3.0 13 I/O pins. The microcontroller is responsible for

3.0       METHODOLOGY

This section
includes the development of the block diagram and the block by block
development of the circuit diagram

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3.1       Block
diagram

The block
diagram shows at a glance the summary of the whole circuitry and as well made
easy the explanation of the operation of the system. Shown below is the block
diagram of the alarm system that is aimed at detecting motion as well as
motion.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.1.1   System description

The
block diagram is composed of the power supply unit, smoke sensor unit, the
motion sensor unit, the controller code, the microcontroller unit and the alarm
unit.

Power supply unit

This
unit provides the needed power supply for the whole system. The supply is
expect to be 5V for the motion sensor and the controller unit while a 12V is
meant to power the smoke sensor and the alarm unit

The smoke sensor unit

This
unit makes use of the ionization smoke detector device. Virtually all
ionization smoke detectors for residential smoke alarm use approximately
0.9mirocuries of americium-241(241Am), to create a source of ions.
These are radioactive decays. R. J. BRUCE, DENNIS WOLF, MARCH, 2012

The
ions are attracted to the smoke particles entering the chamber. The
concentrated charge changes the voltage on a floated plate by releasing alpha
particles which collide with air to produce ion to create a potential
difference between two electrodes. This is used to drive a LED section of an
opto-isolator whose transistor is used to switch the input of a
microcontroller.

The motion sensor unit

This
unit employs the passive infrared (PIR) motion detector. The PIR detects heat
energy emitted by object moving across the view of heat sensor of the motion
detection system. The PIR detector employs a group of radiation sensors coupled
through amplifiers to a logic circuit. The sensors detect changes in ambient
infrared radiation. These changes are fed to a comparator circuit which
eventually switches as result detecting a motion. The output of the motion
sensor is also fed to the microcontroller unit in order to switch the alarm
unit.

The microcontroller unit

 This unit employs the 16F84 microcontroller.
This is an eighteen pin two port chip with 13 I/O pins. The microcontroller is
responsible for sensing the response from the sensors and thus triggers the
alarm unit.

The
microcontroller is able to perform this operation with the help of the software
that is embedded into it.

 

 

The alarm unit

The
alarm is a buzzer system that is turned ON by the operation of the
microcontroller. The operation is determined by the code that is embedded in
the controller. The output of the microcontroller is made to operate a
transistor switching system which in turn completes the circuit of the alarm
unit

The controller code

The
code is developed using assembly language.

The
software performs the following operations in an infinite loop:

1.
Takes the outputs from the smoke and motion detectors as input to the
microcontroller

2.
Detects if the input is smoke or motion.

3.
Cause the microcontroller to switch ON the alarm unit.

The
assembly code is to be assembled using an assembler and the resulting hex
loaded into the microcontroller using a programmer.

 

3.2       Circuit analysis

These include
the development of the power supply unit, the smoke sensor circuit, the motion
sensor circuit, the microcontroller circuit and the alarm circuit.

3.2.1    Power supply circuit.

The system does
not require a complicated power unit. A simple power unit is designed to power
the system

Basically
the power is expected to supply 5V and 12Vdc to the circuit. The development is
shown in the block diagram to represent each section.

 

 

 

 

The
block illustrates the block sectioning of the power supply and are further
detailed as follow,

3.2.1.1 Transformation
Since
the major supply of power is the 240Va.c, there is need for this voltage value
to be stepped by transformation mean to smaller value of 12v.

The
transformer used for this purpose is a twelve volts transformer and the output
is fed to the rectification section.

 

                                                                                                                                  

t

 

                                                                                                                                  

                                                                                                                                   

 

Shown in fig 3.1.1 is
the circuit of the transformation section and the output waveform.

The
peak voltage is given by

3.2.1.2 Rectification 

This
section employed the bridge type of full-wave rectification.

The
choice of diode is determined by the peak voltage and the maximum load current.

The
peak voltage in this respect is 16.97V and the maximum load current is estimated
to 0.5A.

In
selecting the bridge diodes, it was found that the 1N4007 fits in as it is
shown from its data.

V

 

Shown below is the bridge connection and its input
and output waveforms.

 

 

 

 

                                                       

 

3.2.1.3 Filtration

The capacitor is
connected across the output of the rectifier to filter out ac ripples from the
output.

To determine the value
of capacitor, the load current is given great consideration

Ripple frequency is
100Hz (for full wave) and the charging time  

Maximum
charging voltage on the capacitor

    =     

Average
output voltage = V – Vcap     =         

Vpeak   = 

Therefore
16.97 –

Therefore
C =  

Preferred
Value = 1,000

Shown below is the
circuit of the rectification and filtration section and the waveforms.

 

 

 

 

 

 

3.2.1.4 Regulation

 A regulation IC is used to obtain the desired
5Vdc at this section.

The
7805 is a regulator IC that regulates for 5V output at 1A with its input
varying between 6.5V and 18V.

Shown
below is the full circuit of the power supply.

 

 

 

 

 

 

3.3       Smoke sensor circuit

This
section makes use of the ionization smoke detector device. Virtually all
ionization detectors for residential smoke alarms use approximately 0.9
microcuries of americium-241(241Am), to create a source of ions.
This radioactive isotope decays the ions attached to smoke particles entering
the chamber and drift much more slowly. The accumulated charge in the upper
region changes the voltage on the floated plate that is monitored by an
amplifier by emitting alpha particles (high-energy helium nuclei), which
collide with air molecules to produce ions. The ions drift between electrodes
and establish an equilibrium charge or current that is monitored continuously
by an electronic circuit JOSEPH, M. May, 2000.

Usually
the output from the sensor is in form of a voltage output which is used to
drive a LED section of an opto-isolator whose transistor section is used to
switch the input of a microcontroller.

The
basic circuit is as shown below, 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The output of
the sensor drops from 12V to about 8V whenever particles of smoke accumulate at
the ionization chamber. This potential difference is used to drive the LED
section of the opto coupler. The use of 1K resistor in series with the LED
limit the current to about 4mA and the receiver transistor switches to
saturation causing the input of the microcontroller to be at logic zero. Usually
10K resistors are used as pull up for the inputs of microcontrollers.  

 

3.4       Motion sensor circuit

This section
used the PIR motion sensor. The PIR (Passive Infra-Red) Sensor is a
pyroelectric device capable of detecting motion by measuring changes in the
infrared levels emitted by surrounding objects. The motion is detected by
giving out a high signal from the output pin which is fed to drive a transistor
circuit that drives the input of the microcontroller.

 

 

 

 

 

 

 

 

 

3.5       The microcontroller circuit

The
microcontroller circuit is composed of the clocking circuit which is a crystal
oscillator and capacitor circuit. The purpose is to clock the controller so as
to execute the codes embedded in it. Middle range clocking is chosen (which is
a combination of 4MHz crystal and 33pF capacitor). The microcontroller employed
is the PIC16F84 microcontroller. It is an eighteen pin two port chip with 13
I/O pins. The microcontroller takes in the inputs from the motion and smoke
sensors and drives the alarm unit. The code embedded in the microcontroller
determines how the alarm would be driven.

 

 

 

 

 

 

 

                           

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.6       Alarm unit

The
alarm is a buzzer system that is turned on by the operation of the controller.
The operation is determined by the code that is embedded in the
controller. 

The
output of the microcontroller is made to operate a transistor switching system
which in turn completes the circuit of the buzzer.

Shown
in figure below is the circuit of the alarm.

                                                                                                                                 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.7       Complete circuit diagram

The sections
were put together to develop the complete circuit diagram as shown in figure
3.6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 3.0       METHODOLOGY

This section
includes the development of the block diagram and the block by block
development of the circuit diagram

3.1       Block
diagram

The block
diagram shows at a glance the summary of the whole circuitry and as well made
easy the explanation of the operation of the system. Shown below is the block
diagram of the alarm system that is aimed at detecting motion as well as
motion.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.1.1   System description

The
block diagram is composed of the power supply unit, smoke sensor unit, the
motion sensor unit, the controller code, the microcontroller unit and the alarm
unit.

Power supply unit

This
unit provides the needed power supply for the whole system. The supply is
expect to be 5V for the motion sensor and the controller unit while a 12V is
meant to power the smoke sensor and the alarm unit

The smoke sensor unit

This
unit makes use of the ionization smoke detector device. Virtually all
ionization smoke detectors for residential smoke alarm use approximately
0.9mirocuries of americium-241(241Am), to create a source of ions.
These are radioactive decays. R. J. BRUCE, DENNIS WOLF, MARCH, 2012

The
ions are attracted to the smoke particles entering the chamber. The
concentrated charge changes the voltage on a floated plate by releasing alpha
particles which collide with air to produce ion to create a potential
difference between two electrodes. This is used to drive a LED section of an
opto-isolator whose transistor is used to switch the input of a
microcontroller.

The motion sensor unit

This
unit employs the passive infrared (PIR) motion detector. The PIR detects heat
energy emitted by object moving across the view of heat sensor of the motion
detection system. The PIR detector employs a group of radiation sensors coupled
through amplifiers to a logic circuit. The sensors detect changes in ambient
infrared radiation. These changes are fed to a comparator circuit which
eventually switches as result detecting a motion. The output of the motion
sensor is also fed to the microcontroller unit in order to switch the alarm
unit.

The microcontroller unit

 This unit employs the 16F84 microcontroller.
This is an eighteen pin two port chip with 13 I/O pins. The microcontroller is
responsible for sensing the response from the sensors and thus triggers the
alarm unit.

The
microcontroller is able to perform this operation with the help of the software
that is embedded into it.

 

 

The alarm unit

The
alarm is a buzzer system that is turned ON by the operation of the
microcontroller. The operation is determined by the code that is embedded in
the controller. The output of the microcontroller is made to operate a
transistor switching system which in turn completes the circuit of the alarm
unit

The controller code

The
code is developed using assembly language.

The
software performs the following operations in an infinite loop:

1.
Takes the outputs from the smoke and motion detectors as input to the
microcontroller

2.
Detects if the input is smoke or motion.

3.
Cause the microcontroller to switch ON the alarm unit.

The
assembly code is to be assembled using an assembler and the resulting hex
loaded into the microcontroller using a programmer.

 

3.2       Circuit analysis

These include
the development of the power supply unit, the smoke sensor circuit, the motion
sensor circuit, the microcontroller circuit and the alarm circuit.

3.2.1    Power supply circuit.

The system does
not require a complicated power unit. A simple power unit is designed to power
the system

Basically
the power is expected to supply 5V and 12Vdc to the circuit. The development is
shown in the block diagram to represent each section.

 

 

 

 

The
block illustrates the block sectioning of the power supply and are further
detailed as follow,

3.2.1.1 Transformation
Since
the major supply of power is the 240Va.c, there is need for this voltage value
to be stepped by transformation mean to smaller value of 12v.

The
transformer used for this purpose is a twelve volts transformer and the output
is fed to the rectification section.

 

                                                                                                                                  

t

 

                                                                                                                                  

                                                                                                                                   

 

Shown in fig 3.1.1 is
the circuit of the transformation section and the output waveform.

The
peak voltage is given by

3.2.1.2 Rectification 

This
section employed the bridge type of full-wave rectification.

The
choice of diode is determined by the peak voltage and the maximum load current.

The
peak voltage in this respect is 16.97V and the maximum load current is estimated
to 0.5A.

In
selecting the bridge diodes, it was found that the 1N4007 fits in as it is
shown from its data.

V

 

Shown below is the bridge connection and its input
and output waveforms.

 

 

 

 

                                                       

 

3.2.1.3 Filtration

The capacitor is
connected across the output of the rectifier to filter out ac ripples from the
output.

To determine the value
of capacitor, the load current is given great consideration

Ripple frequency is
100Hz (for full wave) and the charging time  

Maximum
charging voltage on the capacitor

    =     

Average
output voltage = V – Vcap     =         

Vpeak   = 

Therefore
16.97 –

Therefore
C =  

Preferred
Value = 1,000

Shown below is the
circuit of the rectification and filtration section and the waveforms.

 

 

 

 

 

 

3.2.1.4 Regulation

 A regulation IC is used to obtain the desired
5Vdc at this section.

The
7805 is a regulator IC that regulates for 5V output at 1A with its input
varying between 6.5V and 18V.

Shown
below is the full circuit of the power supply.

 

 

 

 

 

 

3.3       Smoke sensor circuit

This
section makes use of the ionization smoke detector device. Virtually all
ionization detectors for residential smoke alarms use approximately 0.9
microcuries of americium-241(241Am), to create a source of ions.
This radioactive isotope decays the ions attached to smoke particles entering
the chamber and drift much more slowly. The accumulated charge in the upper
region changes the voltage on the floated plate that is monitored by an
amplifier by emitting alpha particles (high-energy helium nuclei), which
collide with air molecules to produce ions. The ions drift between electrodes
and establish an equilibrium charge or current that is monitored continuously
by an electronic circuit JOSEPH, M. May, 2000.

Usually
the output from the sensor is in form of a voltage output which is used to
drive a LED section of an opto-isolator whose transistor section is used to
switch the input of a microcontroller.

The
basic circuit is as shown below, 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The output of
the sensor drops from 12V to about 8V whenever particles of smoke accumulate at
the ionization chamber. This potential difference is used to drive the LED
section of the opto coupler. The use of 1K resistor in series with the LED
limit the current to about 4mA and the receiver transistor switches to
saturation causing the input of the microcontroller to be at logic zero. Usually
10K resistors are used as pull up for the inputs of microcontrollers.  

 

3.4       Motion sensor circuit

This section
used the PIR motion sensor. The PIR (Passive Infra-Red) Sensor is a
pyroelectric device capable of detecting motion by measuring changes in the
infrared levels emitted by surrounding objects. The motion is detected by
giving out a high signal from the output pin which is fed to drive a transistor
circuit that drives the input of the microcontroller.

 

 

 

 

 

 

 

 

 

3.5       The microcontroller circuit

The
microcontroller circuit is composed of the clocking circuit which is a crystal
oscillator and capacitor circuit. The purpose is to clock the controller so as
to execute the codes embedded in it. Middle range clocking is chosen (which is
a combination of 4MHz crystal and 33pF capacitor). The microcontroller employed
is the PIC16F84 microcontroller. It is an eighteen pin two port chip with 13
I/O pins. The microcontroller takes in the inputs from the motion and smoke
sensors and drives the alarm unit. The code embedded in the microcontroller
determines how the alarm would be driven.

 

 

 

 

 

 

 

                           

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.6       Alarm unit

The
alarm is a buzzer system that is turned on by the operation of the controller.
The operation is determined by the code that is embedded in the
controller. 

The
output of the microcontroller is made to operate a transistor switching system
which in turn completes the circuit of the buzzer.

Shown
in figure below is the circuit of the alarm.

                                                                                                                                 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.7       Complete circuit diagram

The sections
were put together to develop the complete circuit diagram as shown in figure
3.6