Fan Speed Control using 8051

Hi,

See the attachment

The freq of AC is 50Hz so T=1/50=20ms
T for per cycle will be =20ms/2=10ms.

From as per the calculation i need to generate the gate pulse at the interval of 10ms.
From the fig, Zero cross ref signal is of 10msecs which will be given to controller(INT0).
Now how to read this signal and generate the short pulse at the interval of 10ms.

are you sure your zero cross detector o/p is like that? can you post ZC detector circuit?
you can poll that pin state using a timer.. thats possible coz as per your attachment, ZC o/p state changes whenever your cycle changes..

as you are already connecting ZC o/p to interrupt pin. so whenever interrupt comes wait for some time and give a pulse. Only thing is the -ve AC cycle will not come into picture. this will not give you good results but will work.

Hi Ajay,

I have not developed zero cross detector ckt. I m searching for that ckt whose output of zero cross detector is as above fig. Now i m trying on proteus to the simulation as above.

Do u have working circuit for zero cross detector?

I have not developed zero cross detector ckt. I m searching for that ckt whose output of zero cross detector is as above fig. Now i m trying on proteus to the simulation as above.

Do u have working circuit for zero cross detector?

kirangowle

hello kiran!!

see the circuit below..... it will generate a pulse at every zero crossing....

see this video for more help... replace L1 with your fan in following circuit shown in video....

Hi Mirza,

Thanks dude your Zero crossing ckt is working fine.
In Hardware can i give directly 230V? r else i have to step down it.

Now i have to connect output of this ckt to 8051 interrupt pin.

no you have to use step down 220v ac.... never apply input directly its better to use step down transformer for it...... you can reduce input voltages by resistors like 120k in series with 220v but it will be dangerous not safe!! so i will suggest you to use transformer and then apply input to this circuit....

Hi,

I have written code for external interrupt. its a edge triggered interrupt.

#include<reg51.h>

sbit pulse=P1^1;
sbit led=P1^0;
void delay(unsigned int i);
unsigned int i;

void interrupt0(void) interrupt 0
{
	delay(0);
        pulse=1;	  // A short pulse making high to low 
	delay(0);
	pulse=0;
	led=1;
	delay(10);
}

void delay(unsigned int i)
{
        unsigned int k, l;
        for(k=0;k<i;k++)
                for(l=0;l<1000;l++);
}

void main(void)           //main function
{
IT0=1;       //int 0 is edge triggered
IE=0x83;   //enable all ints along with tr0(not used here actually) intr and int0

while(1)
{   
	led=0; 
} 
}

But the above code is not working
The input is square wave of 50hz freq.

well i am again doubtful.. about your zerocross output... i think you should give a check again... built it on hardware and see the output.

for safety you must use a transformer, but you can still make transformer-less zero cross detector. dont ask me how select the complete word "zerocross detector" and click learn more.

Hi,

I am wondering if I am using 120vac instead of 220vac. How to I choose the TRIAC, what model I should use?

thanks.