Hey guys,
I bought this kit and it works pretty nicely.

I'm now trying to make it so that at certain temperatures different fan speeds would go off.

    if(tempA>300&&tempA<400) { //300 equals 30°C
 //set speed
}else if(tempA>=400){
//set speed 2
                }

The kit I bought is below

http://tinyurl.com/yf7dngw

and here is the C source

//==========================================================================
//    Author                : Cytron Technologies        
//    Project                : Temperature Control System using LM35
//    Project description    : This project will use PIC16F876A to control NPN power transistor (BD135) 
//                          further drive DC brushless fans, LEDs and buzzer when the certain 
//                          temperature was detected. 
//==================inckude=================================
#include<pic.h>

//===============configuration==============================
__CONFIG (0x3F32);

//==========define IO port=========
#define        lcd            PORTC
#define        RS            RA2
#define        E            RA5
#define        CHANNEL0    0b10000001    // AN0
#define        CHANNEL1    0b10001001    // AN1
#define        buzzer        RB5
#define        fanA        RB4
#define        fanB        RB3
#define        ledA        RB2
#define        ledB        RB1

//==============FUNCTION PTOTOTYPE==============
void e_pulse(void);
void delay(unsigned short i);
void send_char(unsigned char data);
void send_config(unsigned char data);
void lcd_goto(unsigned char data);
void lcd_clr(void);
void dis_num(unsigned long data);
void increment(unsigned long data);
void read_adc(void);
unsigned short read_temp(void);

unsigned short result;
unsigned short temp,tempA,tempB;

void main(void)
{
    ADRESH=0;                    //clear A/D result
    ADRESL=0;                    //clear A/D result

    //setting ADCON1 Register
    ADCON1=0b11000101;            // A/D result right justified,                 
                                // configure RA2 and RA5 as digital I/O

    TRISA=0b11011011;            //configure PORTA I/O direction
    TRISB=0b00000000;            //configure PORTB as output
    TRISC=0b00000000;            //configure PORTC as output

    PORTA=0;
    PORTB=0;
    
    while(1)                    
    {
        send_config(0b00000001);        //clear display at lcd
        send_config(0b00000010);        //Lcd Return to home 
        send_config(0b00000110);        //entry mode-cursor increase 1
        send_config(0b00001100);        //diplay on, cursor off and cursor blink off
        send_config(0b00111000);        //function set
        
        lcd_goto(0);                    //cursor start from beginning
        
        //display character on LCD
        send_char(' ');
        send_char('T');
        send_char('E');
        send_char('M');
        send_char('P');
        send_char('.');
        send_char('A');
        send_char('=');    

        lcd_goto(20);                    //cursor go to 2nd line of the LCD

        //display character on LCD
        send_char(' ');
        send_char('T');
        send_char('E');
        send_char('M');
        send_char('P');
        send_char('.');
        send_char('B');
        send_char('=');    

        while(1)                        //infinity loop
        {
        //sensor A
        ADCON0=CHANNEL0;                //CHANNEL1=0b10001001
        lcd_goto(8);
                
        read_adc();

        temp=read_temp();
        dis_num(temp/10);
        send_char('.');
        dis_num(temp%10);
        send_char(0b11011111);
        send_char('C');
        send_char(' ');
        send_char(' ');
        
        tempA=temp;
        
        //sensor B
        ADCON0=CHANNEL1;                //CHANNEL0=0b10000001            

        lcd_goto(28);
                
        read_adc();

        temp=read_temp();
        dis_num(temp/10);
        send_char('.');
        dis_num(temp%10);
        send_char(0b11011111);
        send_char('C');
        send_char(' ');
        send_char(' ');

        tempB=temp;
    
            if((tempA>400)&&(tempB<350))        //    *****************************************
                {                                //    *    LED A and Fan A activated only for     *
                    ledA=1;                        //    *    temperature A greater than 40'C        *
                    ledB=0;                        //    *    and temperature B less than 35'C    *
                    fanA=1;                        //    *****************************************
                    fanB=0;
                    buzzer=0;
                }    

            else if((tempB>350)&&(tempA<400))     //    *****************************************
                {                                //    *    LED B and Fan B activated only for     *
                    ledA=0;                        //    *    temperature A less than 40'C and    *
                    ledB=1;                        //    *    temperature B greater than 35'C        *
                    fanA=0;                        //    *****************************************
                    fanB=1;
                    buzzer=0;
                }    

            else if((tempB>350)&&(tempA>400))     //    *****************************************************
                {                                //    *    All LED A & LED B, Fan A & Fan B and Buzzer        *
                    ledB=1;                        //    *    activated for temperature A greater than 40'C    *
                    ledA=1;                        //    *    and temperature B greater than 35'C                *
                    fanA=1;                        //    *****************************************************
                    fanB=1;
                    buzzer=1;
                }    

            else if((tempB<350)&&(tempA<400))    //    *****************************************************
                {                                //    *    All LED A & LED B, Fan A & Fan B and Buzzer        *
                    ledB=0;                        //    *    disactivated for temperature A less than 40'C    *
                    ledA=0;                        //    *    and temperature B less than 35'C                *
                    fanA=0;                        //    *****************************************************
                    fanB=0;
                    buzzer=0;
                }    

        delay(2000);
    
        }
    
    }
        
}
        
                    

//==================subroutine LCD setting ==========================

void send_config(unsigned char data)
{
     RS=0;
    lcd=data;
    delay(500);
    e_pulse();
}

void e_pulse(void)
{
    E=1;
    delay(500);
    E=0;
    delay(500);
}

void send_char(unsigned char data)
{
     RS=1;
    lcd=data;
    delay(500);
    e_pulse();
}


void lcd_goto(unsigned char data)
{
     if(data<16)
    {
         send_config(0x80+data);
    }
    else
    {
         data=data-20;
        send_config(0xc0+data);
    }
}


void lcd_clr(void)
{
    RS=0;
     send_config(0x01);
    delay(600);    
}


void dis_num(unsigned long data)
{
    unsigned char hundred_thousand;
    unsigned char ten_thousand;
    unsigned char thousand;
    unsigned char hundred;
    unsigned char tenth;

    hundred_thousand = data/100000;                    
    data = data % 100000;
    ten_thousand = data/10000;
    data = data % 10000;
    thousand = data / 1000;
    data = data % 1000;
    hundred = data / 100;
    data = data % 100;
    tenth = data / 10;
    data = data % 10;

    if(hundred_thousand>0)
    {
        send_char(hundred_thousand + 0x30);    //0x30 added to become ASCII code
        send_char(ten_thousand + 0x30);
        send_char(thousand + 0x30);
        send_char(hundred + 0x30);
        send_char(tenth + 0x30);
        send_char(data + 0x30);
    }

    else if(ten_thousand>0) 
    {
        send_char(ten_thousand + 0x30);    //0x30 added to become ASCII code
        send_char(thousand + 0x30);
        send_char(hundred + 0x30);
        send_char(tenth + 0x30);
        send_char(data + 0x30);
    }
    else if(thousand>0)
    {
         send_char(thousand + 0x30);    //0x30 added to become ASCII code
        send_char(hundred + 0x30);
        send_char(tenth + 0x30);
        send_char(data + 0x30);
    }
    else if(hundred>0)
    {
         send_char(hundred + 0x30);    //0x30 added to become ASCII code
        send_char(tenth + 0x30);
        send_char(data + 0x30);
    }
    else if(tenth>0)
     {
        send_char(tenth + 0x30);    //0x30 added to become ASCII code
        send_char(data + 0x30);
    }
    else send_char(data + 0x30);    //0x30 added to become ASCII code
}

void increment(unsigned long data)
{    
    unsigned short j;
    for(j=10;j>0;j--)
    {    lcd_goto(32);
        data=data+1;
        dis_num(data);
        delay(10000);
    }

}

//==================subroutine ADC=========================

void read_adc(void)
{
    unsigned short i;
    unsigned long result_temp=0;
    for(i=2000;i>0;i-=1)            //looping 2000 times for getting average value 
    {
        ADGO = 1;                    //ADGO is the bit 2 of the ADCON0 register
        while(ADGO==1);                //ADC start, ADGO=0 after finish ADC progress
        result=ADRESH;
        result=result<<8;            //shift to left for 8 bit
        result=result|ADRESL;        //10 bit result from ADC

        result_temp+=result;        
    }
    result = result_temp/2000;        //getting average value

}

unsigned short read_temp(void)
{
    unsigned short temp;
    temp=result;
    return temp;

}


void delay(unsigned short i)
{    
    for(;i>0;i--);
}

How do I change it from just turning on the fan to controling the fan speed?

 

Hi,
For changing fan speed, use PWM.
For mikroBASIC in say 18F452, something like this can be done:

program FanSpeedTemp
dim ADRead as word
const Temp30 61
main:
   TRISC = 0
   TRISA = 0xFF
   PWM_Init(5000) 'Set PWM frequency at 5kHz
   PWM_Set_Duty(128) 'Set PWM duty cycle at 50%
   PWM_Start() 'Start PWM
   while true
      ADRead = ADC_Read(0)
      if ADRead > Temp30 then 'If ADC reads a temp value greater than 30'C
         PWM_Set_Duty(192) '75% duty cycle
      else
         PWM_Set_Duty(64) '25% duty cycle
      end if
   wend
end.

Set Duty cycle as:
PWM_Set_Duty(val)
val = Required duty cycle * 256
So, for 90%, val = 0.9 * 256 = 230

Hope this helps.
Tahmid.