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cONSTRUcTION

108 • O ctO ber 2010 • electronics for you w w w . e f y m a g . c O m

HimansHu sHarma

Pulse Counterusing at89C4051

S u ni l K u ma r

Pulse counters are widely used in

our day-to-day life. Almost all

museums and theatres have a

visitor counter installed at entry/exit

to measure the visitor trafc. In indus-

tries, counting is done for production

control. Market tests too are performed

by counting the sold goods.

A pulse counter could be roughly

divided into three parts: a pulse

source, an electronic device that

counts, stores and prepares outputs,

and a display to show the accumulated

count.

This pulse counter is based on

Atmel AT89C4051 microcontroller.

TTL-logic-compatible pulses generated

by the source are fed to the counter

for counting. The AT89C4051 is a

low-voltage, high-performance, 8-bit

microcontroller with 4 kB of Flash

programmable and erasable read-only

memory, 128 bytes of RAM, 15 input/

output (I/O) lines, two 16-bit timers/

counters, a ve-vector, two-level inter-

rupt architecture, a full-duplex serial

port, a precision analogue comparator,

on-chip oscillator and clock circuitry.

System clock plays a signicant

role in operation of the microcontroller.

An 11.0592MHz quartz crystal pro-

vides basic clock to the microcontroller

(IC1) at its pins 4 and 5. Power-on reset

is provided by electrolytic capacitor C3

and resistor R1. Switch S1 is used for

manual reset.

Port pin P3.5 receives the input

pulse and the count is displayed on

the LCD as well as hyper terminal of

the PC. Pulse reception is indicated by

LED2, which is connected to port pin

Fig. 1: Circuit of microcontroller-based pulse counter

Parts List

Semiconductors:

IC1 - AT89C4051 microcontroller

IC2 - MAX232 RS-232 driverIC3 - 7805, 5V regulator

D1-D4 - 1N4007 rectier diode

LED1, LED2 - 5mm LEDLCD - 16-character × 2-line

Resistors (all ¼-watt, ±5% carbon):

R1 - 10-kilo-ohm

R2, R3 - 330-ohmR4 - 33-ohm

Capacitors:

C1 - 1000μF, 25V electrolyticC2 - 0.1μF ceramic diskC3 - 10μF, 16V electrolytic

C4, C5 - 33pF ceramic diskC6-C10 - 1μF, 16V electrolytic

Miscellaneous: X1 - 230V AC primary to 9V,

500mA secondarytransformer

S1 - Push-to-on switchX

TAL- 11.0592MHz crystal

- 9-pin D-type female COMport connector

- Heat-sink



cONSTRUcTION

electronics for you • O ctO ber 2010 • 10 9w w w . e f y m a g . c O m

LED1 acts as the power indicator andR2 limits the current through LED1.

Cc d

An actual-size, single-side PCB for the

microcontroller-based pulse counter

is shown in Fig. 2 and its component

layout in Fig. 3. Assemble the circuit

on a PCB as it minimises time and

assembly errors. Carefully assemble

the components and double-check

for any overlooked error. Connect the

assembled circuit to the COM port

of the computer. The accumulated

pulse count transferred is sent to the

PC through the COM port using the

HyperTerminal program. To open the

HyperTerminal program, go to Start →

Programs → Accessories → Communi-

cations → HyperTerminal. You will see

a window as shown in Fig. 4.

Type the desired name and click

‘ok.’ Select a COM port (refer Fig. 5)

while ignoring the other options andclick ‘ok.’

P3.7 of the microcontroller. Port pins

P1.0 through P1.7 of the microcontroller

are connected to data pins D0 through

D7 of the LCD, respectively. Port pins

P3.4, P3.3 and P3.2 are connected to

register-select RS, read-write R/W and

enable E of the LCD, respectively.

The data is sent to the LCD in

ASCII format for display. Only the

commands are sent in hex form to the

LCD. Register-select RS signal is used

to distinguish between data (RS=1)

and command (RS=0). Using preset

VR1, you can control the contrast of

the LCD. Resistor R4 limits the current

through backlight of the LCD.

Port pin P3.1 of the microcon-

troller is used to interface with the

PC’s hyper terminal through RS-232

interface MAX232 IC (IC2). The micro-

controller provides a transmit channelfor serial data transfer. Transmit data

pin (TXD) is speci-

ed at port pin P3.1.

The microcontroller

is connected to TIN

(pin 11) of MAX232.

TOUT

(pin 14) of IC2

is connected to pin 2of the COM port con-

nector. The signals

provided on these

pins are TTL-level

and must be boosted

and inverted through

a MAX232 converter

to comply with RS-

232 standard.

The MAX232 has

two internal charge

pumps that convert

+5V into ±10V (un-

loaded) for RS-232

driver operation. The

first converter uses

capacitor C8 to double

the +5V input to +10V

on capacitor C10 at

pin 2. The second con-

verter uses capacitor

C7 to invert +10V to

-10V on capacitor C6at pin 6.

All the serial com-

munication is controlled through

special-function register SCON. This

register contains mode-selection bits,

ninth data bit for transmit and receive

(TB8 and RB8), and serial-port interrupt

bits (TI and RI). Serial communication

requires standard baud rate. Timer-1

is congured in auto-reload mode to

generate baud rate. The baud rate is

determined as:

Baud rate =(32×12×(256 - TH1))

(2SMOD × Oscillator frequency)

The 230V, 50Hz AC mains is

stepped down by transformer X1 to

deliver a secondary output of 9V, 500

mA. The transformer output is recti-

ed by a full-wave rectier compris-

ing diodes D1 through D4, ltered by

capacitor C1 and regulated by IC 7805

(IC3). Capacitor C2 bypasses the rip-ples present in the regulated supply.

Fig. 4: Hyperterminal window for name and icon

Fig. 2: An actual-size, single-side PCB for microcontroller-based pulse counter

Fig. 3: Component layout for the PCB

Fig. 5: Hyperterminal window for COM port selection



cONSTRUcTION

110 • O ctO ber 2010 • electronics for you w w w . e f y m a g . c O m

to give the cor-

rect speed (9600

bits per second).

SCON gives the

necessary UART

signal and your

data is sent seri-ally. When port

pin P3.5 (T1)

goes low, the

internal coun-

ter increases by

one. This count

is displayed on the LCD as well as

hyper terminal of the PC.

EFY note. The source code of

this project has been included in this

month’s EFY-CD and is also available

on www.efymag.com website.

and serial interrupts. Then congure

the timer by mode and reload value

counter.c

Fig. 6: Hyperterminal window for selection of baud rate, data bits, parity, stop bits and fow control

Fig. 7: Count on hyperterminal screen

Now select the baud rate as ‘9600,’

data bits as ‘8,’ parity as ‘none,’ stop

bits as ‘1,’ ow control as ‘Xon/Xoff’

and click ‘ok’ (refer Fig. 6).

The microcontroller counts the

received pulses and sends the pulse

count to the hyper terminal and LCD.You will see a message on the screen

as shown in Fig. 8. Simultaneously, the

pulse count appears on the LCD.

sfw

The software for this project is given

at the end of this article. It is written in

‘C’ language and compiled using Keil

μVision4 compiler. Burn the generated

hex code into the microcontroller using

a suitable programmer.

In the software, rst enable timer

#include<reg51.h>#dene LCD P1unsigned int Count,d1,d2,d3,d4,x1,x2,x3,x4;sbit Pulse = P3^5;sbit LED = P3^7;sbit rs = P3^4;sbit rw = P3^3;sbit en = P3^2;void LCDInit ();void lcdcmd (unsigned char);void lcdwrt (unsigned char);void Delay (unsigned int);void Convert (unsigned int);void SerialTx (unsigned char);void main(void){

unsigned char z,Display;unsigned char code str1[]=”

PULSE COUNTER “;unsigned char code str2[]=”

Design By “;unsigned char code str3[]=”

HIMANSHU “;unsigned char code str4[]=”

SHARMA “;unsigned char code str5[]=”PULSE:

0000 “;P0=0xFF;P1=0xFF;P2=0xFF;P3=0xFF;IE=0x00;Count=0x00;

///////SERIALIZATION DATA///////TMOD = 0x20;TH1 = 0xFD;SCON = 0x50;TR1 = 1;

LED = 0x00;LCDInit();for(z=0;z<16;z++){

Display=str1[z];lcdwrt(Display);Delay(1);SerialTx(Display);Delay(1);

}SerialTx(‘\r’);SerialTx(‘\n’);lcdcmd(0xC0);for(z=0;z<16;z++){


}Delay(200);SerialTx(‘\r’);

SerialTx(‘\n’);lcdcmd(0x01);

Delay(1);for(z=0;z<16;z++)

{Display=str3[z];lcdwrt(Display);Delay(1);SerialTx(Display);Delay(1);

}SerialTx(‘\r’);SerialTx(‘\n’);lcdcmd(0xC0);for(z=0;z<16;z++){

Display=str4[z];lcdwrt(Display);

Delay(1);SerialTx(Display);Delay(1);

}Delay(200);SerialTx(‘\r’);SerialTx(‘\n’);lcdcmd(0x01);Delay(1);lcdcmd(0xC0);for(z=0;z<16;z++){


}Delay(70);SerialTx(‘\r’);SerialTx(‘\n’);while(1)

{ LED=1;Delay(30);if(Pulse==0){

Count=Count+1;Convert(Count);if(Count==9999)

Count=0x00;}

}}void Convert(unsigned int value){

x1 = value / 10;d1 = value % 10;x2 = x1 / 10;d2 = x1 % 10;x3 = x2 / 10;d3 = x2 % 10;d4 = x3 % 10;d1=d1|0x30;

d2=d2|0x30;d3=d3|0x30;

d4=d4|0x30;lcdcmd(0xC7);lcdwrt(d4);lcdwrt(d3);lcdwrt(d2);lcdwrt(d1);Delay(1);SerialTx(d4);SerialTx(d3);SerialTx(d2);SerialTx(d1);Delay(1);SerialTx(‘\r’);SerialTx(‘\n’);LED=0;Delay(30);

}void LCDInit(){

lcdcmd(0x38);Delay(10);lcdcmd(0x0E);Delay(10);lcdcmd(0x01);Delay(10);lcdcmd(0x0C);Delay(10);lcdcmd(0x80);Delay(10);return;

}void lcdcmd(unsigned char value){

LCD=value;rs=0;rw=0;en=1;Delay(1);

en=0;return;}void lcdwrt(unsigned char value){

LCD=value;rs=1;rw=0;en=1;Delay(1);en=0;return;

}void SerialTx(unsigned char value){

SBUF = value;while(TI==0);TI = 0;

}void Delay(unsigned int x){

unsigned int i,j;for (i=0;i<=x;i++)

for (j=0;j<=500;j++);}

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