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

3.0       METHODOLOGYThis sectionincludes the development of the block diagram and the block by blockdevelopment of the circuit diagram3.1       Blockdiagram The blockdiagram shows at a glance the summary of the whole circuitry and as well madeeasy the explanation of the operation of the system. Shown below is the blockdiagram of the alarm system that is aimed at detecting motion as well asmotion.                       3.1.1   System descriptionTheblock diagram is composed of the power supply unit, smoke sensor unit, themotion sensor unit, the controller code, the microcontroller unit and the alarmunit.

Power supply unitThisunit provides the needed power supply for the whole system. The supply isexpect to be 5V for the motion sensor and the controller unit while a 12V ismeant to power the smoke sensor and the alarm unitThe smoke sensor unitThisunit makes use of the ionization smoke detector device. Virtually allionization smoke detectors for residential smoke alarm use approximately0.9mirocuries of americium-241(241Am), to create a source of ions.These are radioactive decays. R. J. BRUCE, DENNIS WOLF, MARCH, 2012Theions are attracted to the smoke particles entering the chamber.

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Theconcentrated charge changes the voltage on a floated plate by releasing alphaparticles which collide with air to produce ion to create a potentialdifference between two electrodes. This is used to drive a LED section of anopto-isolator whose transistor is used to switch the input of amicrocontroller.The motion sensor unitThisunit employs the passive infrared (PIR) motion detector. The PIR detects heatenergy emitted by object moving across the view of heat sensor of the motiondetection system.

The PIR detector employs a group of radiation sensors coupledthrough amplifiers to a logic circuit. The sensors detect changes in ambientinfrared radiation. These changes are fed to a comparator circuit whicheventually switches as result detecting a motion. The output of the motionsensor is also fed to the microcontroller unit in order to switch the alarmunit. The microcontroller unit This unit employs the 16F84 microcontroller.

This is an eighteen pin two port chip with 13 I/O pins. The microcontroller isresponsible for sensing the response from the sensors and thus triggers thealarm unit.Themicrocontroller is able to perform this operation with the help of the softwarethat is embedded into it.  The alarm unitThealarm is a buzzer system that is turned ON by the operation of themicrocontroller.

The operation is determined by the code that is embedded inthe controller. The output of the microcontroller is made to operate atransistor switching system which in turn completes the circuit of the alarmunitThe controller codeThecode is developed using assembly language.Thesoftware performs the following operations in an infinite loop:1.Takes the outputs from the smoke and motion detectors as input to themicrocontroller2.

Detects if the input is smoke or motion.3.Cause the microcontroller to switch ON the alarm unit.Theassembly code is to be assembled using an assembler and the resulting hexloaded into the microcontroller using a programmer.  3.2       Circuit analysisThese includethe development of the power supply unit, the smoke sensor circuit, the motionsensor circuit, the microcontroller circuit and the alarm circuit.3.2.

1    Power supply circuit.The system doesnot require a complicated power unit. A simple power unit is designed to powerthe systemBasicallythe power is expected to supply 5V and 12Vdc to the circuit. The development isshown in the block diagram to represent each section.     Theblock illustrates the block sectioning of the power supply and are furtherdetailed as follow, 3.2.1.

1 Transformation Sincethe major supply of power is the 240Va.c, there is need for this voltage valueto be stepped by transformation mean to smaller value of 12v.Thetransformer used for this purpose is a twelve volts transformer and the outputis fed to the rectification section.                                                                                                                                    t                                                                                                                                                                                                                                                                           Shown in fig 3.

1.1 isthe circuit of the transformation section and the output waveform.Thepeak voltage is given by 3.

2.1.2 Rectification  Thissection employed the bridge type of full-wave rectification. Thechoice of diode is determined by the peak voltage and the maximum load current.Thepeak voltage in this respect is 16.97V and the maximum load current is estimatedto 0.5A.Inselecting the bridge diodes, it was found that the 1N4007 fits in as it isshown from its data.

V   Shown below is the bridge connection and its inputand output waveforms.                                                              3.2.1.

3 FiltrationThe capacitor isconnected across the output of the rectifier to filter out ac ripples from theoutput. To determine the valueof capacitor, the load current is given great consideration Ripple frequency is100Hz (for full wave) and the charging time  Maximumcharging voltage on the capacitor     =      Averageoutput voltage = V – Vcap     =          Vpeak   =  Therefore16.97 – ThereforeC =   PreferredValue = 1,000Shown below is thecircuit of the rectification and filtration section and the waveforms.      3.2.1.

4 Regulation A regulation IC is used to obtain the desired5Vdc at this section. The7805 is a regulator IC that regulates for 5V output at 1A with its inputvarying between 6.5V and 18V.Shownbelow is the full circuit of the power supply.       3.3       Smoke sensor circuitThissection makes use of the ionization smoke detector device. Virtually allionization detectors for residential smoke alarms use approximately 0.

9microcuries of americium-241(241Am), to create a source of ions.This radioactive isotope decays the ions attached to smoke particles enteringthe chamber and drift much more slowly. The accumulated charge in the upperregion changes the voltage on the floated plate that is monitored by anamplifier by emitting alpha particles (high-energy helium nuclei), whichcollide with air molecules to produce ions.

The ions drift between electrodesand establish an equilibrium charge or current that is monitored continuouslyby an electronic circuit JOSEPH, M. May, 2000.Usuallythe output from the sensor is in form of a voltage output which is used todrive a LED section of an opto-isolator whose transistor section is used toswitch the input of a microcontroller.Thebasic circuit is as shown below,                     The output ofthe sensor drops from 12V to about 8V whenever particles of smoke accumulate atthe ionization chamber. This potential difference is used to drive the LEDsection of the opto coupler. The use of 1K resistor in series with the LEDlimit the current to about 4mA and the receiver transistor switches tosaturation causing the input of the microcontroller to be at logic zero. Usually10K resistors are used as pull up for the inputs of microcontrollers.   3.

4       Motion sensor circuitThis sectionused the PIR motion sensor. The PIR (Passive Infra-Red) Sensor is apyroelectric device capable of detecting motion by measuring changes in theinfrared levels emitted by surrounding objects. The motion is detected bygiving out a high signal from the output pin which is fed to drive a transistorcircuit that drives the input of the microcontroller.          3.5       The microcontroller circuitThemicrocontroller circuit is composed of the clocking circuit which is a crystaloscillator and capacitor circuit. The purpose is to clock the controller so asto execute the codes embedded in it. Middle range clocking is chosen (which isa combination of 4MHz crystal and 33pF capacitor). The microcontroller employedis the PIC16F84 microcontroller.

It is an eighteen pin two port chip with 13I/O pins. The microcontroller takes in the inputs from the motion and smokesensors and drives the alarm unit. The code embedded in the microcontrollerdetermines how the alarm would be driven.

                                                  3.6       Alarm unitThealarm 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 thecontroller.  Theoutput of the microcontroller is made to operate a transistor switching systemwhich in turn completes the circuit of the buzzer. Shownin figure below is the circuit of the alarm.                                                                                                                                                        3.7       Complete circuit diagramThe sectionswere put together to develop the complete circuit diagram as shown in figure3.

6                         3.0       METHODOLOGYThis sectionincludes the development of the block diagram and the block by blockdevelopment of the circuit diagram3.1       Blockdiagram The blockdiagram shows at a glance the summary of the whole circuitry and as well madeeasy the explanation of the operation of the system.

Shown below is the blockdiagram of the alarm system that is aimed at detecting motion as well asmotion.                       3.1.1   System descriptionTheblock diagram is composed of the power supply unit, smoke sensor unit, themotion sensor unit, the controller code, the microcontroller unit and the alarmunit.

Power supply unitThisunit provides the needed power supply for the whole system. The supply isexpect to be 5V for the motion sensor and the controller unit while a 12V ismeant to power the smoke sensor and the alarm unitThe smoke sensor unitThisunit makes use of the ionization smoke detector device. Virtually allionization smoke detectors for residential smoke alarm use approximately0.9mirocuries of americium-241(241Am), to create a source of ions.These are radioactive decays. R. J.

BRUCE, DENNIS WOLF, MARCH, 2012Theions are attracted to the smoke particles entering the chamber. Theconcentrated charge changes the voltage on a floated plate by releasing alphaparticles which collide with air to produce ion to create a potentialdifference between two electrodes. This is used to drive a LED section of anopto-isolator whose transistor is used to switch the input of amicrocontroller.The motion sensor unitThisunit employs the passive infrared (PIR) motion detector. The PIR detects heatenergy emitted by object moving across the view of heat sensor of the motiondetection system. The PIR detector employs a group of radiation sensors coupledthrough amplifiers to a logic circuit.

The sensors detect changes in ambientinfrared radiation. These changes are fed to a comparator circuit whicheventually switches as result detecting a motion. The output of the motionsensor is also fed to the microcontroller unit in order to switch the alarmunit. The microcontroller unit This unit employs the 16F84 microcontroller.

This is an eighteen pin two port chip with 13 I/O pins. The microcontroller isresponsible for sensing the response from the sensors and thus triggers thealarm unit.Themicrocontroller is able to perform this operation with the help of the softwarethat is embedded into it.  The alarm unitThealarm is a buzzer system that is turned ON by the operation of themicrocontroller. The operation is determined by the code that is embedded inthe controller. The output of the microcontroller is made to operate atransistor switching system which in turn completes the circuit of the alarmunitThe controller codeThecode is developed using assembly language.Thesoftware performs the following operations in an infinite loop:1.Takes the outputs from the smoke and motion detectors as input to themicrocontroller2.

Detects if the input is smoke or motion.3.Cause the microcontroller to switch ON the alarm unit.Theassembly code is to be assembled using an assembler and the resulting hexloaded into the microcontroller using a programmer.  3.2       Circuit analysisThese includethe development of the power supply unit, the smoke sensor circuit, the motionsensor circuit, the microcontroller circuit and the alarm circuit.3.

2.1    Power supply circuit.The system doesnot require a complicated power unit. A simple power unit is designed to powerthe systemBasicallythe power is expected to supply 5V and 12Vdc to the circuit.

The development isshown in the block diagram to represent each section.     Theblock illustrates the block sectioning of the power supply and are furtherdetailed as follow, 3.2.1.1 Transformation Sincethe major supply of power is the 240Va.c, there is need for this voltage valueto be stepped by transformation mean to smaller value of 12v.

Thetransformer used for this purpose is a twelve volts transformer and the outputis fed to the rectification section.                                                                                                                                    t                                                                                                                                                                                                                                                                           Shown in fig 3.1.1 isthe circuit of the transformation section and the output waveform.Thepeak voltage is given by 3.2.1.2 Rectification  Thissection employed the bridge type of full-wave rectification.

Thechoice of diode is determined by the peak voltage and the maximum load current.Thepeak voltage in this respect is 16.97V and the maximum load current is estimatedto 0.5A.

Inselecting the bridge diodes, it was found that the 1N4007 fits in as it isshown from its data. V   Shown below is the bridge connection and its inputand output waveforms.                                                              3.2.1.3 FiltrationThe capacitor isconnected across the output of the rectifier to filter out ac ripples from theoutput. To determine the valueof capacitor, the load current is given great consideration Ripple frequency is100Hz (for full wave) and the charging time  Maximumcharging voltage on the capacitor     =      Averageoutput voltage = V – Vcap     =          Vpeak   =  Therefore16.97 – ThereforeC =   PreferredValue = 1,000Shown below is thecircuit of the rectification and filtration section and the waveforms.

      3.2.1.4 Regulation A regulation IC is used to obtain the desired5Vdc at this section. The7805 is a regulator IC that regulates for 5V output at 1A with its inputvarying between 6.5V and 18V.

Shownbelow is the full circuit of the power supply.       3.3       Smoke sensor circuitThissection makes use of the ionization smoke detector device. Virtually allionization detectors for residential smoke alarms use approximately 0.9microcuries of americium-241(241Am), to create a source of ions.This radioactive isotope decays the ions attached to smoke particles enteringthe chamber and drift much more slowly. The accumulated charge in the upperregion changes the voltage on the floated plate that is monitored by anamplifier by emitting alpha particles (high-energy helium nuclei), whichcollide with air molecules to produce ions. The ions drift between electrodesand establish an equilibrium charge or current that is monitored continuouslyby an electronic circuit JOSEPH, M.

May, 2000.Usuallythe output from the sensor is in form of a voltage output which is used todrive a LED section of an opto-isolator whose transistor section is used toswitch the input of a microcontroller.Thebasic circuit is as shown below,                     The output ofthe sensor drops from 12V to about 8V whenever particles of smoke accumulate atthe ionization chamber. This potential difference is used to drive the LEDsection of the opto coupler.

The use of 1K resistor in series with the LEDlimit the current to about 4mA and the receiver transistor switches tosaturation causing the input of the microcontroller to be at logic zero. Usually10K resistors are used as pull up for the inputs of microcontrollers.   3.4       Motion sensor circuitThis sectionused the PIR motion sensor. The PIR (Passive Infra-Red) Sensor is apyroelectric device capable of detecting motion by measuring changes in theinfrared levels emitted by surrounding objects. The motion is detected bygiving out a high signal from the output pin which is fed to drive a transistorcircuit that drives the input of the microcontroller.          3.

5       The microcontroller circuitThemicrocontroller circuit is composed of the clocking circuit which is a crystaloscillator and capacitor circuit. The purpose is to clock the controller so asto execute the codes embedded in it. Middle range clocking is chosen (which isa combination of 4MHz crystal and 33pF capacitor).

The microcontroller employedis the PIC16F84 microcontroller. It is an eighteen pin two port chip with 13I/O pins. The microcontroller takes in the inputs from the motion and smokesensors and drives the alarm unit. The code embedded in the microcontrollerdetermines how the alarm would be driven.                                                  3.6       Alarm unitThealarm 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 thecontroller.  Theoutput of the microcontroller is made to operate a transistor switching systemwhich in turn completes the circuit of the buzzer. Shownin figure below is the circuit of the alarm.                                                                                                                                                        3.7       Complete circuit diagramThe sectionswere put together to develop the complete circuit diagram as shown in figure3.6