of cells in the module, type of cell
and the total surface area. The output of a
module changes depending on the amount of
solar irradiance, the angle of the module
with respect to the sun, the temperature of
the module and the voltage at which the load
is drawing power from the module.
1. Generation of the charge carriers due
to the absorption of photons in the
materials that form a junction,
2. Subsequent separation of the photogenerated charge carriers in the
junction,
3. Collection of the photo-generated
charge carriers at the terminals of the
junction.
Band diagram of an idealized solar cell structure at
the open-circuit
Band diagram of an idealized solar cell structure at
the short-circuit
MPPT technique:
Maximum Power Point Tracking,
frequently referred to as MPPT, is an
electronic system that operates the
Photovoltaic (PV) modules in a manner that
allows the modules to produce all the power
they are capable of. MPPT is not a
mechanical tracking system that “physically
moves” the modules to make them point
more directly at the sun. MPPT is a fully
electronic system that varies the electrical
operating point of the modules so that the
modules are able to deliver maximum
available power. Additional power harvested
from the modules is then made available as
increased battery charge current. MPPT can
be used in conjunction with a mechanical
tracking system, but the two systems are
completely different.
To understand how MPPT works,
let’s first consider the operation of a
conventional (non-MPPT) charge controller.
When a conventional controller is charging a
discharged battery, it simply connects the
modules directly to the battery. This forces
the modules to operate at battery voltage,
typically not the ideal operating voltage at
which the modules are able to produce their
maximum available power. The PV Module
Power/Voltage/Current graph shows the
traditional Current/Voltage curve for a
typical 75W module at standard test
conditions of 25°C cell temperature and
1000W/m2 of insulation. This graph also
shows PV module power delivered Vs
module voltage. For the example shown, the
conventional controller simply connects the
module to the battery and therefore forces
the module to operate at 12V. By forcing the
75W module to operate at 12V the
conventional controller artificially limits
power production to≈ 53W.
Typical 75W PV Module Power/Voltage/Current
At Standard Test Conditions
Buck-boost converter:
The buck-boost converter is a step down/up
DC/DC converter. It works in third-quadrant
operation. The output voltage is calculated
by the formula,
Vo =
ton
k
Vin =
Vin
T − ton
k−1
where T is the repeating period T = 1/f, f is
the chopping frequency, ton is the switch-on
time, and k is the conduction duty cycle k =
ton/T. By using this converter it is easy to
obtain the random output voltage, which can
be higher or lower than the input voltage. It
provides great convenience for industrial
applications.
Buck boost circuit diagram
MPPT technique algorithm:
(a) Switch on
(b) Switch off
Converter simulation:
Converter simulation diagram
Solar system simulation:
Solar system simulation
function D
= PO(V,I,T)
persistent P2 P1 dP d dd n;
if isempty(V)
V=20;
end
if isempty(I)
I=0;
end
if isempty(P2)
P2=0;
end
if isempty(P1)
P1=0;
end
if isempty(dP)
dP=0;
end
if isempty(d)
d=1;
end
if isempty(dd)
dd=0;
end
if isempty(n)
n=1;
end
%%%%%%%%%%%%%%%%%%%%%
if (T > n*0.02)
%chu ki lay
mau 0.02s
n = n + 1;
P1=P2;
P2=V*I;
dP=P2-P1;
if (dd==0)
if dP>1
dd=0.01;
d=d+dd;
else
if dP<-1
dd=-0.01;
d=d+dd;
else
dd=0;
end
end
else
if ((dP<1)&&(dP>-1))
dd=0;
d=d+dd;
else
if ((dP/dd)>0)
dd=0.01;
d=d+dd;
else
dd=-0.01;
d=d+dd;
end
end
end
end
D=d/(d+1);
if D<0.1
D=0.1;
d=D/(1-D);
else
if D>0.9
D=0.9;
d=D/(1-D);
else
end
end
end
Final simulation diagram:
Full simulation diagram
Simulation output:
Solar system output power
Converter output power
Working flow chart:
This project concludes that the DC
motor is control in a constant speed by
control circuit. The DC motor maintains in a
constant speed in the condition of the load
applied. The battery is charged by the
photovoltaic panel in a constant voltage. The
output of the photovoltaic panel is varying
but IC LM317T is act as a voltage regulator
and got the varying input from the
photovoltaic and gave the output in constant.
The battery is sensing by the
controller unit continuously it helps to
maintain the constant input to DC motor.
The DC motor speed can be able to maintain
constant and the performance can be done in
proper manner.
Reference:
Conclusion:
Due to the power demand we choose
the renewable energy. So there is no running
cost. The DC motor is operated in low
power with high efficiency. DC-DC
converter is maintaining the output voltage
is constant and high. The sensors are not
affected the environment and animals. It will
be very much useful for the user.
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