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My bedside fan’s mechanical timer is broken, so I designed a simple timer controller using the 51 microcontroller. The program has been initially debugged on the experimental board, and I’m waiting for the components to arrive to make the board, although it seems a bit wasteful of the microcontroller’s resources.
1. Design Idea:
Initially, power is supplied to the microcontroller manually via a button. Once the power indicator LED4 lights up, the microcontroller runs, and Relay 2 works to supply power to the microcontroller. The working time of Relay 2 can be set via buttons to achieve automatic power-off, and the working time of Relay 1 can be set to achieve intermittent operation of the fan for energy saving.
1. Display Section: Using buttons, the display can switch between the fan’s running time, pause time, and the remaining time until the system shuts down. The digital display shows two digits for “minutes”, while the remaining time until the system shuts down is displayed in “hours”. The LEDs are red, yellow, and blue, respectively indicating the states of the fan running, paused, and the remaining time until the system shuts down.
2. Button Section:
l K1 is the time adjustment shift key. When pressed, the display digits flash, and the corresponding light flashes. It switches between the fan running time, pause time, and system.
l K2 is the increment and state switch display key. When K1 is pressed, it adds 1 to the time. Otherwise, it switches the display between the fan running time, pause time, and system.
l K3 is the decrement and standby key. When K1 is pressed, it adds 1 to the time; otherwise, it has no effect.
3. Relay Section:
l Relay 1 controls the power line of the fan, enabling its operation and pause.
l Relay 2 controls the power of the microcontroller system, enabling the system to shut down on a timer.
2. Schematic Diagram
3. Program Listing
/*********************************************
System Name: Simple Timer Controller for Fan
Creator: w418781840 Date: 2008.7.6
System Functions:
**********************************************/
/*********************************************
Function Name: Declaration Area
Function Description:
**********************************************/
#include
#define uchar unsigned char
#define uint unsigned int
#define SEG P0 // Segment selection for digital tube.
#define DIG P2 // Digit selection for digital tube
uchar dis[2]; // Digital drive group
uchar code TAB[]={ 0xC0,0xF9,0xA4,0xB0,0x99,//0-4 common anode.
0x92,0x82,0xF8,0x80,0x90,0xff};//5-9, off symbol
uchar start,stop,close,sum,time; // Basic variables
uchar fliflag,cflag,zflag,x,y;// Flag bits
uint count_T0,count_T1,c_count; // Counting variables
sbit K1=P3^7; // Function shift key
sbit K2=P3^2; // Increment key and switch shift key.
sbit K3=P3^3; // Decrement.
sbit RLED=P2^2; // Red light, indicates fan running status.
sbit YLED=P2^3; // Yellow light, indicates fan paused status
sbit BLED=P2^4; // Blue light, indicates system status
sbit CLED=P2^6; // Fan control bit
sbit ZLED=P2^7; // System operation control bit
/*********************************************
Function Name: Delay 1ms Function
Function Description: Display call.
**********************************************/
void delay1ms(uchar x)
{
uchar i,j;
for(i=0;i for(j=0;j<120;j++);
}
/*********************************************
Function Name: Display Function
Function Description: Display minutes, two digits.
**********************************************/
void display(void)
{
uchar i,scan=1;
for(i=0;i<2;i++)
{ SEG=0xff;
DIG=~scan;
SEG=TAB[dis[i]];
delay1ms(5);
scan<<=1;
}
}
/*********************************************
Function Name: Delay 5ms Function
Function Description: Key debounce call.
**********************************************/
void delay5ms(uchar x)
{
uchar j;
for(j=0;j display();
}
/*********************************************
Function Name: Initialization Function
Function Description: Initialize each variable.
**********************************************/
void init()
{ fliflag=0;// Flashing flag.
cflag=1; // Fan state flag.
zflag=0; // Running flag.
x=30; // Temporary storage
y=10; // Temporary storage
CLED=1;// System operation.
sum=0; // Shift
start=30; // Fan running time
stop=10; // Pause time.
close=5; // Remaining time until system shuts down
count_T0=0; // Related to T0,T1
count_T1=0;
c_count=0;
TMOD=0x11;
TH0=(65536-50000)/256;
TL0=(65536-50000)%256;
TH1=(65536-50000)/256;
TL1=(65536-50000)%256;
EA=1;
ET0=1;
ET1=1;
TR0=1;
}
/*********************************************
Function Name: Split Function
Function Description: Split display into tens and units
**********************************************/
void disnner(void)
{ if(cflag==1)//1
{ RLED=0;YLED=1;BLED=1;// Red light flashes.
time=start; // Display running time.
}
if(cflag==2)
{ RLED=1;YLED=0;BLED=1;
time=stop;
}
if(cflag==3)
{ RLED=1;YLED=1;BLED=0;
time=close;
}
dis[0]=time/10;
dis[1]=time%10;
}
/*********************************************
Function Name: T0 Interrupt Function
Function Description: Generate 1 minute.
**********************************************/
void timer0(void)interrupt 1
{ TH0=(65536-50000)/256;
TL0=(65536-50000)%256;
if(++count_T0==1200)// one minute.
{ count_T0=0;
if(zflag==0) // is 0
{ ZLED=1; // then rotate.
if(start!=99)// If running time is 99, display 99, do not switch flag. Keep rotating.
{
start–; // If not, countdown.
if(start==0)
{ zflag=1;// Countdown time is up. Switch flag.
cflag=2;
start=x;// Reassign
}
}
}
else
{ ZLED=0; // Otherwise pause.
stop–; // Countdown.
if(stop==0)
{ cflag=1; // Time is up.
zflag=0;
stop=y;
}
}
if(close!=99)// If system time is 99, display 99, system always works..
{ if(++c_count==60) // Count to 60 for one minute, that is, after one hour.
{ c_count=0;
close–; // Do a one-hour countdown.
if(close==0) // Time is up, system powers off.
CLED=0; // Low level is effective.
}
}
}
disnner();// Separate. Send display/
}
/*********************************************
Function Name: T1 Interrupt Service Function
Function Description: Adjust time for flashing.
**********************************************/
void timer1(void)interrupt 3
{
TH1=(65536-50000)/256;
TL1=(65536-50000)%256;
if(++count_T1==6)// Flashing period 30MS
{
count_T1=0;
fliflag=~fliflag; // Toggle
if(fliflag==0) // Flag is effective.
{
if(sum==1)cflag=1;// Use state flashing.
if(sum==2)cflag=2;
if(sum==3)cflag=3;
disnner(); // For flashing.
dis[0]=10; // Turn off symbol.
dis[1]=10;
}
else // Otherwise, normal display.
{
RLED=1;YLED=1;BLED=1;
dis[0]=time/10;
dis[1]=time%10;
}
}
}
/*********************************************
Function Name: Key Scanning Function
Function Description: Adjust time
**********************************************/
void scanner(void)
{ if(K1==0) // If 0, it indicates a key is pressed.
{
delay5ms(100);// Delay 500MS.
if(K1==0) // Still pressed. Just released.
{
while(K1==0)display();// Wait for release.
delay5ms(2); // Debounce.
cflag=1; // Exit display state 1.
count_T0=0;
TR0=1; // Start T0
TR1=0; // Turn off flashing
sum=0; // Reset.
x=start; // Temporary storage.
y=stop; // Temporary storage.
}
else
{ // Otherwise, a shift key is pressed.
TR0=0; // Stop time movement.
TR1=1; // Turn on flashing.
sum++; // Shift.
if(sum==4)
sum=1;
}
}
if(K2==0)
{
delay5ms(2);
if(K2==0)
{
while(K2==0)display();
delay5ms(2);
if(sum) // If shift
{ if(sum==1)
{
start++;
if(start==61)
start=99;
if(start==100)
start=30;
}
if(sum==2)
{
stop++;
if(stop==61)
stop=5;
}
if(sum==3)
{
close++;
if(close==9)
close=99;
if(close==100)
close=1;
}
}
else // No shift.
{
cflag++; // Then proceed to display state shift.
if(cflag==4)
cflag=1;
}
}
}
if(K3==0)
{
delay5ms(2);
if(K3==0)
{
while(K3==0)display();
delay5ms(2);
if(sum==1)
{ start–;
if(start==29)
start=99;
if(start==98)
start=60;
}
if(sum==2)
{ stop–;
if(stop==4)
stop=60;
}
if(sum==3)
{ close–;
if(close==0)
close=99;
if(close==98)
close=8;
}
}
}
}
/*********************************************
Function Name: Main Function
Function Description:
**********************************************/
main()
{
init();
while(1)
{
display();// Display
scanner(); // Detect keys..
}
}
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