Micro-Controller 8051: data acquisition and control system

1. It measures frequency directly.
2. By changing sampling or counting time , we can count pulses.
3. Auto resets after completing one counting time.
4. Displays the result for 2 Secs to note the number of pulses in that time.
5. Auto zeros, and start re-counting.
6. It allows manual operation like; start counting, Stop counting, reset to zero.
7. It allows user to change the time preset values of 0.1 Sec, 0.5 Sec, 1.0 Sec, 5.0 Sec, 10.0 Sec, 30.0 Sec, 60.0 Sec, and 120.0 Sec.
8. Easy to change to use different operations of counter.

1. Micro-controller 8051 family, in this project i used at89c51 but any 8051 family microcontroller can be used.
2. Multiplexed Seven Segment display (common anode) with six digit display is used.
3. The Seven segments are directly controlled and interfaced with port 0 of micro-controller.
4. Selection of digits is made with port 2 of at89c51 micro-controller.
5. As port P0 do not have internal pull-up resistors, so at this port external pull-up resistor network or pack of 10K x 8 is used.
6. In the schematic of counter / timer circuit , you will see, TTL 47ls04 inverter is used, it works fine, but if you feel the brightness of display is slightly low, then you can replace this with any general purpose PNP transistor.
7. To start and stop counting, a digital gate is used , this is formed with TTL 74ls08, the AND GATE, which have two inputs and one output. One of the input is connected to microcontroller port pin P3.2 and other is input of signals. when counting is started P3.2 goes to logic 1 (digital logic 1 means +5V). So the pulses now reached to port pin P3.3 of micro-controller. Which external Interrupt 1, the microcontroller 8051 external interrupt is used to count the incoming pulses.
8. When stop counting function is active, P3.2 goes to logic low, and now no-longer pulses can reach to controller.
9. Crystal used in this project is 11.0592.
10. The counter/ timer can be attached to computer (PC) with RS-232 interface.
11. The counter/ timer send result after each cycle (counting time ) to PC via serial port at Baud rate of 9600.
12. Hyper terminal can be used to view to save the incoming results on PC.

Main sub routines of the program written in keil C51 are as follows.

unsigned char digit,buffer[6],sec100,flag1,delay,nt;
unsigned char valu[6],sendtopc[18],msec,rmsec,tsec,rtsec,hhh;
char key;
unsigned char convert[10] = {0x28,0xee,0x49,0x4a,0x8e,0x1a,0x18,0x6e,0x08,0x0a};//afgb.dec
bit setting,held,sendnow;
sbit counts = P3^2;
void pause(int);
void scanLED();
void converter();
void freq();
void timer1 (void);
void extrint (void);
void seril(void);
void slect(void);
void timedisplay(void);
void startcounts(void);
void stopcounts(void);
void resetcounts(void);
void keyexe();
void keydelay();
void main(void)

{
sendtopc[0] = 0x54;//T
sendtopc[1] = 0x3d; //=
sendtopc[2] = 49; //1
sendtopc[3] = 50; //2
sendtopc[4] = 48; //0
sendtopc[5] = 0x2e; //.
sendtopc[6] = 48; //0
sendtopc[7] = 0x20; //SP
sendtopc[8] = 0x43; //C
sendtopc[9] = 0x3d; //=
sendtopc[10]= 0x54;
sendtopc[11]= 0x54;
sendtopc[12]= 0x54;
sendtopc[13]= 0x54;
sendtopc[14]= 0x54;
sendtopc[15]= 0x54;
sendtopc[16]= 0x0d;
sendtopc[17]= 0x0a;
setting = 1;
sec100 = 0;
rmsec = 120;
rtsec = 10;
msec = 0;
tsec = 0;
EA = 1;
TH1 = 0xfd; //(At 11.0592MHz) 0xf4 for 2400 and fd for 9600
TMOD = 0x21;
IT1 = 1;
EX1 = 1;
ET0 = 1;
TR1 = 1;
TR0 = 1;
hhh = 0;
held = 0;
sendnow = 0;
nt = 0;
counts = 1;
ES = 1;
SCON = 0x52;

while(1)
{
if(setting)
{
if(msec>=rmsec)
{
msec=0;
tsec ++;

if(tsec>=rtsec)
{
tsec=0;
counts=0;
held=1;
sendnow=1;
}
}

converter();

if(sendnow)seril();

if(held)
{
msec=0;tsec=0;sec100=0;
if(hhh>=254)
{
held=0;hhh=0;
valu[0]=0;valu[1]=0;
valu[2]=0;valu[3]=0;
valu[4]=0;valu[5]=0;
}
}
}
// else timedisplay();
scanLED();
keyexe();
keydelay();


}
}
void freq ()
{
if(held){hhh++; counts=0;}
else {sec100++;counts=1;}
if (sec100 >= 10) // 100 * 10 ms = 1 s //
{
msec++;
sec100 = 0;
}
}

void converter ()
{
unsigned char l;
for( l = 0; l <>

{ buffer[l]= convert [valu[l]]; } }

External Interuppt EX1, Timer T0 and T1 with serial Interruppt are used in this project.

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Labels: digital gate 74LS08, inverter 74LS 04, logical TTL pulses counter, multiplex seven segment six digit display, programmable frequency, timer