N-Channel MOSFET - Current driver

Other Hardware General Electronics
6

Hi,
The scope does show the varying PWM from the ATiny85. It also shows the 12V on the drain of the MOSFET. The supply voltage to the damper is a nominal 12V DC.
The damper is an inductive load. I don't have the spec of the damper unfortunatly.
The ATiny ground and damper ground are shared.
Damper Current Controller.pdf (242.3 KB)

/*
                              ATtiny85
                           -------u-------
       RST - A0 - (D 5) --| 1 PB5   VCC 8 |-- +5V
                          |               |
500Hz SW I/P A3 - (D 3) --| 2 PB3   PB2 7 |-- (D 2) - A1  --> 10K Potentiometer
                          |               |
1kHZ SW I/P  A2 - (D 4) --| 3 PB4   PB1 6 |-- (D 1) - PWM --> Damper Circuitry
                          |               |
                   Gnd ---| 4 GND   PB0 5 |-- (D 0) - PWM --> 2Khz SW I/P 
                          -----------------
*/

// normal delay() won't work anymore because we are changing Timer1 behavior
// Adds delay_ms and delay_us functions
#include <util/delay.h>

// Clock at 8mHz
#define F_CPU 8000000  //F_CPU 8000000. This is used by delay.h library

const int PWMPin = 1;  // Only works with Pin 1(PB1)
const int PotPin = A1;
const int fivehundredhertz_select = 3;
const int onekilohertz_select = 4;
const int twokilohertz_select = 0;

// variables will change:
int selectionState1 = 0;// variable for reading the 500Hz selection
int selectionState2 = 0;// variable for reading the 1KHz selection
int selectionState3 = 0;// variable for reading the 2KHz selection

void setup()
{
  pinMode(PWMPin, OUTPUT);
  pinMode(fivehundredhertz_select, INPUT);
  pinMode(onekilohertz_select, INPUT);
  pinMode(twokilohertz_select, INPUT);

  //Use FAST PWM
  TCCR0A = 1 << COM0B1 | 0 << COM0B0 | 1 << WGM01 | 1 << WGM00;
  TCCR0B = 1 << WGM02;

  /*
     8 000 000 / 64 = 125 kHz
    64 - pre-scaler
    125 kHz / 63 ~ 2000 Hz
    63 - OCR0A
  */
  // disable interrupts
  TIMSK = 0;

  // set TOP to generate ~2 kHz
  OCR0A = 63;// 63=2Khz, 127=1Khz, 500hz=255

  // 50% duty cycle
  OCR0B = 31;//31

  // start timer at 125 kHz (8 MHz / 64)
  TCCR0B = 1 << WGM02 | 0 << CS02 | 1 << CS01 | 1 << CS00;

}

void loop()
{
  int in, out;

  in = analogRead(PotPin);

  //  out = map(in, 0, 1023, 0, 63);//(in, 0, 1023, 0, 1023) LINE ADDED

  // read the state of the input selections:
  selectionState1 = digitalRead(fivehundredhertz_select);
  selectionState2 = digitalRead(onekilohertz_select);
  selectionState3 = digitalRead(twokilohertz_select);
  if (selectionState1 == HIGH)
  {
    OCR0A = 255;//500 hz
    out = map(in, 0, 1023, 0, 255);//(in, 0, 1023, 0, 255)
  }
  else
  {
    ;//Do nothing
  }

  if (selectionState2 == HIGH)
  {
    OCR0A = 127;//1Khz(127)
    out = map(in, 0, 1023, 0, 127);//(in, 0, 1023, 0, 127)
  }
  else
  {
    ;//Do nothing
  }

  if (selectionState3 == HIGH)
  {
    OCR0A = 63;//2Khz 63
    out = map(in, 0, 1023, 0, 63);//(in, 0, 1023, 0, 1023)
  }
  else
  {
    ;//Do nothing
  }


  if ( out < 0.5 )  pinMode(PWMPin, INPUT);   // This was added due to duty cycle only reaching as low as 1% min.
  else pinMode(PWMPin, OUTPUT);
  OCR0B = out;
  _delay_ms(200);
}