[sudo-discuss] multiple lamp dimming with a single arduino

robb, since we got the zero-crossing detection working, now it's a matter of deciding how many lamps to control with a single arduino. I believe this instructable shows software that doesn't rely on the chip's timer being tied to the triac control pins, meaning that it could be used to control 8 or more triacs with a single plain arduino. http://www.instructables.com/id/3-channel-Dimmerfader-for-Arduino-or-other-… /* AC Light Control Ryan McLaughlin &lt;ryanjmclaughlin(a)gmail.com&gt; with slight modifications */ #include <TimerOne.h> // http://www.arduino.cc/playground/Code/Timer1 #define PINS 3 volatile int pinCount[PINS]; // make volatile to make available in interrupt volatile boolean zero_cross=0; // Boolean to store a "switch" to tell us if we have crossed zero int AC_pins[] = {3,4,5}; // Stup the pin numbers int AC_dim[PINS]; // Holds Dimming levels (0-128) 0 = on, 128 = 0ff int freqStep = 78; // Set the delay for the frequency of power (65 for 60Hz, 78 for 50Hz) per step (using 128 steps) // freqStep may need some adjustment depending on your power the formula // you need to us is (500000/AC_freq)/NumSteps = freqStep void setup() { for(int a=0; a < PINS; a++) { //set the pins to output pinMode(AC_pins[a],OUTPUT); pinCount[a] = 0; // keeps track of the time in the cycle AC_dim[a] = 0; // dimming level set to zero } attachInterrupt(0, zero_cross_detect, FALLING); // Attach Interrupt to Pin 2 (interrupt 0) for Zero Cross Detection Serial.begin(9600); Timer1.initialize(freqStep); // Initialize TimerOne library for the freq we need Timer1.attachInterrupt(dim_check, freqStep); // Use the TimerOne Library to attach an interrupt // to the function we use to check to see if it is // the right time to fire the triac. This function // will now run every freqStep in microseconds. } void zero_cross_detect() { // function to be fired at the zero crossing zero_cross = 1; // set flag to tell dimming function zero cross has occured } // End zero_cross_detect void dim_check() { // Function will fire the triac at the proper time if(zero_cross == 1) { // First check to make sure the zero-cross has happened else do nothing for(int a=0; a < PINS; a++) { if(pinCount[a] >= AC_dim[a]) { // Check and see if i has reached the dimming value we want digitalWrite(AC_pins[a], HIGH); // Fire the Triac delayMicroseconds(5); // Pause briefly to ensure the triac turned on digitalWrite(AC_pins[a], LOW); // Turn off the Triac gate (Triac will turn off at the next zero cross) pinCount[a] = 0; // Reset the accumulator zero_cross = 0; // Reset the zero_cross so it may be turned on again at the next zero_cross_detect } else { pinCount[a]++; // If the dimming value has not been reached, incriment the counter } } } } void loop() { // This is simply making all outputs cycle through bright-dark, out of time with each other. for(int i=0; i<127; i ++) { for(int a=0; a < PINS; a++) { int ii = i+42; //this is the bit that puts the blinking lights out of sync with one another if(ii > 127) ii -= 127; AC_dim[a] = ii; } delay(50); } }