Timer1 question and AC Phase control

Hi,

Sorry for bumping my own thread but the last one seems to have been buried (see here: http://forum.arduino.cc/index.php?topic=298511.0

I have modified the AC Phase Control code given on the Arduino Playground to try and make a PID heater controller. I was instructed in the last thread that I should be making better use of Timer interrupts to trigger the triacs.

I have copied the code but I am really struggling with the timer firing and also understanding the purpose of PULSE shown below.

Basically, I just want to be able to control the power output from the Triac from 0-100% with a variable called Percent. How do I correlate this Timer based system with Percent going from 0-100% without having the code issues highlighted in the last thread?

Once that is implemented, I want to be able to set up a PID control loop with Setpoint being a chosen temperature, Input = thermistor reading and Output = Percent duty cycle of the Triac.

I just can’t seem to figure it out and understand how that OCR1A operates and controls the duty cycle.

Please help and thanks!

Barry

#include <avr/io.h>
#include <avr/interrupt.h>
#include <PID_v1.h>
#include <TimerOne.h>


#define THERM_PIN   0
int DETECT = 2;  
int GATE = 9;    //triac gate
int PULSE = 4;   //trigger pulse width (counts)
volatile int Percent;
int i=570;

//  double Setpoint, Input, Output;
//  PID myPID(&Input, &Output, &Setpoint,2,5,1, DIRECT);


const int temps[] PROGMEM = { 
  0, 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 
 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 
 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 68, 69, 70, 71, 72, 73, 74, 
 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 88, 89, 90, 91, 
 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 102, 103, 104, 105, 106, 
107, 108, 109, 110, 111, 112, 113, 114, 114, 115, 116, 117, 118, 119, 120, 
121, 122, 123, 124, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 
134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 143, 144, 145, 146, 147, 
148, 149, 150, 151, 151, 152, 153, 154, 155, 156, 157, 158, 159, 159, 160, 
161, 162, 163, 164, 165, 166, 167, 167, 168, 169, 170, 171, 172, 173, 174, 
175, 175, 176, 177, 178, 179, 180, 181, 182, 182, 183, 184, 185, 186, 187, 
188, 189, 190, 190, 191, 192, 193, 194, 195, 196, 197, 197, 198, 199, 200, 
201, 202, 203, 204, 205, 205, 206, 207, 208, 209, 210, 211, 212, 212, 213,
214, 215, 216, 217, 218, 219, 220, 220, 221, 222, 223, 224, 225, 226, 227, 
228, 228, 229, 230, 231, 232, 233, 234, 235, 235, 236, 237, 238, 239, 240, 
241, 242, 243, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 252, 253, 
254, 255, 256, 257, 258, 259, 260, 260, 261, 262, 263, 264, 265, 266, 267, 
268, 269, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 279, 280, 
281, 282, 283, 284, 285, 286, 287, 288, 289, 289, 290, 291, 292, 293, 294, 
295, 296, 297, 298, 299, 300, 301, 301, 302, 303, 304, 305, 306, 307, 308, 
309, 310, 311, 312, 313, 314, 315, 315, 316, 317, 318, 319, 320, 321, 322, 
323, 324, 325, 326, 327, 328, 329, 330, 331, 332, 333, 334, 335, 335, 336, 
337, 338, 339, 340, 341, 342, 343, 344, 345, 346, 347, 348, 349, 350, 351, 
352, 353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 
367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 
382, 383, 384, 385, 386, 387, 388, 389, 390, 392, 393, 394, 395, 396, 397, 
398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 410, 411, 412, 413, 
414, 415, 416, 417, 418, 419, 420, 422, 423, 424, 425, 426, 427, 428, 429, 
430, 432, 433, 434, 435, 436, 437, 438, 439, 441, 442, 443, 444, 445, 446, 
448, 449, 450, 451, 452, 453, 455, 456, 457, 458, 459, 460, 462, 463, 464, 
465, 466, 468, 469, 470, 471, 472, 474, 475, 476, 477, 479, 480, 481, 482, 
484, 485, 486, 487, 489, 490, 491, 492, 494, 495, 496, 498, 499, 500, 501, 
503, 504, 505, 507, 508, 509, 511, 512, 513, 515, 516, 517, 519, 520, 521, 
523, 524, 525, 527, 528, 530, 531, 532, 534, 535, 537, 538, 539, 541, 542, 
544, 545, 547, 548, 550, 551, 552, 554, 555, 557, 558, 560, 561, 563, 564, 
566, 567, 569, 570, 572, 574, 575, 577, 578, 580, 581, 583, 585, 586, 588, 
589, 591, 593, 594, 596, 598, 599, 601, 603, 604, 606, 608, 609, 611, 613, 
614, 616, 618, 620, 621, 623, 625, 627, 628, 630, 632, 634, 636, 638, 639, 
641, 643, 645, 647, 649, 651, 653, 654, 656, 658, 660, 662, 664, 666, 668, 
670, 672, 674, 676, 678, 680, 683, 685, 687, 689, 691, 693, 695, 697, 700, 
702, 704, 706, 708, 711, 713, 715, 718, 720, 722, 725, 727, 729, 732, 734, 
737, 739, 741, 744, 746, 749, 752, 754, 757, 759, 762, 764, 767, 770, 773,
775, 778, 781, 784, 786, 789, 792, 795, 798, 801, 804, 807, 810, 813, 816, 
819, 822, 825, 829, 832, 835, 838, 842, 845, 848, 852, 855, 859, 862, 866, 
869, 873, 877, 881, 884, 888, 892, 896, 900, 904, 908, 912, 916, 920, 925, 
929, 933, 938, 942, 947, 952, 956, 961, 966, 971, 976, 981, 986, 991, 997, 
1002, 1007, 1013, 1019, 1024, 1030, 1036, 1042, 1049, 1055, 1061, 1068, 1075, 
1082, 1088, 1096, 1103, 1110, 1118, 1126, 1134, 1142, 1150, 1159, 1168, 1177, 
1186, 1196, 1206, 1216, 1226, 1237, 1248, 1260, 1272, 1284, 1297, 1310, 1324, 
1338, 1353, 1369, 1385, 1402, 1420, 1439, 1459, 1480, 1502 };

static int power_lut_50Hz[100] = {
  200 ,   1161,   1472,   1694,   1872,   2022,   2155,   2277,   2388,   2494,
  2594,   2683,   2772,   2855,   2933,   3011,   3088,   3161,   3233,   3299,
  3366,   3433,   3494,   3555,   3616,   3677,   3738,   3794,   3855,   3911,
  3966,   4022,   4077,   4133,   4183,   4238,   4288,   4344,   4394,   4444,
  4500,   4550,   4600,   4650,   4700,   4750,   4800,   4850,   4900,   4949,
  5000,   5055,   5105,   5155,   5205,   5255,   5305,   5355,   5405,   5455,
  5505,   5561,   5611,   5661,   5716,   5766,   5822,   5872,   5927,   5983,
  6038,   6094,   6150,   6211,   6266,   6327,   6388,   6450,   6511,   6572,
  6638,   6705,   6772,   6844,   6916,   6994,   7072,   7149,   7233,   7322,
  7411,   7511,   7616,   7727,   7850,   7983,   8133,   8311,   8533,   8844,
};

void setup(){

 
  Percent = 100;
  // set up pins
  Serial.begin(9600);
  pinMode(DETECT, INPUT);     //zero cross detect
  digitalWrite(DETECT, HIGH); //enable pull-up resistor
  pinMode(GATE, OUTPUT);      //triac gate control
  attachInterrupt(0,zeroCrossingInterrupt, RISING);    
  
  // set up Timer1 
  //(see ATMEGA 328 data sheet pg 134 for more details)
  OCR1A = 100;      //initialize the comparator
  TIMSK1 = 0x03;    //enable comparator A and overflow interrupts
  TCCR1A = 0x00;    //timer control registers set for
  TCCR1B = 0x00;    //normal operation, timer disabled
  
  
  
//  myPID.SetMode(AUTOMATIC);
//  Setpoint = 250;

}  


void zeroCrossingInterrupt(){ //zero cross detect   
  TCCR1B=0x04; //start timer with divide by 256 input
  TCNT1 = 0;   //reset timer - count from zero
}

ISR(TIMER1_COMPA_vect){ //comparator match
  digitalWrite(GATE,HIGH);  //set triac gate to high
  TCNT1 = 65536-PULSE;      //trigger pulse width
}

ISR(TIMER1_OVF_vect){ //timer1 overflow
  digitalWrite(GATE,LOW); //turn off triac gate
  TCCR1B = 0x00;          //disable timer stopd unintended triggers
}                            





void loop(){ 
  
i--;
OCR1A = i;     //set the compare register brightness desired.   
if (i<5){i=548;}
delay(15);

int therm;                                             //Thermistor Reading & Conversion  

therm=analogRead(THERM_PIN)-238;
therm=pgm_read_word(&temps[therm]);                    //Thermistor Reading & Conversion  

//delay(1000);
//Serial.println(therm,DEC);                          




// myPID.Compute();   
 }