Diff: main.cpp

Revision:

0:17804efd16c8

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu May 09 01:05:42 2013 +0000
@@ -0,0 +1,63 @@
+
+#include "mbed.h"
+
+PwmOut led(LED1); // led 1 indicates dim value
+DigitalOut led2(LED2); // led 2 indicates delay time for interrupts
+
+// pin for ZeroCross tail input
+// An external 1K pullup required
+InterruptIn zerocross(p27);
+
+// pin for PowerSSRtail output
+DigitalOut SSR(p21);
+
+//use timer interrupts to control dimming
+Timeout SSRtriggerOn;
+
+// dimmer value 0.0=off and 1.0=full on
+volatile float dim;
+
+// AC power line frequency
+const float powerlinefrequency=60.000;
+
+// this interrupt routine is activated after a time delay set by dim value
+void triggerOn()
+{
+    SSR = 1;
+    led2=0;
+}
+
+// this interrupt routine is activated by every AC line zero crossing
+// it is needed to synchronize the SCR turnon time delay to the AC line
+void dimmer()
+{
+    // turn off SSR at zero crossing
+    SSR = 0;
+    // compute time delay using dim value and set timer interrupt
+    // triggers SSR after a small post zero crossing time delay
+    SSRtriggerOn.attach(&triggerOn,(1.001-dim)/(2*powerlinefrequency));
+    led2=1;
+}
+
+int main()
+{
+    //set up interrupt routine to detect AC line zero crossings
+    zerocross.mode(PullNone);
+    wait(.2);
+    zerocross.rise(&dimmer);
+    // main program only sets dimmer level (dim)
+    // interrupt routines dim the light
+    while(1) {
+        //increase brightness
+        for(dim = 0.0; dim <= 1.0; dim += 0.025) {
+            led = dim;
+            wait(0.05);
+        }
+        //decrease brightness
+        for(dim = 1.0; dim >= 0.0; dim -= 0.025) {
+            led = dim;
+            wait(0.05);
+        }
+    }
+}
+