embeded based human security

8/7/2019 embeded based human security

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EMBEDDED BASED HUMAN DATA SECURITY SYSTEM

Buzzer

E O G

SensorRelay

Drive

Micro

Controller

Powersupply

L C D

Display

Temp.

Sensor

Mech.

model



Electrooculography (EOG) :

Electro-oculography (EOG) is a technology that consists of placing electrodes

on the person¶s forehead around the eyes to record eye movements. The voltage that

exists between the eyes is a very small electrical potential that can be detected using

electrodes. People with certain disabilities may use these systems in order to have

certain communication.

The voltage difference is measured between the cornea and the retina. The

resting potential ranges from 0.4mV to 1mV. However, the voltage difference when

here's an eye movement can be as small as just some microvolts. One electrode is

more positive or negative with respect the ground electrode, therefore, the recorded

signal is either negative or positive.

The Electrooculogram

The human eye is polarized, with the front of the eye being positive and the back of

the eye being negative. This is caused by a concentration of negatively charged nerves

in the retina on the back of the eye. As the eye moves the negative pole moves relative

to the face and this change in the dipole potential can be measured on the skin in

micro volts. To translate this voltage into a position, two sets of electrodes are used to

measure the differential voltage in the vertical and horizontal direction, on this project,

however, just horizontal movements are recorded. The figure below indicates how the

electrodes are placed on the face. The red and black leads measure movement in the

horizontal direction and the white and brown leads measure movement in the vertical



direction. The green sensor is placed behind the ear or on the ear lobe to provide a

ground reference.

Using these leads we can translate each change in voltage into a change in the

eye¶s position. If the eye looks to the right for instance, the positive pole of the eyewill be nearest the right side sensor causing it to read a positive voltage while the back

of the eye will be nearest the left side sensor causing it to read a negative voltage.

From the voltage potential between these two sensors the left/right position of the eye

can be determined. The same technique is used to determine the vertical position. The

eye has a standing electrical potential between front and back, sometimes called the

corneo-fundal potential. The potential is mainly derived from the retinal pigment

epithelium (RPE), and it changes in response to retinal illumination.

The potential decreases for 8±10 min in darkness. Subsequent retinal

illumination causes an initial fall in the standing potential over 60±75 s (the fast

oscillation (FO)), followed by a slow rise for 7±14 min (the light response). These

phenomena arise from ion permeability changes across the basal RPE membrane.



The clinical electro-oculogram (EOG) makes an indirect measurement of the

minimum amplitude of the standing potential in the dark and then again at its peak

after the light rise. This is usually expressed as a ratio of 'light peak to dark through'

and reffered to as the Arden ratio.

The EOG on this project is used as a way to interact with the computer. However,

there are some other uses as well.



Other Applications

� Sleep and dream research

� Eye tracking for marketing purposes

� Reading ability and visual fatigue

� Retinal dysfunction

± Some disorders of the retina exhibit abnormal or absent changes in the

corneal-retinal potential during dark and light adaptation processes.

� Vestibular and balance dysfunction

± Nystagmus: characteristic slow-phase/fast-phase eye movement measurable

by EOG

± prevent drunk drivers from taking to the road.

Thermistors:

Thermistors are thermally sensitive resistors produced with semiconducting materials.



Although RTDs and thermistors are both resistive devices, they differ substantially in

operation and usage, as thermistors are passive semiconductor devices.

Two types of thermistors are available:

1. Negative temperature coefficient (NTC), which decreases its resistance as its

temperature increases, and

2. Positive temperature coefficient (PTC), which increases its resistance as its

temperature decreases.

From the point of view of temperature measurement applications, NTC types are used

far more than PTC ones. Due to its characteristics, PTC types are more frequently

used as thermostats to sense and regulate temperatures (inside ovens, for instance).

Main advantages of (NTC) thermistors are:

y Large change in resistance versus temperature

y Fast time response

y High resistance eliminates the need for four wire measurement

y Small size

y Inexpensive

y High stability

Main disadvantages of thermistors are:

y Non-linear

y Operating temperature limited to approximately -60 to +300 ºCelsius



y Current source required

Operating principle of thermistors

Thermistors can be encapsulated in glass or epoxy considering a big variety of

mechanical models. Most (NTC) thermistors have high resistivities and high negative

coefficients, allowing the NTC thermistors to detect changes in temperature that could

not be observable with RTDs or thermocouples.

For example, it is common to have NTC thermistors exhibiting a negative temperature

coefficient with a change in resistance of about 4.5%/ºC at 30ºC, and about 1.6%/ºC at

155ºC. Common base values can be in the range of a few ohms to mega-ohms.Normally, high-R thermistors are used for ³high´ temperatures (lower than 300ºC),

and low-R thermistors for ³low´ temperatures (higher than -60ºC).

Considering the range of some kilo-ohms to mega-ohms, we can conclude that the

resistance of the wires connecting the instrumentation to the thermistors is

insignificant (in this sense, the three- or four-wire measurement configuration referred

for RTDs are not necessary for NTC thermistors with high-R base values).

Figure 2.6 and Figure 2.7 present typical configurations for two- and four-wire

thermistors circuits (R L stands for the lead resistances); in cases where the series

resistance of the lead configuration is significant, the four-wire circuit can be used. As

far as one current source is used, the calculation of the thermistors resistance is a

straightforward task according to Ohm¶s Law.



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controller). Operational amplifiers (op-amps) are commonly employed to carry out the

amplification of the signal in the signal conditioning stage.

Inputs

Signal inputs accepted by signal conditioners include DC voltage and current,

AC voltage and current, frequency and electric charge. Sensor inputs can be

accelerometer, thermocouple, thermistor, resistance thermometer, strain gauge or

bridge, and LVDT or RVDT. Specialized inputs include encoder, counter or

tachometer, timer or clock, relay or switch, and other specialized inputs. Outputs for

signal conditioning equipment can be voltage, current, frequency, timer or counter,

relay, resistance or potentiometer, and other specialized outputs.

Signal conditioning processes

Signal conditioning can include amplification, filtering, converting, range

matching, isolation and any other processes required to make sensor output suitable

for processing after conditioning.

Filtering

Filtering is the most common signal conditioning function, as usually not all

the signal frequency spectrum contains valid data. The common example are 60Hz

AC power lines, present in most environments, which will produce noise if amplified.

Amplifying

Signal amplification performs two important functions: increases the resolution

of the inputed signal, and increases its signal-to-noise ratio. For example, the output of

an electronic temperature sensor, which is probably in the millivolts range is probably

too low for an Analog-to-digital converter (ADC) to process directly. In this case it isnecessary to bring the voltage level up to that required by the ADC.



Commonly used amplifiers on signal conditioning include Sample and hold

amplifiers, Peak Detectors, Log amplifiers, Antilog amplifiers, Instrumentation

amplifiers or programmable gain amplifiers.

Isolation

Signal isolation must be used in order to pass the signal from the source to the

measurement device without a physical connection: it is often used to isolate possible

sources of signal perturbations. Also notable is that's it is important to isolate the

potentially expensive equipment used to process the signal after conditioning from the

sensor.

Magnetic or optic isolation can be used. Magnetic isolation transforms the signal from

voltage to a magnetic field, allowing the signal to be transmitted without a physical

connection (for example, using a transformer). Optic isolation takes an electronic

signal and modulates it to a signal coded by light transmission (optical encoding),

which is then used for input for the next stage of processing.

Applications

It is primarily utilized for data acquisition, in which sensor signals must be normalized

and filtered to levels suitable for analog-to-digital conversion so they can be read by

computerized devices. Other uses include preprocessing signals in order to reduce

computing time, converting ranged data to boolean values, for example when knowing

when a sensor has reached certain value.

Types of devices that use signal conditioning include signal filters, instrument

amplifiers, sample-and-hold amplifiers, isolation amplifiers, signal isolators,

multiplexers, bridge conditioners, analog-to-digital converters, digital-to-analog

converters, frequency converters or translators, voltage converters or inverters,

frequency-to-voltage converters, voltage-to-frequency converters, current-to-voltage

converters, current loop converters, and charge converters.

\



POWER SUPPLY UNIT

As we all know any invention of latest technology cannot be activated without the

source of power. So it this fast moving world we deliberately need a proper power

source which will be apt for a particular requirement. All the electronic components

starting from diode to Intel IC¶s only work with a DC supply ranging from +5v to

+12. We are utilizing for the same, the most cheapest and commonly available energy

source of 230v-50Hz and stepping down , rectifying, filtering and regulating the

voltage. This will be dealt briefly in the forth-coming sections.

3.1. STEP DOWN TRANSFORMER:When AC is applied to the primary winding of the power transformer it can

either be stepped down or up depending on the value of DC needed. In our circuit the

transformer of 230v/15-0-15v is used to perform the step down operation where a

230V AC appears as 15V AC across the secondary winding . One alteration of input

causes the top of the transformer to be positive and the bottom negative. The next

alteration will temporarily cause the reverse. The current rating of the transformer

used in our project is 2A. Apart from stepping down AC voltages, it gives isolation

between the power source and power supply circuitries.

3.2. RECTIFIER UNIT:

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In the power supply unit, rectification is normally achieved using a solid state

diode. Diode has the property that will let the electron flow easily in one direction at

proper biasing condition . As AC is applied to the diode, electrons only flow when the

anode and cathode is negative. Reversing the polarity of voltage will not permit

electron flow.

A commonly used circuit for supplying large amounts of DC power is the

bridge rectifier. A bridge rectifier of four diodes (4*IN4007) are used to achieve full

wave rectification. Two diodes will conduct during the negative cycle and the other

two will conduct during the positive half cycle. The DC voltage appearing across the

output terminals of the bridge rectifier will be somewhat lass than 90% of the applied

rms value. Normally one alteration of the input voltage will reverse the polarities.Opposite ends of the transformer will therefore always be 180 deg out of phase with

each other.

For a positive cycle, two diodes are connected to the posi tive voltage at the top

winding and only one diode conducts . At the same time one of the other two diodes

conducts for the negative voltage that is applied from the bottom winding due to the

forward bias for that diode. In this circuit due to positive half cycleD1 & D2 will

conduct to give 10.8v pulsating DC. The DC output has a ripple frequency of 100Hz.

Since each altercation produces a resulting output pulse, frequency = 2*50 Hz. The

output obtained is not a pure DC and therefore filtration has to be done.

3.3. FILTERING UNIT:

Filter circuits which is usually a capacitor acting as a surge arrester always

follow the rectifier unit. This capacitor is also called as a decoupling capacitor or a

bypassing capacitor, is used not only to µshort¶ the ripple with frequency of 120Hz to

ground but also to leave the frequency of the DC to appear at the output. A load

resistor R1 is connected so that a reference to the ground is maintained . C1R1 is for bypassing ripples. C2R2 is used as a low pass filter, i.e. it passes only low frequency

signals and bypasses high frequency signals. The load resistor should be 1% to 2.5%

of the load.



1000w

f/25v : for the reduction of ripples from the pulsating.

10wf/25v : for maintaining the stability of the voltage at the load side.

O,1wf : for bypassing the high frequency disturbances.

3.4. VOLTAGE REGULATORS:

The voltage regulators play an important role in any power supply unit. The

primary purpose of a regulator is to aid the rectifier and filter circuit in providing a

constant DC voltage to the device. Power supplies without regulators have an inherent

problem of changing DC voltage values due to variations in the load or due to

fluctuations in the AC liner voltage. With a regulator connected to the DC output, the

voltage can be maintained within a close tolerant region of the desired output. IC7812

and 7912 is used in this project for providing +12v and ±12v DC supply.

3.5. SPECIFICATIONS :

Resistors R1 and R2 maintain line load regulation.

At the secondary side of the transformer,

Applied voltage = 15v

Conducting drop across the diodes = 2*0.6 = 1.2v

Without capacitor:

Vavg = (15-1.2)v = 13.8c pulsating DC Frequency = 100Hz

With capacitor:

V=Vavg *1.414(formfactor)



= 19.51v

frequency = oHz

With 7812 voltage regulator :

V0= +12v

With 7912 voltage regulator :

V0= -12v



PI

Micrcontroller:

PI

16f877 Pin Diagram:

The Microcontroller has many more reasons to be used than the

microprocessors. The difference between the Microprocessors and Microcontrollers

are given below.



Difference between Microprocessors and Microcontrollers

MICROPROCEESOR MICROCONTROLLER

1. No memory Got Separate ROM and RAM

2. No I/O Ports In built Ports Available

3. No Timers Internal Timers Available

4. No Serial Port In built Serial Communication

5. Von Neumann Architecture Harvard Architecture

Other than the normal Microcontrollers PIC Family supports more features, so

we have chosen PIC 16F877 as the main controller. The Main Features and

Peripherals are discussed below.

5.1.

ore Features:

� High performance RISC CPU

� Only 35 single word instructions to learn

� All single cycle instructions except for program Branches which are two cycle

� Operating speed: DC - 20 MHz clock input

DC - 200 ns instruction cycle

� Up to 8�

x 14 words of FLASH Program Memory,

Up to 368 x 8 bytes of Data Memory (RAM)

� Interrupt capability (up to 14 sources)

� Direct, indirect and relative addressing modes



� Power-on Reset (POR)

� Power-up Timer (PWRT) and

Oscillator Start-up Timer (OST)

� Processor read/write access to program memory

� Wide operating voltage range: 2.0V to 5.5V

� Low-power consumption:

- < 0.6 mA typical @ 3V, 4 MHz

- < 1 � A typical standby current

5.2. Peripheral Features:

� Timer0: 8-bit timer/counter with 8-bit prescaler

� Timer1: 16-bit timer/counter with prescaler, can be incremented during SLEEP

� Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler

� 10-bit multi-channel Analog-to-Digital converter

� Synchronous Serial Port (SSP) with SPI (Master mode) and 12C(Master/Slave)

� Universal Synchronous Asynchronous Receiver Transmitter (USART/SCI) with 9-

bit address detection

� Parallel Slave Port (PSP) 8-bits wide, with external RD, WR and CS controls (40/44-

pin only)

5.3. DEVI�

E OVERVIEW

This document contains device specific information. Additional information

may be found in the PICmicro� Mid-Range Reference Manual (DS33023). There



are four devices (PIC16F873, PIC16F874, PIC16F876 and PIC16F877) covered by

this data

sheet. The PIC16F877/874 devices come in 40-pin packages. The Parallel Slave Port

is not implemented on the 28-pin devices. The PIC16F877 Block diagram is shown

below:



PINOUT DES�

RIPTION:

INTERNAL ARCHITECTURE



5.4. I/O PORTS:

Some pins for these I/O ports are multiplexed with an alternate function for the

Peripheral features on the device. In general, when a peripheral is enabled, that pin

may not be used as a general purpose I/O pin.



PORTA and the TRISA Register:

PORTA is a 6-bit wide, bi-directional port. The corresponding data

direction register is TRISA. Setting a TRISA bit (= 1) will make the corresponding

PORTA pin an input (i.e., put the corresponding output driver in a Hi-Impedance

mode). Clearing a TRISA bit (= 0) will make the corresponding PORTA pin an output

(i.e., put the contents of the output latch on the selected pin). Reading the PORTA

register reads the status of the pins, where as writing to it will write to the port latch.

All write operations are read-modify-write operations.Therefore, a write to a port

implies that the port pins are read, the value is modified and then written to the port

data latch. Pin RA4 is multiplexed with the Timer0 module clock input to become the

RA4/T0C�

I pin. All other PORTA pins have TTL input levels and full CMOS output

drivers. Other PORTA pins are multiplexed with analog inputs and analog VREF

input. The operation of each pin is selected by clearing/setting the control bits in the

ADCON1 register (A/D Control Register1).

PORTB and the TRISB Register

PORTB is an 8-bit wide, bi-directional port. The corresponding

data direction register is TRISB. Setting a TRISB bit (= 1) will make the

corresponding PORTB pin an input (i.e., put the corresponding output driver in a Hi-Impedance mode). Clearing a TRISB bit (= 0) will make the corresponding PORTB

pin an output (i.e., put the contents of the output latch on the selected pin). Three pins

of PORTB are multiplexed with the Low Voltage Programming function: RB3/PGM,

RB6/PGC and RB7/PGD. PORTB pins has a weak internal pull-up.

A single control bit can turn on all the pull-ups. This is performed

by clearing bit RBPU (OPTION_REG<7>). The weak pull-up is automatically turned

off when the port pin is configured as an output. The pull-ups are disabled on a

Power-on Reset. This interrupt can wake the device from SLEEP. The user, in the

Interrupt Service Routine, can clear the interrupt in the following manner: a) Any read

or write of PORTB. This will end the mismatch condition. b) Clear flag bit RBIF.A



mismatch condition will continue to set flag bit RBIF. Reading PORTB will end the

mismatch condition and allow flag bit RBIF to be cleared.

The interrupt-on-change feature is recommended for wake-up on

key depression operation and operations where PORTB is only used for the interrupt-

on-change feature. Polling of PORTB is not recommended while using the interrupt-

on-change feature. This interrupt-on-mismatch feature, together with software

onfigureable pull-ups on these four pins, allow easy interface to a keypad and make it

possible for wake-up on key depression. Refer to the Embedded Control Handbook,

³Implementing W � k e-up on K ey S tr ok es´ (AN552). RB0/INT is an external interrupt

input pin and is configured using the INTEDG bit (OPTION_REG<6>).

PORT

and the TRIS

Register:

PORTC is an 8-bit wide, bi-directional port. The corresponding data

direction register is TRISC. Setting a TRISC bit (= 1) will make the corresponding

PORTC pin an input (i.e., put the corresponding output driver in a Hi-Impedance

mode). Clearing a TRISC bit (= 0) will make the corresponding PORTC pin an output

(i.e., put the contents of the output latch on the selected pin). PORTC is multiplexed

with several peripheral functions.

When enabling peripheral functions, care should be taken in defining

TRIS bits for each PORTC pin. Some peripherals override the TRIS bit to make a pin

an output,while other peripherals override the TRIS bit to make a pin an input. Since

the TRIS bit override is in effect while the peripheral is enabled, read-modify write

instructions (BSF, BCF, XORWF) with TRISC as destination, should be avoided. The

user should refer to the corresponding peripheral section for the correct TRIS bit

settings.

PORTD and TRISD Registers:

PORTD is an 8-bit port with Schmitt Trigger input buffers.Each pin

is individually configureable as an input or output.PORTD can be configured as an 8-



bit wide microprocessor port (parallel slave port) by setting control bit PSPMODE

(TRISE<4>). In this mode, the input buffers are TT L.

PORTE and TRISE Register:

PORTE has three pins (RE0/RD/AN5, RE1/WR/AN6,and

RE2/CS/AN7) which are individually configureable as inputs or outputs. These pins

have Schmitt Trigger input buffers.The PORTE pins become the I/O control inputs for

the microprocessor port when bit PSPMODE (TRISE<4>) is set. In this mode, the

user must make certain that the TRISE<2:0> bits are set, and that the pins are

configured as digital inputs. Also ensure that ADCON1 is configured for digital I/O.

In this mode, the input buffers are TTL.

5.5. ADDRESSABLE UNIVERSAL SYN

HRONOUS ASYN

HRONOUS

RE

EIVER

TRANSMITTER (USART):

The Universal Synchronous Asynchronous Receiver Transmitter

(USART) module is one of the two serial I/O modules. (USART is also known as a

Serial Communications Interface or SCI.) The USART can be configured as a full

duplex asynchronous system that can communicate with peripheral devices such as

CRT terminals and personal computers, or it can be configured as a half duplex

synchronous system that can communicate with peripheral devices such as A/D or

D/A integrated circuits, serial EEPROMs etc. The USART can be configured in the

following modes:

� Asynchronous (full duplex)

� Synchronous - Master (half duplex)

� Synchronous - Slave (half duplex)



Bit SPEN (RCSTA<7>) and bits TRISC<7:6> have to be set in order

to configure pins RC6/TX/C

and RC7/RX/DT as the Universal Synchronous

Asynchronous Receiver Transmitter.The USART module also has a multi-processor

communication capability using 9-bit address detection.

TXSTA: TRANSMIT STATUS AND CONTROL REGISTER (ADDRESS 98h)

bit 7 CSR C: Clock Source Select bit

Asynchronous mode: Don¶t care

Synchronous mode:

1 = Master mode (clock generated internally from BRG)

0 = Slave mode (clock from external source)

bit 6 TX9: 9-bit Transmit Enable bit

1 = Selects 9-bit transmission

0 = Selects 8-bit transmission

bit 5 TXEN: Transmit Enable bit

1 = Transmit enabled

0 = Transmit disabled

bit 4 SYNC: USART Mode Select bit

1 = Synchronous mode

0 = Asynchronous mode

bit 2 BRGH: High Baud Rate Select bit



Asynchronous mode:

1 = High speed

0 = Low speed

Synchronous mode: Unused in this mode

bit 1 TRMT: Transmit Shift Register Status bit

1 = TSR empty

0 = TSR full

bit 0 TX9D: 9th bit of Transmit Data, can be parity bit

RCSTA: RECEIVE STATUS AND CONTROL REGISTER (ADDRESS 18h)

bit 7 SPEN: Serial Port Enable bit

1 = Serial port enabled (configures RC7/RX/DT and RC6/TX/C

pins as serial port

pins)

0 = Serial port disabled

bit 6 RX9: 9-bit Receive Enable bit

1 = Selects 9-bit reception

0 = Selects 8-bit reception

bit 5 SREN: Single Receive Enable bit

Asynchronous mode: Don¶t care

Synchronous mode - master:

1 = Enables single receive



0 = Disables single receive

This bit is cleared after reception is complete.

Synchronous mode - slave: Don¶t care

bit 4 CREN: Continuous Receive Enable bit

Asynchronous mode:

1 = Enables continuous receive

0 = Disables continuous receive

Synchronous mode:

1 = Enables continuous receive until enable bit CREN is cleared (CREN overrides

SREN)

0 = Disables continuous receive

bit 2 FERR : Framing Error bit

1 = Framing error (can be updated by reading RCREG register and receive next valid

byte)

0 = No framing error

bit 1 OERR : Overrun Error bit

1 = Overrun error (can be cleared by clearing bit CREN)

0 = No overrun error

bit 0 RX9D: 9th bit of Received Data (can be parity bit, but must be calculated by

user firmware)

USART Baud Rate Generator(BRG):

The BRG supports both the Asynchronous and Synchronous modes

of the USART. It is a dedicated 8-bit baud rate generator. The SPBRG register



controls the period of a free running 8-bit timer. In Asynchronous mode, bit BRGH

(TXSTA<2>) also controls the baud rate.Table shows the formula for computation of

the baud rate for different USART modes which only apply in Master mode (internal

clock). Given the desired baud rate and FOSC, the nearest integer value for the

SPBRG register can be calculated using the formula in Table. From this, the error in

baud rate can be determined. It may be advantageous to use the high baud rate (BRGH

= 1), even for slower baud clocks. This is because the FOSC/(16(X + 1)) equation can

reduce the baud rate error in some cases.Writing a new value to the SPBRG register

causes the BRG timer to be reset (or cleared). This ensures the BRG does not wait for

a timer overflow before outputting the new baud rate.

BAUD RATES FOR ASYNCHRONOUS MODE (BRGH = 0)

BAUD RATES FOR ASYNCHRONOUS MODE (BRGH = 1)



USART Asynchronous Mode:

In this mode, the USART uses standard non-return-to zero (NRZ) format

(one START bit, eight or nine data bits, and one STOP bit). The most common data

format is 8-bits. An on-chip, dedicated, 8-bit baud rate generator can be used to derive

standard baud rate frequencies from the oscillator. The USART transmits and receives

the LSb first. The transmitter and receiver are functionally independent, but use the

same data format and baud rate. The baud rate generator produces a clock, either x16

or x64 of the bit shift rate, depending on bit BRGH (TXSTA<2>). Parity is not

supported by the hardware, but can be implemented in software (and stored as the

ninth data bit).

Asynchronous mode is stopped during SLEEP. Asynchronous mode

is selected by clearing bit SYNC (TXSTA<4>). The USART Asynchronous module

consists of the following important elements:

� Baud Rate Generator

� Sampling Circuit

� Asynchronous Transmitter

� Asynchronous Receiver

USART ASYNCHRONOUS TRANSMITTER:

The heart of the transmitter is the transmit (serial) shift register (TSR). The

shift register obtains its data from the read/write transmit buffer, TXREG. The

TXREG register is loaded with data in software. The TSR register is not loaded until

the STOP bit has been transmitted from the previous load. As soon as the STOP bit is

transmitted, the TSR is loaded with new data from the TXREG register (if available).

Once the TXREG register transfers the data to the TSR register (occurs in one TCY),

the TXREG register is empty and flag bit TXIF (PIR1<4>) is set. This interrupt can be

enabled/disabled by setting/clearing enable bit TXIE ( PIE1<4>). Flag bit TXIF will

be set, regardless of the state of enable bit TXIE and cannot be cleared in software. It



will reset only when new data is loaded into the TXREG register. While flag bit TXIF

indicates the status of the TXREG register, another bit TRMT (TXSTA<1>) shows

the status of the TSR register.

Status bit TRMT is a read only bit, which is set when the TSR

register is empty. No interrupt logic is tied to this bit, so the user has to poll this bit in

order to determine if the TSR register is empty.Transmission is enabled by setting

enable bit TXEN (TXSTA<5>). The actual transmission will not occur until the

TXREG register has been loaded with data and the baud rate generator (BRG) has

produced a shift clock. The transmission can also be started by first loading the

TXREG register and then setting enable bit TXEN. Normally, when transmission is

first started, the TSR register is empty. At that point, transfer to the TXREG register

will result in an immediate transfer to TSR, resulting in an empty TXREG. A back-

to-back transfer is thus possible Clearing enable bit TXEN during a transmission will

cause the transmission to be aborted and will reset the transmitter.

As a result, the RC6/TX/C

pin will revert to hi-impedance.In order

to select 9-bit transmission, transmit bit TX9 (TXSTA<6>) should be set and the ninth

bit should be written to TX9D (TXSTA<0>). The ninth bit must be written before

writing the 8-bit data to the TXREG register. This is because a data write to the

TXREG register can result in an immediate transfer of the data to the TSR register (if

the TSR is empty). In such a case, an incorrect ninth data bit may be loaded in the

TSR register.

When setting up an Asynchronous Transmission, follow these steps:

1. Initialize the SPBRG register for the appropriate baud rate. If a high speed

baud rate is desired, set bit BRGH.

2. Enable the asynchronous serial port by clearing bit SYNC and setting bit

SPEN.

3. If interrupts are desired, then set enable bit TXIE.

4. If 9-bit transmission is desired, then set transmit bit TX9.



5. Enable the transmission by setting bit TXEN, which will also set bit TXIF.

6. If 9-bit transmission is selected, the ninth bit should be loaded in bit TX9D.

7. Load data to the TXREG register (starts transmission).

8. If using interrupts, ensure that GIE and PEIE (bits 7 and 6) of the INTCON

register are set.

USART ASYNCHRONOUS RECEIVER:

The data is received on the RC7/RX/DT pin and drives the data

recovery block. The data recovery block is actually a high speed shifter, operating atx16 times the baud rate; whereas, the main receive serial shifter operates at the bit rate

or at FOSC. Once Asynchronous mode is selected, reception is enabled by setting bit

CREN (RCSTA<4>). The heart of the receiver is the receive (serial) shift register

(RSR). After sampling the STOP bit, the received data in the RSR is transferred to the

RCREG register (if it is empty). If the transfer is complete, flag bit RCIF (PIR1<5>) is

set. The actual interrupt can be enabled/disabled by setting/clearing enable bit RCIE

(PIE1<5>). Flag bit RCIF is a read only bit, which is cleared by the hardware. It is

cleared when the RCREG register has been read and is empty.

If the RCREG register is still full, the overrun error bit OERR

(RCSTA<1>) will be set. The word in the RSR will be lost. The RCREG register can

be read twice to retrieve the two bytes in the FIFO. Overrun bit OERR has to be

cleared in software.This is done by resetting the receive logic (CREN is cleared and

then set). If bit OERR is set, transfers from the RSR register to the RCREG register

are inhibited, and no further data will be received. It is therefore,essential to clear

error bit OERR if it is set. Framing error bit FERR (RCSTA<2>) is set if a STOP bit

is detected as clear. Bit FERR and the 9th receive bit are buffered the same way as the

receive data. Reading the RCREG will load bits RX9D and FERR with new values,therefore, it is essential for the user to read the RCSTA register before reading the

RCREG register in order not to lose the old FERR and RX9D information.



ANALOG-TO-DIGITAL CONVERTER (A/D) MODULE:

The Analog-to-Digital (A/D) Converter module has five inputs for

the 28-pin devices and eight for the other devices. The A/D conversion of the analog

input signal results in a corresponding 10-bit digital number. The A/D converter has a

unique feature of being able to operate while the device is in SLEEP mode. To operate

in SLEEP, the A/D clock must be derived from the A/D¶s internal RC oscillator.The

A/D module has four registers. These registers are:

� A/D Result High Register (ADRESH)

� A/D Result Low Register (ADRESL)

� A/D Control Register0 (ADCON0)

� A/D Control Register1 (ADCON1)

The ADCON0 register, shown in Register 11-1, controls the operation of

the A/D module. The ADCON1 register, shown in Register 11-2, configures the

functions

of the port pins. The port pins can be configured as analog inputs (RA3 can also be the

voltage reference), or as digital I/O.Additional information on using the A/D module

can be found in the PICmicro� Mid-Range MCU Family Reference Manual

(DS33023).

REGISTER 11-1: ADCON0 REGISTER (ADDRESS: 1Fh)

bit 7-6 ADCS1:ADCS0: A/D Conversion Clock Select bits

00 = FOSC/2

01 = FOSC/8



10 = FOSC/32

11 = FRC (clock derived from the internal A/D module RC oscillator)

bit 5-3 CHS2:CHS0: Analog Channel Select bits

000 = channel 0, (RA0/AN0)





101 = channel 5, (RE0/AN5)(1)

110 = channel 6, (RE1/AN6)(1)

111 = channel 7, (RE2/AN7)(1)

bit 2 GO/DONE: A/D Conversion Status bit

If ADON = 1:

1 = A/D conversion in progress (setting this bit starts the A/D conversion)

0 = A/D conversion not in progress (this bit is automatically cleared by hardware

when the A/D conversion is complete)

bit 1 Unimplemented: Read as '0'

bit 0 ADON: A/D On bit

1 = A/D converter module is operating

0 = A/D converter module is shut-off and consumes no operating current

REGISTER 11-2: ADCON1 REGISTER (ADDRESS 9Fh)



bit 7 ADFM: A/D Result Format Select bit

1 = Right justified. 6 Most Significant bits of ADRESH are read as µ0¶.

0 = Left justified. 6 Least Significant bits of ADRESL are read as µ0¶.

bit 6-4 Unimplemented: Read as '0'

bit 3-0 PCFG3:PCFG0: A/D Port Configuration Control bits:

These steps should be followed for doing an A/D Conversion:

1. Configure the A/D module:

� Configure analog pins/voltage reference and digital I/O (ADCON1)

� Select A/D input channel (ADCON0)

� Select A/D conversion clock (ADCON0)

� Turn on A/D module (ADCON0)

2. Configure A/D interrupt (if desired):

� Clear ADIF bit

� Set ADIE bit

� Set PEIE bit

� Set GIE bit

3. Wait the required acquisition time.



4. Start conversion:

� Set GO/DONE bit (ADCON0)

5. Wait for A/D conversion to complete, by either:

� Polling for the GO/DONE bit to be cleared (with interrupts enabled); OR

� Waiting for the A/D interrupt

6. Read A/D result register pair (ADRESH:ADRESL), clear bit ADIF if required.

7. For the next conversion, go to step 1 or step 2, as required. The A/D conversion

time per bit is defined as TAD. A minimum wait of 2TAD is required before the nextacquisition starts.

RESET:

The PIC16F87X differentiates between various kinds of

RESET:

� Power-on Reset (POR)

� MCLR Reset during normal operation

� MCLR Reset during SLEEP

� WDT Reset (during normal operation)

� WDT Wake-up (during SLEEP)

� Brown-out Reset (BOR)

Some registers are not affected in any RESET condition. Their status is unknown on

POR and unchanged in any other RESET. Most other registers are reset to a ³RESET

state´ on Power-on Reset (POR), during SLEEP,

INTERRUPTS:



The PIC16F87X family has up to 14 sources of interrupt.The

interrupt control register (INTCON) records individual interrupt requests in flag bits.

It also has individual and global interrupt enable bits.A global interrupt enable bit,

GIE (INTCON<7>) enables (if set) all unmasked interrupts, or disables (if cleared) all

interrupts. When bit GIE is enabled, and an interrupt¶s flag bit and mask bit are set,

the interrupt will vector immediately. Individual interrupts can be disabled through

their corresponding enable bits in various registers. Individual interrupt bits are

set,regardless of the status of the GIE bit.

The GIE bit is cleared on RESET.The ³return from interrupt´

instruction, RETFIE, exits the interrupt routine, as well as sets the GIE bit, which re-

enables interrupts.The RB0/INT pin interrupt, the RB port change interrupt,and the

TMR0 overflow interrupt flags are contained in the INTCON register.The peripheral

interrupt flags are contained in the special function registers, PIR1 and PIR2. The

corresponding

interrupt enable bits are contained in special function registers, PIE1 and PIE2, and

the peripheral interrupt enable bit is contained in special function register INTCON.

When an interrupt is responded to, the GIE bit is cleared to disable any further

interrupt, the return address is pushed onto the stack and the PC is loaded with 0004h.

Once in the Interrupt Service Routine, the source(s) of the interrupt

can be determined by polling the interrupt flag bits. The interrupt flag bit(s) must be

cleared in software before re-enabling interrupts to avoid recursive interrupts. For

external interrupt events, such as the INT pin or PORTB change interrupt, the

interrupt latency will be three or four instruction cycles. The exact latency depends

when the interrupt event occurs. The latency is the same for one or two-cycle

instructions. Individual interrupt flag bits are set, regardless of the status of their

corresponding mask bit, PEIE bit, or GIE bit.

Note: Individual interrupt flag bits are set, regardless of the status of their

corresponding



mask bit, or the GIE bit.

5.7. INSTRUCTION SET SUMMAR Y:

Each PIC16F87X instruction is a 14-bit word, divided into an OPCODE

which specifies the instruction type and one or more operands which further specify

the operation of the instruction. The PIC16F87X instruction set summary in byte-

oriented, bit-oriented,and literal and control operations. The below Table shows the

opcode field descriptions.

For byte-oriented instructions, ¶f¶ represents a file register designator and

¶d¶ represents a destination designator.The file register designator specifies which file

register is to be used by the instruction.The destination designator specifies where the

result of the operation is to be placed. If ¶d¶ is zero, the result is placed in the W

register. If ¶d¶ is one, the result is placed in the file register specified in the instruction.

For bit-oriented instructions, ¶b¶ represents a bit field designator which

selects the number of the bit affected by the operation, while ¶f¶ represents the address

of the file in which the bit is located.

For literal and control operations, ¶k¶ represents an eight or eleven bit

constant or literal value. All instructions are executed within one single instruction

cycle, unless a conditional test is true or the program counter is changed as a result of

an instruction.In this case, the execution takes two instruction cycles with the second

cycle executed as a NOP. One instruction cycle consists of four oscillator periods.

Thus, for an oscillator frequency of 4 MHz, the normal instruction execution time is 1

s. If a conditional test is true, or the program counter is changed as a result of an

instruction, the instruction execution time is 2

s.



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.



The diagram below shows how the relay is used in circuits such as the sound operated

switch.

Circuit:

Basic design and operation



Simple electromechanical relay

Small relay as used in electronics

A simple electromagnetic relay consists of a coil of wire surrounding a soft

iron core, an iron yoke which provides a low reluctance path for magnetic flux, a

movable iron armature, and one or more sets of contacts (there are two in the relay

pictured). The armature is hinged to the yoke and mechanically linked to one or more

sets of moving contacts. It is held in place by a spring so that when the relay is de-

energized there is an air gap in the magnetic circuit. In this condition, one of the two

sets of contacts in the relay pictured is closed, and the other set is open. Other relays

may have more or fewer sets of contacts depending on their function. The relay in the

picture also has a wire connecting the armature to the yoke. This ensures continuity of

the circuit between the moving contacts on the armature, and the circuit track on the

printed circuit board (PCB) via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil it generates a magnetic field that

attracts the armature, and the consequent movement of the movable contact(s) either

makes or breaks (depending upon construction) a connection with a fixed contact. If

the set of contacts was closed when the relay was de-energized, then the movement

opens the contacts and breaks the connection, and vice versa if the contacts were open.

When the current to the coil is switched off, the armature is returned by a force,

approximately half as strong as the magnetic force, to its relaxed position. Usually this



force is provided by a spring, but gravity is also used commonly in industrial motor

starters. Most relays are manufactured to operate quickly. In a low-voltage application

this reduces noise; in a high voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed across the coil

to dissipate the energy from the collapsing magnetic field at deactivation, which

would otherwise generate a voltage spike dangerous to semiconductor circuit

components. Some automotive relays include a diode inside the relay case.

Alternatively, a contact protection network consisting of a capacitor and resistor in

series (snubber circuit) may absorb the surge. If the coil is designed to be energized

with alternating current (AC), a small copper "shading ring" can be crimped to the end

of the solenoid, creating a small out-of-phase current which increases the minimum

pull on the armature during the AC cycle.[1]

A solid-state relay uses a thyristor or other solid-state switching device, activated by

the control signal, to switch the controlled load, instead of a solenoid. An optocoupler

(a light-emitting diode (LED) coupled with a photo transistor) can be used to isolate

control and controlled circuits.

Types

Latching relay

Latching relay with permanent magnet

A latching relay has two relaxed states (bistable). These are also called

"impulse", "keep", or "stay" relays. When the current is switched off, the relay



r ª « ¬ i s i its l¬ st st¬ tª .®

̄

is is ¬ °

̄

iª ved ± it ̄

¬ s² lenoid oper ¬ ting ¬ r ¬ t°

̄

et ¬ nd ° ¬ « « echanis« , or

³

́ having t± o opposing coils ± ith an over -center spring or per « anent«

agnet to hold the ar « atµ r e and contacts in position ± hile the coil is r elaxed, or ± ith

a r emanent cor e. In the r atchet and cam example, the first pulse to the coil tur ns the

r elay on and the second pulse tur ns it off. In the t± o coil exa mple, a pulse to one coil

tur ns the r elay on and a pulse to the opposite coil tur ns the r elay off.®

his type of r elay

has the advantage that one coil consumes power only f or an instant, while it is³

eing

switched, and the r elay contacts r etain this setting acr oss a power outage. A r emanent

cor e latching r elay r equir es a curr ent pulse of opposite polarity to make it change

state.

¶

eed r elay

A r eed r elay is a r eed switch enclosed in a solenoid.®

he switch has a set of contacts

inside an evacuated or inert gas-filled glass tube which pr otects the contacts against

atmospheric corr osion; the contacts ar e made of magnetic material that makes them

move under the influence of the field of the enclosin g solenoid.¶

eed r elays can

switch f aster than lar ger r elays, r equir e only little power fr om the contr ol cir cuit, but

have low switching curr ent and voltage r atings.

®

op, middle: r eed switches, bottom: r eed r elay

·

er cur y-wetted r elay

A mer cur y-wetted r eed r elay is a f or m of r eed r elay in which the contacts ar e wetted

with mer cur y. Such r elays ar e used to switch low -voltage signals (one volt or less)



often used for motor starters. A motor starter is a contactor with overload protection

devices attached. The overload sensing devices are a form of heat operated relay

where a coil heats a bi-metal strip, or where a solder pot melts, releasing a spring to

operate auxiliary contacts. These auxiliary contacts are in series with the coil. If the

overload senses excess current in the load, the coil is de-energized. Contactor relays

can be extremely loud to operate, making them unfit for use where noise is a chief

concern.

Solid-state relay

Solid state relay, which has no moving parts

25 A or 40 A solid state contactors

A solid state relay (SSR) is a solid state electronic component that provides a

similar function to an electromechanical relay but does not have any moving

components, increasing long-term reliability. With early SSR's, the tradeoff came

from the fact that every transistor has a small voltage drop across it. This voltage drop



limited the amount of current a given SSR could handle. As transistors improved,

higher current SSR's, able to handle 100 to 1,200 Amperes, have become

commercially available. Compared to electromagnetic relays, they may be falsely

triggered by transients.

Solid state contactor relay

A solid state contactor is a heavy-duty solid state relay, including the necessary heat

sink, used for switching electric heaters, small electric motors and lighting loads;

where frequent on/off cycles are required. There are no moving parts to wear out and

there is no contact bounce due to vibration. They are activated by AC control signals

or DC control signals from Programmable logic controller (PLCs), PCs, Transistor-

transistor logic (TTL) sources, or other microprocessor and microcontroller controls.

Buchholz relay

A Buchholz relay is a safety device sensing the accumulation of gas in large oil-filled

transformers, which will alarm on slow accumulation of gas or shut down the

transformer if gas is produced rapidly in the transformer oil.

Forced-guided contacts relay

A forced-guided contacts relay has relay contacts that are mechanically linked

together, so that when the relay coil is energized or de-energized, all of the linked

contacts move together. If one set of contacts in the relay becomes immobilized, no

other contact of the same relay will be able to move. The function of forced-guided

contacts is to enable the safety circuit to check the status of the relay. Forced-guided

contacts are also known as "positive-guided contacts", "captive contacts", "locked

contacts", or "safety relays".

Overload protection relay

Electric motors need overcurrent protection to prevent damage from over-loading the

motor, or to protect against short circuits in connecting cables or internal faults in the



motor windings. [̧ ]

¹

ne type of electric motor overload pr otection r elay is oper ated by

a heating element in series with the electric motor.º

he heat gener ated by the motor

curr ent heats a bimetallic strip or melts solder, r eleasing a spring to oper ate contacts.

Wher e the overload r elay is exposed to the same envir onment as the motor, a usef ul

though cr ude compensation f or motor ambient temper atur e is pr ovided.

Pole and thr ow

»

ir cuit symbols of r elays. (

»

denotes the common ter minal in SP

¼ º

and

¼

P

¼ º

types.)

Since r elays ar e switches, the ter minology applied to switches is also applied to r elays.

A r elay will switch one or mor e poles, each of whose contacts can be thr own by

ener gi½ ing the coil in one of thr ee ways:

y Nor mally-open (NO) contacts connect the cir cuit when the r elay is activated;

the cir cuit is disconnected when the r elay is inactive. It is also called a For m A

contact or "make" contact. NO contacts can also be distinguished as "early -

make" or NOEM, which means that the contacts will close bef or e the button or

switch is f ully engaged.



y Normally-closed (NC) contacts disconnect the circuit when the relay is

activated; the circuit is connected when the relay is inactive. It is also called a

Form B contact or "break" contact. NC contacts can also be distinguished as

"late-break" or NCLB, which means that the contacts will stay closed until the

button or switch is fully disengaged.

y Change-over (CO), or double-throw (DT), contacts control two circuits: one

normally-open contact and one normally-closed contact with a common

terminal. It is also called a Form C contact or "transfer" contact ("break before

make"). If this type of contact utilizes a "make before break" functionality, then

it is called a Form D contact.

The following designations are commonly encountered:

y SPST ± Single Pole Single Throw. These have two terminals which can be

connected or disconnected. Including two for the coil, such a relay has four

terminals in total. It is ambiguous whether the pole is normally open or

normally closed. The terminology "SPNO" and "SPNC" is sometimes used to

resolve the ambiguity.

y SPDT ± Single Pole Double Throw. A common terminal connects to either of

two others. Including two for the coil, such a relay has five terminals in total.

y DPST ± Double Pole Single Throw. These have two pairs of terminals.

Equivalent to two SPST switches or relays actuated by a single coil. Including

two for the coil, such a relay has six terminals in total. The poles may be Form

A or Form B (or one of each).

y DPDT ± Double Pole Double Throw. These have two rows of change-over

terminals. Equivalent to two SPDT switches or relays actuated by a single coil.

Such a relay has eight terminals, including the coil.

The "S" or "D" may be replaced with a number, indicating multiple switches

connected to a single actuator. For example 4PDT indicates a four pole double throw

relay (with 14 terminals).



EN 50005 are among applicable standards for relay terminal numbering; a typical EN

50005-compliant SPDT relay's terminals would be numbered 11, 12, 14, A1 and A2

for the C, NC, NO, and coil connections, respectively.

Applications

Relays are used to and for:

y Control a high-voltage circuit with a low-voltage signal, as in some types of

modems or audio amplifiers,

y Control a high-current circuit with a low-current signal, as in the starter

solenoid of an automobile,y Detect and isolate faults on transmission and distribution lines by opening and

closing circuit breakers (protection relays),

A DPDT AC coil relay with "ice cube" packaging

y Isolate the controlling circuit from the controlled circuit when the two are at

different potentials, for example when controlling a mains-powered device

from a low-voltage switch. The latter is often applied to control office lighting

as the low voltage wires are easily installed in partitions, which may be often

moved as needs change. They may also be controlled by room occupancy

detectors in an effort to conserve energy,y Logic functions. For example, the boolean AND function is realised by

connecting normally open relay contacts in series, the OR function by

connecting normally open contacts in parallel. The change-over or Form C



contacts perform the XOR (exclusive or) function. Similar functions for NAND

and NOR are accomplished using normally closed contacts. The Ladder

programming language is often used for designing relay logic networks.

o Early computing. Before vacuum tubes and transistors, relays were used

as logical elements in digital computers. See ARRA (computer),

Harvard Mark II, Zuse Z2, and Zuse Z3.

o Safety-critical logic. Because relays are much more resistant than

semiconductors to nuclear radiation, they are widely used in safety-

critical logic, such as the control panels of radioactive waste-handling

machinery.

y Time delay functions. Relays can be modified to delay opening or delayclosing a set of contacts. A very short (a fraction of a second) delay would use

a copper disk between the armature and moving blade assembly. Current

flowing in the disk maintains magnetic field for a short time, lengthening

release time. For a slightly longer (up to a minute) delay, a dashpot is used. A

dashpot is a piston filled with fluid that is allowed to escape slowly. The time

period can be varied by increasing or decreasing the flow rate. For longer time

periods, a mechanical clockwork timer is installed.

Buzzers

This buzzer is an electromagnetic type audio signaling device, which has a coil

inside which oscillates a metal plate against another, which when given voltage

difference produces sound of a predefined frequency. You must be aware of such

sounds of buzzer like BEEP sound in many appliances.



Frequency Characteristics

Dimensions



Precautions

Do not make sound on the buzzer when it is close to ears.

Listening to the buzzer when it is close to ears, or continuant listening to it for

an extended period, may result in hearing disorders.

Thoroughly warn consumers not to turn on the sound when the buzzer is close

to ears.

Do not exceed the rated operation voltage range when using the buzzer. If it is

exceeded

beyond the rated operation voltage, a built-in coil may generate heat, resulting

in deterioration of the coil, which may cause a drop in sound pressure or a

change in the terminal resistance value. If a rare short circuit occurs due to heatgenerated in the built-in coil, a large electrical current flows to the equipment

used, possibly causing it to emit smoke or fire.

The buzzer is a magnetic type sounder.

Do not use it for any other purpose than a sound generation.

Do not use the buzzer in other than atmospheric air.

Do not use the buzzer in the following environments (excluding cases in which

counter measures are taken).

Corrosive gases (Cl2, NH3, SOx, NOx, etc.)

Places to be exposed to dust. Places where rain, fog, salt water, and the like will get on the buzzer.

After installing the buzzer when designing an apparatus, confirm that there are

no



abnormalities by performing a reliability evaluation test.

Do not exceed the rated operating temperature range when using the buzzer.

Do not use for an extended period at relative humidity in excess of 90%

(maximum wet-bulb temperature of 38°C).

When using the buzzer for a safety device or warning device, take all surest

measures such as providing a safety circuit or the joint use of another sounder

with equivalent characteristics in order to prevent accidents.

The buzzer may be influenced by electromagnetic waves, voltage changes, and

ripple voltage.

Check the buzzer in the mounted condition, and take measures such as safety

circuits, shielding, etc. If the buzzer is molded or secured by adhesives, thermal expansion stresses from

the mold or adhesive agent may cause deterioration in a soldered terminal part.

Before molding or securing an adhesive, consider the type, amount, hardening

conditions, adhesive properties, etc., of the sealing material, and confirm the

reliability.

Do not apply vibrations or shocks (such as dropping) larger than the specified.

Do not bend the terminal pin when soldering to install on a circuit board.

Do not apply larger than the specified force to the terminal pin.

Do not apply force to the terminal pin at high temperatures (when soldering).

When soldering a terminal pin, perform the soldering in clean conditions without

contamination or rust in order to avoid poor connections. When performing dip

soldering directly for installing on a printed circuit board, be careful so that smoke

from the flux, or other foreign materials, will not get into the sound emission hole.

Do not clean(excluding products that can be cleaned).With regards to devices in

which the consumers can touch the buzzer, thoroughly warn consumers not to put

foreign materials (such as needles, hairpins, garbage, etc.) into the sound emission

hole.

As the buzzer uses a coil, it has an inductive load. Protect the drive circuit by

putting the diodes in parallel into the buzzer.

Do not reconfigure the buzzer.



Sound pressure changes depending on the shape of the part to be installed in a

device, or the installation location.

Check the buzzer in the mounted condition. The buzzer has polarities.

When installing, be careful not to make a mistake with the polarities.

As the buzzer uses a magnet, it generates a surrounding magnetic field.

When designing a device, etc., confirm that there are no irregularities due to the

magnetic field.

The characteristics of the buzzer may change because of the influence of an

outside magnetic field.

Check the buzzer in the mounted condition, and take measures such as shielding,

etc. Because of deterioration or damage, maintain in rated storage temperature range,

avoid environments where there are sudden temperature changes, direct sunlight,

corrosive gases and dust, and store wrapped in order to avoid applying stresses.

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