SPEEDO METER RVCE

Depart of CSE 1

MICROCONTROLLER

A microcontroller is a small computer on a single integrated circuit containing a processor

core, memory, and programmable input/output peripherals. Program memory in the form of

NOR flash or OTP ROM is also often included on chip, as well as a typically small amount

of RAM. Microcontrollers are designed for embedded applications, in contrast to the

microprocessors used in personal computers or other general purpose applications.

Microcontrollers are used in automatically controlled products and devices, such as

automobile engine control systems, implantable medical devices, remote controls, office

machines, appliances, power tools, toys and other embedded systems. By reducing the size

and cost compared to a design that uses a separate microprocessor, memory, and input/output

devices, microcontrollers make it economical to digitally control even more devices and

processes. Mixed signal microcontrollers are common, integrating analog components needed

to control non-digital electronic systems.

Some microcontrollers may use four-bit words and operate at clock rate frequencies as low as

4 kHz, for low power consumption (milli watts or microwatts). They will generally have the

ability to retain functionality while waiting for an event such as a button press or other

interrupt; power consumption while sleeping (CPU clock and most peripherals off) may be

just nanowatts, making many of them well suited for long lasting battery applications. Other

microcontrollers may serve performance-critical roles, where they may need to act more like

a digital signal processor (DSP), with higher clock speeds and power consumption

A microcontroller can be considered a self-contained system with a processor, memory and

peripherals and can be used as an embedded system. The majority of microcontrollers in use

SPEEDO METER RVCE

Depart of CSE 2

today are embedded in other machinery, such as automobiles, telephones, appliances, and

peripherals for computer systems. These are called embedded systems. While some

embedded systems are very sophisticated, many have minimal requirements for memory and

program length, with no operating system, and low software complexity.

Typical input and output devices include switches, relays, solenoids, LEDs, small or custom

LCD displays, radio frequency devices, and sensors for data such as temperature, humidity,

light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other

recognizable I/O devices of a personal computer, and may lack human interaction devices of

any kind.

MICROCONTROLLER FEATURES:

1. (It is similar to 8051 microcontroller i.e. having same instruction set, pin

configuration, architecture).

2. It is also 8-bit microcontroller. Its cost is only Rs10 more than that of 8051.

3. It uses EPROM (erasable programmable read only memory) or FLASH memory.

4. It is multiple time programmable (MTP).

The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K

bytes of Flash programmable and erasable read only memory (PEROM). The device is

manufactured using Atmel’s high-density nonvolatile memory technology and is compatible

with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the

program memory to be reprogrammed in-system or by a conventional nonvolatile memory

programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel

AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective

solution to many embedded control applications.

The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of

RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a

full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is

designed with static logic for operation down to zero frequency and supports two software

selectable power saving modes.

The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and

interrupt system to continue functioning. The Power-down Mode saves the RAM contents but

freezes the oscillator disabling all other chip functions until the next hardware reset.

SPEEDO METER RVCE

Depart of CSE 3

How to make a digital speedometer using microcontroller

The 8051 may not be the best for this task, in that you can get types with lower power and

small size (8/16 pin dip etc). That is not the only family, but it is popular with hobbyists so

there are plenty of software examples on the internet. You can use this software as an

example for other microprocessors too. The first decision is selecting a display that suits your

microprocessor and hardware.

The most basic concept is a frequency counter. Use a magnetic pickup from the wheel. This

can be mounted on a spoke. You can use a fixed coil of wire or a hall effect device to detect

the magnet. This can be mounted on a wheel fork, so the spoke passes close by. The coil

voltage will need signal processing, like voltage limiting, an op-amp and filter, to convert to

digital pulses for the Processor input.

You could use an optical method instead, using LED and reflection from spokes.

Count the pulses, it is best to measure period between pulses to avoid having to count for n

seconds to get a meaningful result. A problem to overcome is converting this to speed, as you

will have to implement maths (multiply and divide), or use a lookup table. Use a high level

language like C or basic and you have maths easily. The driving of an LCD display depends

on which type you have. You could look that up on the internet.

For odometer, just count the impulses and totalize them, then multiply by the factor to get

miles, km etc. You may want to add some sort of push button to the I/O to control the

display.

The power supply may be a battery, if the microprocessor uses little power, or if you use the

bike power (whatever it is) it will need attention to protect everything from spikes in voltage.

Good filtering before any regulator.

A pic micro is the way to go. Check out www.microchip.com You should find some ideas

and details in their applications section, and you can even procure a free sample or two of

their controllers on their website.

An easy way of counting the pulses from the wheel that will not affect tire balance might be

to use a photo sensor. A simple infrared led and photo transistor, and you won't need much

circuitry to condition the pulse back to the micro controller.

Depending on the color and reflectivity of your tires rim, you would either attach a small

section of flat black tape or a section of reflective tape to the rim in one spot. The photo

sensor could be set up to either count a pulse of reflected light as a signal or the absence of a

light signal as the count.

Basically count the revolutions of the wheel, calculate the wheel's effective circumference,

and you can compute the distance traveled per pulse. Using the micro controllers oscillator as

a time base, you can calculate the number of pulses per unit of time, and using the distance

traveled per pulse, figure out the speed.

SPEEDO METER RVCE

Depart of CSE 4

LCD interfacing with Microcontrollers tutorial ►Introduction

The most commonly used Character based LCDs are based on Hitachi's HD44780 controller

or other which are compatible with HD44580. In this tutorial, we will discuss about character

based LCDs, their interfacing with various microcontrollers, various interfaces (8-bit/4-bit),

programming, special stuff and tricks you can do with these simple looking LCDs which can

give a new look to your application.

►Pin Description

The most commonly used LCDs found in the market today are 1 Line, 2 Line or 4 Line LCDs

which have only 1 controller and support at most of 80 charachers, whereas LCDs supporting

more than 80 characters make use of 2 HD44780 controllers.

Most LCDs with 1 controller has 14 Pins and LCDs with 2 controller has 16 Pins (two pins

are extra in both for back-light LED connections). Pin description is shown in the table

below.

Figure 1: Character LCD type HD44780 Pin diagram

Pin No. Name Description

Pin no. 1 VSS Power supply (GND)

Pin no. 2 VCC Power supply (+5V)

Pin no. 3 VEE Contrast adjust

Pin no. 4 RS 0=Instruction input

1 = Data input

Pin no. 5 R/W

0 = Write to LCD module

1 = Read from LCD

module

Pin no. 6 EN Enable signal

Pin no. 7 D0 Data bus line 0 (LSB)

Pin no. 8 D1 Data bus line 1

Pin no. 9 D2 Data bus line 2

Pin no. 10 D3 Data bus line 3

Pin no. 11 D4 Data bus line 4

Pin no. 12 D5 Data bus line 5

SPEEDO METER RVCE

Depart of CSE 5

Pin no. 13 D6 Data bus line 6

Pin no. 14 D7 Data bus line 7 (MSB)

Table 1: Character LCD pins with 1 Controller

Pin No. Name Description

Pin no. 1 D7 Data bus line 7 (MSB)

Pin no. 2 D6 Data bus line 6

Pin no. 3 D5 Data bus line 5

Pin no. 4 D4 Data bus line 4

Pin no. 5 D3 Data bus line 3

Pin no. 6 D2 Data bus line 2

Pin no. 7 D1 Data bus line 1

Pin no. 8 D0 Data bus line 0 (LSB)

Pin no. 9 EN1 Enable signal for row 0 and 1 (1stcontroller)

Pin no. 10 R/W 0 = Write to LCD module

1 = Read from LCD module

Pin no. 11 RS 0 = Instruction input

1 = Data input

Pin no. 12 VEE Contrast adjust

Pin no. 13 VSS Power supply (GND)

Pin no. 14 VCC Power supply (+5V)

Pin no. 15 EN2 Enable signal for row 2 and 3 (2nd

controller)

Pin no. 16 NC Not Connected

Table 2: Character LCD pins with 2 Controller

Usually these days you will find single controller LCD modules are used more in the

market. So in the tutorial we will discuss more about the single controller LCD, the operation

and everything else is same for the double controller too. Lets take a look at the basic

information which is there in every LCD.

►Sending Data to LCD

To send data we simply need to select the data register. Everything is same as the command

routine. Following are the steps:

Move data to LCD port

select data register

select write operation

send enable signal

wait for LCD to process the data

Keeping these steps in mind we can write LCD command routine as.

SPEEDO METER RVCE

Depart of CSE 6

CODE:

;Ports used are same as the previous example

;Routine to send data (single character) to LCD

LCD_senddata:

mov LCD_data,A ;Move the command to LCD port

setb LCD_rs ;Selected data register

clr LCD_rw ;We are writing

setb LCD_en ;Enable H->L

clr LCD_en

acall LCD_busy ;Wait for LCD to process the data

ret ;Return from busy routine

; Usage of the above routine

; A will carry the character to display on LCD

; e.g. we want to print A on LCD

;

; mov a,#'A' ;Ascii value of 'A' will be loaded in accumulator

; acall LCD_senddata ;Send data

The equivalent C code Keil C compiler. Similar code can be written for SDCC.

CODE:

void LCD_senddata(unsigned char var)

{

LCD_data = var; //Function set: 2 Line, 8-bit, 5x7 dots

LCD_rs = 1; //Selected data register

LCD_rw = 0; //We are writing

LCD_en = 1; //Enable H->L

LCD_en = 0;

LCD_busy(); //Wait for LCD to process the command

}

// Using the above function is really simple

// we will pass the character to display as argument to function

// e.g.

//

// LCD_senddata('A');

SPEEDO METER RVCE

Depart of CSE 7

Inductive Proximity Sensor

Inductive Proximity Sensors

Inductive proximity sensors operate under the electrical principle of inductance.

Inductance is the phenomenon where a fluctuating current, which by definition has a

magnetic component, induces an electromotive force (emf) in a target object. To amplify a

device’s inductance effect, a sensor manufacturer twists wire into a tight coil and runs a

current through it. An inductive proximity sensor has four components; The coil, oscillator,

detection circuit and output circuit.

The oscillator generates a fluctuating magnetic field the shape of a doughnut around

the winding of the coil that locates in the device’s sensing face. When a metal object moves

into the inductive proximity sensor’s field of detection, Eddy circuits build up in the metallic

object, magnetically push back, and finally reduce the Inductive sensor’s own oscillation

field. The sensor’s detection circuit monitors the oscillator’s strength and triggers an output

from the output circuitry when the oscillator becomes reduced to a sufficient level.

SPEEDO METER RVCE

Depart of CSE 8

Interfacing of 8051 micro controller with Stepper motor

A Unipolar Stepper Motor is rotated by energizing the stator coils in a sequence. In unipolar

stepper, the direction of current in stator coils is not required to be controlled by the driving

circuit. Just applying the voltage signals across the motor coils or motor leads in a sequence

is sufficient to drive the motor.

A two phase unipolar stepper motor has a total of six wires/leads of which four are end wires

(connected to coils) and two are common wires. The color of common wires in the stepper

motor used here is Green. Each common wire is connected to two end leads thus forming two

phases. The end leads corresponding to each phase have to be identified.

In some cases, when the leads cannot be directly identified in the motor, the identification of

endpoints and common points can be done by measuring the resistance between the leads.

The leads of different phase will show open circuited condition with respect to each other.

This way the leads corresponding to different phase can be separated. The resistance between

any two end points of same phase will be twice the resistance between a common point and

an end point. This way the common and end points of both the phases can be identified.

SPEEDO METER RVCE

Depart of CSE 9

To work with the unipolar stepper motor, the common points are connected to either Ground

or Vcc and the end points of both the phases are usually connected through the port pins of

a microcontroller. In present case the common (Green) wires are connected to Vcc. The end

points receive the control signals as per the controller's output in a particular sequence to

drive the motor.

SPEEDO METER RVCE

Depart of CSE 10

Source code MAIN.SRC

#include <test_header.h>

ORG 0000H

LJMP MAIN

STR1: DB "COUNTER =$"

STR2: DB "DISTANCE=$"

MAIN:

LCALL INIT_RVCARD

LCALL LCD_INIT

MOV A,#00H

MOV DPTR,#STR1

LCALL LCD_PUTS_LINE1

MOV DPTR,#STR2

LCALL LCD_PUTS_LINE2

SENSOR_RELAY11:

; this is to demonostrate the use of SENSOR and RELAY

; P1.7 -- connected to Relay input

; P3.7 -- connected to Opto Isolator input i.e sensor input

; this program reads from the sensor and controls ac device connected to relay

; continuously and it is of indefinite loop

AAGAIN:JB P3.7,AAGAIN

/*MOV A,#25H

MOV B,#65H

MUL AB

MOV P0,B

LCALL DELAY

MOV P0,A*/

REL_ON1:

MOV P0,#0FFH

ADD A,#01

MOV R3,A

PUSH 0E0H

LCALL BINARY_TO_HEX

MOV A,#8DH

LCALL LCD_CWRITE

MOV A,R2

LCALL LCD_DWRITE

MOV A,R1

LCALL LCD_DWRITE

MOV A,R0

LCALL LCD_DWRITE

SPEEDO METER RVCE

Depart of CSE 11

MOV A,#02 //2*3.142*r(radius)*f(rotations per second)

MOV B,#01 //B contains radius 1 cm

MUL AB

MOV R4,A

MOV A,#03// ASSUMING PI VALUE AS 3

MOV B,R3 //NO OF ROTATIONS PER SECOND

MUL AB

MOV B,R4

MUL AB

LCALL BINARY_TO_HEX

MOV A,#8DH

ADD A,#40H

LCALL LCD_CWRITE

MOV A,R2

LCALL LCD_DWRITE

MOV A,R1

LCALL LCD_DWRITE

MOV A,R0

LCALL LCD_DWRITE

POP 0E0H

//LCALL DISP_DIST

AGAIN1: JNB P3.7,AGAIN1

SJMP SENSOR_RELAY11

SJMP $

END

SPEEDO METER RVCE

Depart of CSE 12

STEPPER.SRC

#include <test_header.h>

ORG 0000H

LJMP AA

STR1: DB "STEPPER MOTOR$"

AA: LCALL INIT_RVCARD

LCALL LCD_INIT

MOV DPTR,#STR1

LCALL LCD_PUTS_LINE1

STEP: MOV A,#88H

MOV R0,#100 ;100 steps in the clockwise direction

CONT:

MOV P0,A

LCALL DELAYMS

LCALL DELAYMS

RR A ;rotate the pattern in clockwise direction

//LCALL SENSOR_RELAY11

DJNZ R0,CONT

SJMP STEP

//LCALL SENSOR_RELAY11*/

/

SJMP $

END