DC motor control using PIC

 When using PIC to control DC motor, the motion of motor such as forward, reverse,and speed of rotation can be programmed. If the motion of motor only required forward and reverse without considering the speed of rotation, motor can be control through relay module. the are two example of relay module which can be use by PIC to control DC motor. First figure is to control only On and OFF of motor which also compatible to other devices that are using switch. Second figure can be used to control forward and reverse motion of DC motor.

 

By using relay module, it is very easy to control the motion of motor. The programming part only require ON and OFF of output PORT.

Example of simple forward reverse motor control using 2 switches connected to RD0 and RD1:

main()

{

while (1)

{

TRISD = 0b00000011;

PORTB = 0b00000000;

TRISB = 0b00000000;

PORTB = 0b00000000;

if (PORTDbits.RD0 == 1 && PORTDbits.RD1 == 0)

 PORTB = 0b00000010;

if (PORTDbits.RD0 == 0 && PORTDbits.RD1 == 1)

 PORTB = 0b00000010;

else

PORTB = 0b00000000;

 }

}

 When DC motor require speed control, the speed of DC motor can be control by various techniques including Pulse Width Modulation (PWM), power transistor, driver IC etc. The diagram below is example of DC motor controlled by transistor and PWM.

 

Whenever there is input voltage supplied to Base pin of the transistor, the transistor will turned ON and let the current flow through. with different speed of PWM provided, the speed of motor can be adjusted. The faster the PWM signal, the faster the motor will rotate.

 

Analog - Digital convertion with PIC

PIC 18F4550 come with ADC in PORT A which reads analog input such as:

1. voltage

2. temperature

3. light intensity

4. resistance

5. moisture 

6. humidity etc

Analog signal is converted into digital form by referring to reference voltage which can be set to Vdd (same as source voltage) or any other external reference voltage source. ADC Module has high-voltage reference (Vref+) and low-voltage reference (Vref-). The reference voltage value can be chose to be Vdd, VSS, RA2 or RA3. ADC Module from Channel 0-7 (AN0-AN7) will read the voltage value detected from the chosen channel.

 Table below shows how to configure PORT A to either digital or analog I/O.

For example: configure only AN0 of PORT A as analog I/O while others are digital. An analog signal is send to AN0. The code should look like below:

ADCON0 = 0B00000001 //choose channel AN0

ADCON1 = 0B00001110  // only AN0 is analog

**ADON = turn ON ADC

**GO/DONE = conversion status

For PIC18, it is difference compare to PIC16 where PIC18 need to configure ADCON2.

ADCON2 = 0B10001010 is use for 22pF ceramic capacitor pair and 20MHz-40Mhz crystal.

The following steps should be followed to perform an A/D conversion:
1. Configure the A/D module:
• Configure analog pins, voltage reference and digital I/O (ADCON1)
• Select A/D input channel (ADCON0)
• Select A/D acquisition time (ADCON2)
• Select A/D conversion clock (ADCON2)
• Turn on A/D module (ADCON0)

2. Configure A/D interrupt (if desired):
• Clear ADIF bit
• Set ADIE bit
• Set GIE bit

3. Wait the required acquisition time (if required).

4. Start conversion:
• Set GO/DONE bit (ADCON0 register)

5. Wait for A/D conversion to complete, by either:
• Polling for the GO/DONE bit to be cleared
OR
• Waiting for the A/D interrupt

6. Read A/D Result registers (ADRESH:ADRESL); clear bit ADIF, if required.

7. For next conversion, go to step 1 or step 2, as required. The A/D conversion time per bit is defined as TAD. A minimum wait of 3 TAD is required before the next acquisition starts.

 

Color sensor + LCD with PIC16F877A

This is project the sense color and display on LCD. TCS3200 color sensor that fet output in frequency form according to color intensity is used. The higher the intensity, the higher frequency output is fet to PIC. In this project, I use only RED filter. So, the sensor only sensitive to object or surface with red element for example: red, orange, white. The video below shows how it works.

Switch controlled LED blinking

Video below shows LED light controlled by forward and reverse switch. When forward button is press, LED will shift to the right and reverse button will make the LED shift to the left. When LED is shifted until the last one, it will back to the first one again.

Programming part

//This is the desired array looks like
unsigned char _options[8]={0b00000001, 0b00000010, 0b00000100, 0b00001000,
  0b00010000, 0b00100000, 0b01000000, 0b10000000};
sel=0;  
PORTD =_options[sel]; //assign PORTD output to follow the array

//this is where button assigned to move forward or reverse
while(1)
{
if(forward==1)
{
if(sel==7) sel=0;
else sel++;
PORTD =_options[sel];
while(forward==1);         //waiting for button to be press
}


else if(reverse==1)
{
if(sel==0) sel=7;
else sel--;
PORTD =_options[sel];
while(reverse==1);
}

3x3x3 LED cube with PIC16F877A

This is the first LED cube i made using PIC16F877A and 27 pieces of LED and 3 pieces of diodes for reverse bias pervention. The following Video is the result of 15 types of simulations:

I had assigned the LED into 9 columns and 3 layer. This means 12 output is needed for the simulation. Below is the circuit for the PIC controller and the LED cube.

PIC controller circuit

LED cube circuit

The 3 layers LEDs are sharing cathode and soldered to diode 1N4001 before fed to the PIC output pins. This is to ensure there will be no reverse bias going through the LEDs as the reverse bias threshold voltage is 5V. This will damage the LED. The connections of diodes are as shown in figure below. Normally the anode of the resistor will fed to 90 ohm - 100 ohm resistor to reduce the output voltage to approximately 3.3V. There is no resistor fed from the output pins for my LED cube because the output voltage of 4.4V seems OK for the LED.

Diode connection from cathode

The coding for this cube is basic ON & OFF plus some delay. All port B plus 1 RD7 are used as columns and RD4-6 is used as layers for example:

This is the main part of the program. For other style can be add-on with adding extra code. (I upload in JPEG form because the coding become different due to the coding conflict with .html)





LED cube for 5x5x5 will be the next target after LEDs reach... >.< limitation of PIC16F877A... Looking for ways to make it 8x8x8 or even more...