Automatic Changeover Controller (ATS) Control Card with PIC16F88 (Version 1)

🔌 Automatic Changeover Controller (Prototype V1)

1. Terminal Blocks

• 12V DC Input Block (2 screws):
  
  
  Supplies regulated 12VDC to the circuit, typically from the GENSET battery, to power the controller.

• AC Sensing Block (3 screws):
  
  
  Used for sensing 220V AC signals from both mains and GENSET.
  • Middle screw → Neutral line (common for both supplies).
  • Side screws → Phase line of mains and phase line of GENSET.
  • Each screw is clearly labeled on the PCB.
• Relay Control Blocks (2 screws each):
  Connected to:

  1. Switch Relay

  2. Crank Relay

  3. Changeover Relay Driven by microcontroller GPIOs.

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2. Transformers

• Step-down Transformers (220V → 12V):
  
  
  Used to reduce mains and GENSET phase signals to a safe level for the microcontroller.

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3. Rectifiers

• Two rectifiers (1A rating):
  
  
  Each phase signal passes through a separate rectifier, converting 12VAC → 12VDC for conditioning.

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4. Voltage Regulators

• 7805 Regulators:
  Convert rectified 12VDC signals to 5VDC.

• Signal Conditioning:
  • Each sensing line includes a 10kΩ pull-down resistor (ensures clean logic levels).
  • 470µF capacitors are used on each line for stability and noise suppression.

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5. Microcontroller (PIC16F88)

The PIC16F88 monitors input signals and controls relays accordingly.

Controller Logic:

1. Case 1 – Mains Present, GENSET Off
   
   
   → Keep all relays OFF.

2. Case 2 – Mains Off, GENSET Off
   
   
   • Wait 30s, energize Switch Relay.
   • After 2s, energize Crank Relay for 4s.
   • Check GENSET signal for 10s.
     
     
     • If not detected, repeat crank cycle (up to 6 attempts).
   • Once GENSET detected →
     
     
     • Keep Switch Relay ON, Crank Relay OFF.
     • Energize Changeover Relay → Load shifts to GENSET.
3. Case 3 – Mains Restored
   
   
   • Detect mains presence.
   • Wait 10s, then turn OFF Changeover Relay (load back to mains).
   • After 3s, turn OFF Switch Relay → GENSET turns off.
4. Case 4 – Both Supplies Off
   
   
   • Retry GENSET startup process (same as Case 2).

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6. Relays

• Relay 1 – Switch Relay: Turns ON GENSET.
• Relay 2 – Cranking Relay: Engages GENSET starter motor.
• Relay 3 – Transfer (Changeover) Relay: Switches load between mains and GENSET.

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7. Relay Driver IC

• ULN2003:
  Acts as an interface between 5V microcontroller outputs and 12V relay coils.
  Provides current amplification and safe isolation.

Visit Our other PIC Microcontroller Projects

Interface 7 Segment 4x1 with PIC controller using PIC controller

The falling edge detection code Using PIC16F877A and MikroC Compiler

Edge activation is very important for counting or any enabling application. so here we are going to discuss falling edges to activate or detect the falling edges. This is a very important example we are sharing with all.

counter count on falling edge (press the button it will not count but when the button is released then counter increment or decrement depending on the application.

Related topic:

• Interface 7 Segment 4x1 with PIC controller using PIC controller 

I have discussed the falling edge issue in this topic too, but the given topic is on Multiplexing of 7 segments.

Falling edge detection is very tough for electronic players so we are going to solve this problem in coding by using the compiler MikroC pro for PIC16F877A and Simulate it on Proteus 8.15 for testing.

What is Falling Edge?

The falling edge of the clock means that when the clock pulse goes to low from high level that makes high to low a shorter time edge. You can be seen here in the diagram as illustrated.

On the way, we will also discuss the multi-press problem solution for the button here. 

What multi-press of buttons?

For example, we have created a counter application circuit using a PIC microcontroller and wrote the code to Count up when the push button is pressed. here is the problem when we write a simple code. we press one time but the microcontroller reads it many times and the counter scrolls up many numbers with a single click.

Code chunk example:

while(1){

if (button ===1){

counter++;

Lcd_Out(1,1,counter);

}

}

Multipress Problem:

In starting coding experiments I used delay before counter++  to solve this problem but it was not as practical as I wanted or you wanted to. then I have to use a method that works perfectly on the edges of the clock and also resolve the multipress problem.

Here we are sharing with you all. 

See the results here using Proteus 8.15 Simulations:

Circuit Diagrams

You can download the circuit in PDF format:

 

MikroC Coding Chunk:

while(1)

     {// UP counting using Falling Edge

      led=0;

      if(up==1){up_pr++;}

       // Here is a technique when we press the button then

       // increment in an int variable

      if(up==0 && up_pr>=1)

      // Now here apply the condition when (button depress

      // and up_pr>=1) then apply the action function as under

        {count++;led=1;Delay_ms(100);up_pr=0;}

      // DOWN counting using Falling Edge

      if(down==1){down_pr++;}

      if(down==0 && down_pr>=1){if(count>0){count--;}

                               down_pr=0;}

      if (rst==1){count=0;} // Reset the counter

So by this, I have Solve the Problem ..... Enjoy

Scrolling text on Dot-Matrix Using PIC controller & MikroC Pro

 Dot Matrix is the combination of LEDs in Matrix form in different sizes. Dot Matrix LED display use to display any type of text on it, but on 7 segment we can display digits only. We can see the Dot Matrix Display in marketing for advertising and in other different application to display some text.

Related Topic: 

• Dot matrix display projectwith static display
• Interface 7 Segment 4x1 with PIC controller using PIC controller
• PIC Microcontroller Manuals 

So here we are sharing the scrolling text on dot matrix. MikroC Pro for PIC is use for coding and compilation and Proteus 8.15 is use for simulation for circuit testing.

Dot-Matrix concept:

Working of dot matrix:

Here we are using common cathode dot matrix, it means the Anodes of the LEDs are common with columns and cathode with rows as you can see in above 1^st diagram.

If we want to ON top left dot, then we will do column 1 high and row 1 low. Here if we will scan columns and row 1 low all others row at high then top row of the matrix will glow one by one from left to right. Wise versa if we scan rows and select to high one column then selected column dots glow one by one.

Interesting this is that if we increase the scanning speed and cross the human eye flickering sensitivity then we see a line of row or column.

Circuit diagram:

Circuit designed in Proteus8.15

MikroC Pro for PIC Coding:

/// Dot Matrix 5x7 using PIC ///
/// by Elektronics Garage    ///
/// Date: 4 Nov 2023         ///

//Dot_Matrix size
unsigned int columns = 10;
unsigned int rows = 7;
unsigned int loop=0;
unsigned int col=0;
unsigned int row=0;
int int i,j;
unsigned int col_num[] = {0x01,0x02,0x04,0x08,0x10,0x01, 0x02, 0x04, 0x08, 0x10};
unsigned int row_A[] = {0x01, 0x76, 0x76, 0x76,0x01,0xFF,0xFF,0xFF,0xFF,0xFF};
unsigned int row_B[] = {0x00, 0x36, 0x36, 0x36,0x49,0xFF,0xFF,0xFF,0xFF,0xFF};

void main() {
TRISB=0x00;
TRISD=0x00;
PORTB=0x00;
PORTD=0x00;

col=columns-1; 

while(1) {

for (j=0;j<300 delay_us="" else="" for="" i="" if="" j="" loop="" portb="col_num[col-i];" portd="row_A[row];" row="loop;">col-1){loop=0;}
}
}

Interface 7 Segment 4x1 with PIC controller using PIC controller

Interface 7 Segment 4x1 with PIC controller using PIC controller

7 Segment display use to display the values in form of digits. So it’s important to learn 7 segment and how to drive single 7 segment using different controllers and that code programs in different compilers. The basic Concept remain same. So here we are going to drive 4 digit 7 segment using PICcontroller and compile it working code in MikroC pro for PIC.

After coding compilation its important to test it on circuit so we use Proteus 8.15 for simulation.

For types of 7 segments see this topic:7 Segment Interfacewith PIC Microcontroller as Up Counter

4 digit 7 segment in Proteus:

PINOUT of 4 digit 7 segment:

Example to Display the 4 digits value:

1234 is value for example:

4 is at unit position

3 is at 10^th position

2 is at 100^th position and

1 is at 1000^th position

When we will display 4 then we select unit digit by using pin DG1 and send the data of 4 (in form of binary which drive the 7 segment)

See this table:

Digit	Dp	G	F	E	D	C	B	A	Hex
0	0	0	1	1	1	1	1	1	0x3F
1	0	0	0	0	0	1	1	0	0x06
2	0	1	0	1	1	0	1	1	0x5B
3	0	1	0	0	1	1	1	1	0x4F
4	0	1	1	0	0	1	1	0	0x66
5	0	1	1	0	1	1	0	1	0x6D
6	0	1	1	1	1	1	0	1	0x7D
7	0	0	0	0	0	1	1	1	0x07
8	0	1	1	1	1	1	1	1	0x7F
9	0	1	1	0	1	1	1	1	0x6F

 

And we are using decoder 74LS138 Mux IC to select the 7 segment digits and saving the pins of controller. We are using Just for 4 output control red blocked area of the table.

When we will display 3 then we select 10^th digit by using pin DG2 and send the data of 3.

When we will display 2 then we select 100^th digit by using pin DG3 and send the data of 2.

When we will display 1 then we select 1000^th digit by using pin DG4 and send the data of 1.

Circuit Diagram:

MikroC coding:

/// Multiplexed 7 Segments ///
/// Eleltronics Garage     ///
/// By: Fayyaz Hussain     ///
///   29 Oct, 2023         ///

int count=0;
void counter();

int up_pr=0,down_pr=0,digit1=0,digit2=0,digit3=0,digit4=0;

// Array of 7 Segment display decoder
unsigned int seg_num[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};

sbit up at RD4_bit;  // Up count Button
sbit down at RD5_bit;// Down count Button
sbit rst at RD6_bit; // Reset to 0 button

sbit A at RD0_bit; // Decoder 74LS138 IC INPUT A,B
sbit B at RD1_bit; //

void main() {
TRISB=0x00;
TRISD=0xF0;
PORTB=0x00;
PORTD=0x00;

while(1)
     {// UP counting using Falling Edge
      if(up==1){up_pr++;}
      if(up==0 && up_pr>=1){count++;up_pr=0;}
      
      // DOWN counting using Falling Edge
      if(down==1){down_pr++;}
      if(down==0 && down_pr>=1){if(count>0){count--;}
                               down_pr=0;}
            
      if (rst==1){count=0;} // Reset the counter

counter(); // function to define digits position
     // Unit position Digit
     B=0;A=0;
     PORTB=seg_num[digit1];
     Delay_ms(2);
     // 10th position digit
     B=0;A=1;
     PORTB=seg_num[digit2];
     Delay_ms(2);
     // 100th position Digit
     B=1;A=0;
     PORTB=seg_num[digit3];
     Delay_ms(2);
     // 1000th position Digit
     B=1;A=1;
     PORTB=seg_num[digit4];
     Delay_ms(2);
     }
}

void counter()
{
digit1 = count%10;
digit2 = (count%100)/10;
digit3 = (count%1000)/100;
digit4 = count/1000;
}