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EFY Special Isuue Microcontroller based tvnovellas.info - Download as PDF File .pdf ), Text File .txt) or read online. An EFY Group Publication $10 Microcontroller Based Projects Arduino-Based RF Controlled Robot RFID-Based Automatic Vehicle Parking. Download full-text PDF .. Microcontroller-Based Tachometer Security System' published in EFY Electronics Projects Vol. 19 also.
The microcontroller is one of the most popular general-purpose microcontrollers in use. They can be easily programmed using assembly language. Here we look at some interesting microcontroller projects and the MCS family. This project includes basics of interfacing LCD to a microcontroller. More details on microcontroller projects available at: Interfacing LCD with Microcontroller.
Moving message over dot matrix display Intruder alarm LED based message display DC-To-DC converter Versatile proximity dectetor with auto reset Window charger Multiband CW transmitter Programmable timer for appliances Antibag snatching alarm Off timer with alarm Over voltage protector Fuse cum power failure indicator LED based reading lamp Mobile cellphone charger Smart foot switch Doorbell controlled porchlight AC mains voltage indicator Sound operated light Low cost electronic quiz table Zener diode tester Highway alert signal lamp Variable power supply with digital control Simple security system Low resistance continuity tester Clap operated electronic switch Light controlled digital fan regulator Sensitive optical burglar alarm Watchman watcher Panel frequency meter Random flashing X-mas stars PC based DC motor speed controller Frequency divider using decade counter Dome lamp dimmer Offset tuning indicator for CW Stabilised power supply with short circuit indication Light operated internal door latch Mains box heat monitor Digital stop watch Flashing cum running light Faulty car indicator alarm Quality FM transmitter Simple key opertated gate locking system DC motor control using a single switch Handy tester Programmable electronic dice PC based candle ignitor The keypad is also used formodifying the default password as well asrelay-activation time period.
The keypad is arranged in a 3x4 matrix. At 5ms interval, the microcontroller sets one of the four scan lines as low and other three scan lines as high,and then checks for the status of sense lines one by one. If any of the sense lines is found low, it means that a keyat the intersection of a specific scan line and sense line has been pressed.
Similarly, after 5 ms, the next scan line is made low and remaining three scan lines are taken high, andagain all three sense lines are checked for low level.
This way the microcontroller can check whether any of thetwelve keys is pressed. Due to the high speed of the microcontroller, status of different keys is checked in less than ms and a key-press is detected and identified. As the keys are pressed manually by the user, this delay of ms is not noticeable. A single-pole double-throw SPDT relay is connected to pin 9 of the microcontroller through adriver transistor. The relay requires 12 volts at a current of around 50 mA, which cannot be provided by the mi-Fig.
Actual-size, single-side PCB forthe keypadFig. Component layout for the PCB in Fig. So the driver transistor is added. The relay is usedto operate the external solenoid forming part of a locking deviceor for operating any other electrical device. Normally, the relayremains off.
As soon as pin 9 of the microcontroller goes high,the relay operates. The buzzer is connected to pin 8 of the microcon-troller. It beeps to indicate key and password entry. The buzzergives a small beep whenever a key is pressed. In the case ofa wrong password entry the buzzer gives a long beep, and inthe case of a right password entry it gives three short beeps. The buzzer also gives short beeps as long as the relay remainsenergised.
OperationThe complete design is based on two parameters: Both these parameterscan be changed without making any change in the hardware. Flow-chart for the access-control system, continued in Figs 9 b and 9 c Fig. Microcontroller-Based Projects 7user can change theseparameters any num-ber of times usingthe keypad. The flow-charts for changingthe password andrelay-activation timeduration are shown inFigs 3 and 4, respec-tively.
TestingActual-size, single-side PCBs for theaccess control system without keypad andthat of the keypadare shown in Figs 5and 6, respectively,with their compo-nent layouts in Figs7 and 8, respectively. Afterassembling the unit,check various pointswithout inserting theprogrammed micro-controller and memo-ry ICs as follows: Ensure that the input voltage is V DC from an external source.
The outputat pin 3 of the should be 5 volts. Normally, the relaywould remain off. However, when pin 9 of the MCU socket is connected to 5V, the relay should energise. Nor-mally, the buzzer would be off. Flow-chart for the access-control system, continued from Fig. For a higher-value capacitor, the crystal will not work. OperationSwitch off the supply and insert only the microcontroller. Ensure correct direction and correct insertion of allthe pins. Switch on the unit.
On entering default password through the keypad, the relay will operatefor around 10 seconds default time duration. Each key-press gives a short beep. On entering some other code, say, , the relay should not operate and thebuzzer should give a long beep. Change the password and the relay time. Check the operation with new password and relay activation period.
Microcontroller-Based Projects 9Since there is no memory, the new password and relay time entered will be lost as soon as you switch off the unit. The next time you switch on the unit, the password is again set to and the relay time to 10 seconds as defaultparameters. Now insert the memory IC and change the password and the relay-activation time duration.
On changingthe same, the new password and changed relay-activation time are saved in the memory, which will be recalled atthe next power-on. Take care while connecting and using the live V wires. DOS-based programs can also be used for software development.
So if you are comfortable with DOS or havean old computer with limited hard disk capacity, you will still face no difficulty. Program development steps. You can write the software by using the following steps: The help option of the software will clear most of your doubts. You should also have a clear knowledgeof the logic sequence of the end-product operation. For this, you can make a flow-chart. Flow-chart for this accesscontrol system is shown in Figs 9 a - c. The corresponding software source code is given at the end of this article.
Convert the flow-charts to source program in Assembly language making use of the instruction set of themicrocontroller and assembler directives. You can use any text editor for writing the same or use the text editorof the Integrated Development Environment IDE , which also includes assembler, simulator, and programmingsoftware.
The Assembly-level program is to be saved in a file with.
Assemble the source code, i. The object code will be in S19format, i. You can also choose options within the dialogue box togenerate listing file with extension. LST and. MAP file for source-level debugging. During simulation you may find that the program is not behaving properly. Assuming that your hardware isokay, the most probable reason is an error in writing the software.
You should be able to simulate complete functions without using the actual microcontroller chip. Now, program the microcontroller with the developed and tested software. After programming the micro-controller, insert it into the circuit and check all functions again. The MN is attached to reset pin 9 of the microcontroller. If the MN is not available, you canuse only the RC circuit. ASM All relevant files are included in CD. So the code lock can beused as a multiuser code lock, where the users canaccess respective devices by entering the devicenumber followed by the password.
The passwordcan be changed by the user and no external back-up supply is needed to retain the password. Thepassword length for each device can be between 4and 15 digits, as desired by the user. A buzzer has been added to provide suitablefeedback with respect to the data entered via thekeypad. The number of beeps indicates whetherthe data has been entered correctly or not.
When anyone trying to access the device enters the incorrect passwordthree times, the circuit sounds an alarm. The alarm can beconfigured to work intwo modes: In theauto-reset alarm mode,all the keys pressed areignored and the buzzerkeeps beeping continu-ously for one minute,and thereafter the codelock resets automatically.
However, if youwant additional secu-rity, you can enable thelatch-up mode. In thismode the code locknever switches to thenormal mode from thealarm mode and theonly way to reset thecode lock is to interruptthe power.
When not inuse, the code lock goesinto sleep mode, and itWorking model of PIC16Fbased coded device switching systemFig. Block diagram of PIC16Fbased coded device switching system This feature reduces thepower consumption by the microcontroller. The main features of PIC16F84 microcontrollerare: Program and data memory are in separateblocks, with each having its own bus connecting tothe CPU2.
Reduced instruction set controller RISC withonly 35 instructions to learn3. Code protection Built-in power-on-reset, power-up timer, oscillator start-uptimer Power-saving sleep modeCircuit descriptionFig. Basically, the circuit shown in Fig. The microcontroller.
Its internal circuitry reduces the need for external components, thusreducing the cost and power consumption and enhancing the systemreliability. The microcontroller has two ports, namely, Port A andPort B. One can resetthe microcontroller only by interrupting the power. The memorycan be programmed and read by both the device programmer and the CPU when the device is not code protected.
It is non-volatile and can retain data for more than 40 years. The internal oscillator circuitry of the microcontroller generates the device clock.
The microcontrollercan be configured to work in one of the four oscillator modes: External resistor-capacitor2. Low-power crystal oscillation frequency up to kHz 3. R1 - kilo-ohmR2 - 4. Microcontroller-Based Projects 21Reset circuit. The built-in power-on reset cir-cuitry of the microcontroller eliminates the needfor the external power-on reset circuit.
In theFig. The internalpower-up timer PWRT provides a nominal 72msdelay from power-on reset.
This delay allows VDDto rise to an acceptable level when the microcontroller is poweredFig. Component layout for the PCBFig. Flow-chart of the main program Microcontroller-Based Projects 23on. The oscillator start-up timer OST provides oscil-lator cycle delay after the power-up timer delay is over.
Thisensures that the crystal oscillator has started and is stable. Any othersource such as a 12V lead-acid battery can also be used.
This 12V DC is used for operation of the relays used in thecircuit.
Diode D1 protectsthe circuit from reverse supply connections. Capacitor C1filters out the ripples present in the incoming DC voltage. The key matrix keyboard comprises 12 tac-tile pushbutton switches arranged in four rows and three col-umns as shown in Fig. Data is entered via this keyboard. Port Bof IC2 has weak internal pull-ups, which can be enabledthrough the software. This eliminates the need for connect-ing external pull-up resistors to pins 10 through In the scanning routine, initially all the scan lines aremade low and it is checked whether all the keys are in re-leased state.
If all the keys are in released state, the processoris put into sleep power-down mode. When any key is pressed, one of the sense lines becomeslow. This change in the pin status causes an interrupt to wakeup the microcontroller IC2 from sleep.
Now each scan line is made low while keeping the re-maining scan lines in high state. After making a scan linelow, the status of the sense lines is read. If any of the senselines is found low, it means that a key at the intersection ofthe current scan line and the low sense line has been pressed. If no key is found to be pressed, the next scan line is madelow and again scan lines are checked for low state. This wayall the twelve keys are checked for any pressed key by themicrocontroller.
Since mechanical tactile switch keys are used, pressingof a single key may be considered by the microcontroller aspressing of many keys due to the bouncing of the keys. Toavoid this, the processor is made to wait up to a debouncedelay of 20 ms during the pressing or releasing of a key. Within this debounce delay, all the bounces get settled out,thus debouncing the key. In sleep power-down mode, the device oscillator isturned off and the microcontroller is placed in its lowest-current consumption state.
Also note that the mi-Fig. Diodes D2 through D5 are used as freewheel clamp diodes. The buzzergives a short beep when any key is pressed.
In the case of a wrong data entry, the buzzer gives a long beep toindicate the error. On successful password verification, it gives three short beeps, and after successful passwordchange, it gives two short beeps.
When a wrong password is entered consecutively for three times, the buzzersounds an alarm. The main circuit and the matrix keyboard can be assembled on separate PCBs.
First check the assembledFig. Flow-chart for changing the password of the code lock Connectthe external 12VDC supply withthe correct polar-ity, without in-serting the PICmicrocontrollerinto the socket,and follow thesesteps: Now thebuzzer shouldbeep continu-ously.
Before placing jumper JP1, check the voltage at pin 3 of IC2 using a multimeter. Now on placing jumper JP1, the meter should read 0V or logic 0 at pin 3. Now remove the supply and insert the programmed PIC16F84 microcontroller into the socket and switch onthe supply. After power-on, the buzzer beeps once to indicate that the microcontroller is ready to take the userFig.
Flow-chart for password verification,device channel selection and key scanning Now enter the device number by pressing the button corresponding to the device number.
The valid devicenumbers are 1 to 4. For example, if you want to access device No. Now enter your password digits one by one. The buzzer gives three short beeps to indicate successful verification of the password.
If the entered passwordis incorrect, the buzzer gives a long beep to indicate error. To try again, repeat the procedure from step 1. If the entered password is correct, you can unlock or switch on device No. For changing the password: Press the password change button CHG on the keypad.
Now press the device number.
Enter your current password. On successful verification of the password, the buzzer gives three short beeps. If the entered password iswrong, the buzzer will give a long beep.
Now if you want to try again, repeat the procedure from step 1. Enter your new password. The length of the password should be between 4 and 15 digits. End the password entry by pressing again CHG button. Again enter your new password for confirmation.
On successful confirmation, your new password getsreplaced by the old password and the buzzer beeps twice to indicate successful password change.
In case thepassword entered for confirmation is wrong, the buzzer gives a long beep to indicate error and the old passwordremains unaltered. Mode of operation. When anyone fails to enter the correct password in three attempts, the code lock circuitswitches to alarm mode and the buzzer starts beeping continuously.
All the keys pressed for further attempts areignored by the code lock during alarm mode. Whereasremoving the jumper enables the latch-up mode see Fig. If the auto-rest alarm mode is enabled,the code lockautomatically resets after about one minute. If the latch-up alarm mode is enabled,the code lock never resets fromthe alarm mode until the user manually resets it by interrupting the power.